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==APEX==

Jeff, good job on the APEX and Lv stuff.  Thanks.  [[User:Dicklyon|Dicklyon]] 04:40, 20 July 2006 (UTC)
: Thanks, Dick. I've made a corresponding edit of the entry for exposure value.

Jeff, why the "criscam" link?  I don't see anything about EV there.  By the way, I've used the Kyoritsu light box and patterns.  I understand one can use it simulating lux levels, testing meter calibration, etc., but I still don't see how it's a usefil artical external link.  Looks more like link spam. [[User:Dicklyon|Dicklyon]] 21:55, 19 August 2006 (UTC)
:Dick, there actually is mention of EV, LV, and K in the C.R.I.S. link, under "kyoritsu test equipment," so I've restored the link. The link was included simply to show that I didn't pull the Kyoritsu references in the test out of the air. I hope this addresses your comment.
[[User:JeffConrad|JeffConrad]] 22:05, 19 August 2006 (UTC)

::Thanks, Jeff.  The other way to do this is to put the link in single-brackets at the end of the statement that needs a citation.  The external links sections is for more general further reading and such. See also my comments on the EV talk. [[User:Dicklyon|Dicklyon]] 22:14, 19 August 2006 (UTC)
:::I used the current approach for two reasons: 1) All other in-text references use author-date, and 2) the C.R.I.S. link isn't really a direct reference, and I felt an in-text link that points only to the site might be confusing. [[User:JeffConrad|JeffConrad]] 01:59, 20 August 2006 (UTC)

==Light value==

This entry still isn't complete (or quite correct). The APEX section in Stroebel, Compton, Current, and Zakia (2000) is more than a bit confused: the text refers to "scene illuminance," and Table 2-3 on the next page uses units of illuminance (with the curious symbol Bv), but the example uses units of luminance, and the defining equation uses the symbol Lv. Although it probably was not the intent, this reference technically uses "light value" as a synonym for both incident-light value and luminance value. Consequently, I think we need to restore mention of incident light. I'm ready to do this, but I'd like to be sure that the usage in Zakia and Stroebel (1993) also is correct. I'm wondering if the table in Stroebel et. al. (2000) was copied from from Zakia and Stroebel (1993). I don't have a copy of that reference--do you (I noticed that you added it)?

:Jeff, is this comment you wrote to yourself intended for me?  The history says someone else added those refs, but I think I have the 1993 encyclopedia (I'll check in the office on Monday), and the other is available (partly) on google book search: [http://books.google.com/books?vid=ISBN0240804058&id=BRYa6Qpsw48C&pg=PA53&lpg=PA53&vq=light-value&dq=inauthor:Zakia+inauthor:Stroebel&sig=6DcqeloZn2hYdBIu_uVOo-RPzY4]. [[User:Dicklyon|Dicklyon]] 03:44, 20 August 2006 (UTC)

::Dick, indeed ... I forgot the salutation. I also wasn't too clear in the note--I added those references to "light value" when I removed all discussion of "light value" from the "APEX system" article. What I meant to say was that it looks like you added Zakia (1993) to the APEX system article on 25 June 2006. I seem to be getting as confused as the meaning of "light value" ... [[User:JeffConrad|JeffConrad]] 07:01, 20 August 2006 (UTC)

:::That sounds right, then.  That must be the edition I have at work then (I also have a much older hardbound edition, if that's of any interest).  What shall I check?  Or should I send you a copy of relevant pages? [[User:Dicklyon|Dicklyon]] 07:33, 20 August 2006 (UTC)
::::Dick, given the variety of meanings, it would be interesting to see if the new and old versions agree. I'd love to see the relevant pages, but providing them seems like a lot of extra work. It would seem to me that three issues might be relevant:
::::#Did the definition(s) refer to incident or reflected light?
::::#Was the definition consistent with APEX (either incident-light value or luminance value)?
::::#What symbol was used (<math>I_v</math>, <math>B_v</math>, <math>L_v</math>, or even something else)?
::::[[User:JeffConrad|JeffConrad]] 23:36, 20 August 2006 (UTC)
:::::#"light level in footcandles divided by 6".  That's luminance, reflected, right (candela per sq. foot)?
:::::#It's consistent with APEX luminance value Bv.
:::::#Bv.  
:::::Basically, they treat Light value as a synonym for Brightness value, and that's all.  The entry was written by a J. Johnson. Their entry on the Additive system also says "Light value (Bv)". [[User:Dicklyon|Dicklyon]] 17:06, 21 August 2006 (UTC)

::::::Dick, thanks for the info. Footcandles are units of <em>illuminance</em>. The expression <math>B/6</math> is consistent with that, and is the same expression used in the table in Stroebel et. al. (2000). In other words, this definition is equivalent to ''incident-light value''; inexplicably, they use the symbol (<math>B_v</math>) for ''luminance value,'' when <math>I_v</math> would have seemed more appropriate. What a mess ... If this can confuse the likes of Stroebel and Zakia, I shudder to think what it does to most others.

::::::Even the mention of "illuminance" is potentially a can of worms, because it properly refers to flux density incident upon a flat surface, and is properly measured with a flat (cosine-responding) sensor. The median APEX value of 20.8 for the incident-light calibration constant (and the expression <math>B/6</math>) also implies a flat sensor. This, of course, usually isn't the best way to take an incident-light reading of a typical scene. The more commonly used "illuminance" measured with a hemispherical sensor requires a different calibration constant and a different expression for relating illuminance to incident-light value. I'm not so sure I want to open the can at present, so I'm disinclined to even mention the sensor type. The same issue applies to the exposure value article, because EV can be a measure of illuminance as well as luminance. I somewhat cover this in an  [http://www.largeformatphotography.info/articles/conrad-meter-cal.pdf article] (in PDF) on the Large-Format site, though this issue is buried in the other content. I could add the link to the Wiki article, but I'm not sure whether it would be more likely to inform or confuse.

::::::Incidentally, it's obvious from the APEX equations that <math>B_v</math> and <math>I_v</math> are numerically equal, so that the same camera settings will result from using either. Nonetheless, the physical quantities are quite different, and I find the accompanying imprecision discomforting. NPOV and "no original research" preclude tagging "light value" as deprecated, but a comprehensive factual treatment hopefully will lead many readers to that conclusion.

::::::I'll try to describe the confusion in a tactful way in the new edit. I think it's worth pursuing this until we get it right because the primary sources (e.g., most of the ASA and ANSI standards that I've cited) are becoming increasingly difficult to obtain. [[User:JeffConrad|JeffConrad]] 02:02, 22 August 2006 (UTC)
 
Suffice it to say that "light value" has had so many meanings that essentially it is meaningless, and would seem an inadvisable substitute for "EV at ISO 100," however inelegant that expression may be.  [[User:JeffConrad|JeffConrad]] 01:59, 20 August 2006 (UTC)

== Re: DOF article ==

Hi Jeff!<br>
Thanks for bringing that up, I think this is what you were after? [[:Image:Wolf spider single frame.jpg]] --[[User:Fir0002|Fir0002]] 22:46, 19 December 2006 (UTC)

:I'll add this to the article&mdash;I think it will make the benefits of compositing more obvious. I assume it was taken at f/11; do you know the approximate magnification? [[User:JeffConrad|JeffConrad]] 00:26, 20 December 2006 (UTC)

::Whoops sorry Jeff, I'm used to people replying back on my talk page. Anyway doesn't matter. Image was taken at f/11, not sure what you mean by magnification, but it was almost at my minimum focal distance (1:1) --[[User:Fir0002|Fir0002]] 23:09, 23 December 2006 (UTC)

:::Magnification is another way of stating reproduction ratio; it's the ratio of image to the object size. If, by your reply, you indicate a reproduction ratio of 1:1, the magnification was 1.0.
:::Magnification is more common than reproduction ratio in DoF formulae. Knowing the magnification here is informative because it illustrates just how shallow the single-shot DoF is. Look at the formula under Closeup DOF (under DOF formulae); assume, for sake of argument, that an appropriate value for the circle of confusion <var>c</var> with your 20D is 0.020&nbsp;mm. Then, for a symmetrical lens,

::::<math>\mathrm {DOF} \approx 2 \times 11 \times 0.020\; \mathrm {mm} \times \frac {1 + 1} {1^2} = 0.88 \; \mathrm { mm}</math>

:::The need for the multiple exposures becomes quite obvious. If, indeed, the magnification was approximately 1, I'll add mention of that to the DOF article. [[User:JeffConrad|JeffConrad]] 00:06, 24 December 2006 (UTC)

Hi Jeff - 
I am the user that made the two edits on the [[Depth of Field]] on 12/28/2010 changing "increases" to "decreases". The reason I made those edits was to make the article more consistent as it contradicts itself. I have added my explanation to the Talk page of the article.  [[Talk:Depth of field]]  Please feel free to respond.  Thanks!  
[[User:Hergio|Hergio]] ([[User talk:Hergio|talk]]) 18:22, 28 December 2010 (UTC)

== Quotes ==

I don't want to get into an edit war, but I can't see what possible advantage the existing quotes at [[light value]] could have. For one, the punctuation is incorrectly located, according to [[WP:MOS]] (see also [[WP:REF]] for reference punctuation). Two, it makes reading the markup more difficult (necessary markup is one thing; obfuscation is another). Three, the article isn't even internally consistent (normal non-curly quotes were already used in several places). If you feel strongly that the curly quotes must be used (personally, I loathe them, but as there's no consensus either way...), at least consider using the toolbar characters (“”) for readability and fixing the punctuation location. --[[User:Fru1tbat|Fru1tbat]] 03:56, 26 January 2007 (UTC)
:Note: I posted that before I read your comment on the article's talk page, so I concede that I wasn't considering print appearance as a possible advantage... --[[User:Fru1tbat|Fru1tbat]] 04:10, 26 January 2007 (UTC)

:A quick glance at many WP articles appears to reveal a strong preference for neutral quotes. However, this would be considered bad typography by almost any standard. The neutral quote had a relatively brief lifetime&mdash;from the invention of the typewriter in 1870 until whenever one considers the date of the typewriter's obsolescence. That the appearance of the neutral quotes is reasonable with the current Wikipedia sans-serif font is coincidence. Were Wikipedia to change to a different font at some time in the future, the appearance might not be as acceptable, even with some sans-serif fonts. With almost all serif fonts, the appearance would be unacceptable.

:I'm no more fond of typing (or reading) HTML entities than you are, but they do have some advantages, one of which is that they seldom cause trouble. There probably is something to be said for putting everything in Unicode (as with inputting the characters from the links under the edit box), but there also are some difficulties. It's a bit of a pain to reach for the links, and doing so is not possible when composing the edit with an external editor (as I often do. Wikpedia's editing facilities might kindly be described as limited ...). There ought to be an easier method of inputting opening and closing quotes; 30 years ago, troff recognized `` as an opening quote. Admittedly, Wiki's use of <nowiki>''</nowiki> to indicate start and end of italics presents a bit of an obstacle.

:It looks as though I forgot about WP's use of international rather than U.S. practice for positioning punctuation. However, that article also states
::However, insisting on changing to this usage, especially in articles written in American English, is deprecated; there are better and less divisive uses of time.
:With all due respect, this would seem to border on a "Pointless edit," which you specifically disavow.

::Good point, and I try not to change/fix punctuation unless I'm fixing something more important with the same edit, but the problem with the term "pointless edit" is that it's too subjective. The line you quoted from the MoS was added recently, IIRC, and I think it unnecessarily weakens the guideline. I believe making things like punctuation and grammar consistent across Wikipedia contributes ''significantly'' to making it appear more "professional", and that's important to me. That being said, there are certain instances that I consider more egregious than others. The [[WP:MOS-T]] section on punctuation is worded with less room for variation, for example.

:I have no real objection to your changing position of the punctuation (or changing the HTML quotes to Unicode), but I have better uses of my time. I hate to invest more time preparing for possible code maintenance than I'm likely to actually spend on code maintenance. In the future, I'll follow the WP guideline on punctuation and quotation marks when starting from scratch. In terms of existing material, though, this would seem more suited to a bot. It would not surprise me if such a bot already exists. Many years ago, I had the equivalent of a bot that would put commas and periods ''inside'' quotation marks. [[User:JeffConrad|JeffConrad]] 06:12, 26 January 2007 (UTC)

::I made the edit because I happened across the article and wanted to try to improve it, and I only complained because I felt that reverting did more harm than good, but it won't bother me all that much if it's not "my way". I have a text editor that supports the Unicode characters, and if you want, I could do a quick global replace to at least substitute for the HTML code, but I'd be content to leave it alone. --[[User:Fru1tbat|Fru1tbat]] 14:02, 26 January 2007 (UTC)

:::I agree that consistency makes articles look more professional, but I'd put consistency of punctuation (American vs. international style) far behind differences between British and American syntax and spelling. Even more significant is inconsistency of style among multiple authors. It's a minor factor in the Light value article because I've written most of it, and revised the rest for consistency. The [[Depth of field]] article is another matter; there have been so many contributors (of widely varying technical and writing ability) that it's more of a hodgepodge than an article. In my opinion, it doesn't deserve an A rating in its present form.

:::In any event, I've changed the positions of commas and periods in the [[Light value]] article to conform to the MoS. It takes more effort to argue than to change it. Although it's not a major issue, I'd rather leave the quotes as they are; I also could make global substitutions, but the Unicode quotes make future edits more difficult for me (some other editor functions don't handle Unicode). [[User:JeffConrad|JeffConrad]] 19:59, 26 January 2007 (UTC)

== Depth of field FAC prep ==

Jeff, I just wanted to say thanks for the great work on the article. It looks to me like it could very easily be turned into an FA-class article in a short time. I'm not the expert on the topic that you are, but all I can see that is deficient at the moment is the amount of inline citations. What are your thoughts, and would you be willing to shepherd the article to the gold star? :) [[User:Girolamo Savonarola|Girolamo Savonarola]] 22:43, 10 September 2007 (UTC)

:Girolamo, I think the article is OK, but I don't know if quite share your high opinion of it. There have been a few additions about which I am not enthusiastic, and there is at least one link to a WP article that I think has seriously flawed technical content. It's also a bit embarrassing when someone feels the need to use Maple to check a fix to a typo (actually, I had botched a copy and paste) in a formula—I probably should carefully review all formulas to ensure that there aren't other errors. I'd also feel better if at least one other significant contributor (e.g., Dick Lyon) has the same confidence in the article.
:One question: what is your concern about the inline citations, and how should they be fixed? Some of the hyperlinks are simply to the References section. [[User:JeffConrad|JeffConrad]] 23:50, 10 September 2007 (UTC)

::Well, as I said, you know the topic far better than I could possibly aspire to, so I'll have to take your word for it. I've already spoken to Dick, and told me that he didn't feel up to the task of leading this to FAC himself and recommended you (although I'd messaged both of you simultaneously). I have no idea what his thoughts on its state are, however.
::The inline citations need to be handled, well...inline. Having external links inside the body itself is generally considered bad style - they need to be replaced by ref tags, which can include the links inside there. You can see [[Wp:cite#Footnotes]] for more details. [[User:Girolamo Savonarola|Girolamo Savonarola]] 22:52, 11 September 2007 (UTC)

:::I've asked Dick for his opinion.
:::I see only a handful of external links in the text (links to Jacobson's, van Walree's, and my writings—are these the links to which you refer?); it would be a simple matter to remove them (the links are in External references anyway). Links such as (Langford 1973, 81) in '''Limited DOF: selective focus''' can't really be changed, though; the article uses the author-date system (“Harvard referencing” to some Wikipedians) of references plus footnotes (via ref tags)—see [[WP:CITE#Maintaining a separate "References" section in addition to "Notes"|Maintaining a separate "References" section in addition to “Notes”]] in the article you cited. Converting the author-date references to ref tags would merge the two, making a real mess of things. The author-date links used work to much the same effect as [[Template:Harv]] and [[Template:Citation]], though the formatting of references follows the ''Chicago Manual of Style'' (and admittedly, the inline HTML looks a bit ugly to the editor). [[User:JeffConrad|JeffConrad]] 00:14, 12 September 2007 (UTC)

::::Well, I'll leave it to you; it's just something I anticipate may be mentioned by reviewing editors. You might want to also run the article by the [[WP:PR|general peer review]] for preliminary comments and touch-ups. As for content deficiencies, as I've mentioned, I'm not equipped to gauge them, but please be bold and tackle what you can see. I look forward to seeing what develops! :) [[User:Girolamo Savonarola|Girolamo Savonarola]] 00:22, 12 September 2007 (UTC)

== Entrance pupil ==

Jeff, I don't mind that you took entrance pupil out of my DOF edit, but your reason is wrong.  The exit pupil size and position determine depth of focus; but the entrance pupil size and position determine the depth of field; this is most obvious in the object field method.  Of course, they turn out equivalent, too, since the f-number is the same whether you base it on one or the other, no?  [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 01:04, 8 June 2008 (UTC)

:Dick, I'm not sure I agree. The exit pupil is the center of projection, and the only view of the aperture seen by the image plane. I think I show this fairly clearly in the section Depth of Field for an Asymmetrical Lens in my paper linked in the DOF article. The ultimate expression commonly used gives the DoF in terms of the entrance pupil (via the f-number), but the entrance pupil diameter multiplied by pupillary magnification gives the exit pupil diameter. If the exit pupil weren't the governing factor, we could ignore the pupillary magnification in closeup DoF equations. Sidney Ray also covers this in the work linked in the article, but doesn't specifically derive the DoF for an asymmetrical lens, so you need to examine material in Sections 14.1.5, 22.2.1, and 22.4.1. David Jacobson implies the same in defining effective f-number in terms of the eXit pupil. Ultimately, the DoF is determined by the aperture diameter, regardless of how we choose to describe it, so we're safe with the current wording.

:In any event, I think the article is more accessible to the average reader with the revision to emphasize aperture over f-number. Also, in checking Jacobson's tutorial, I discovered that it has moved (to a version revised in 2007), so I fixed the link. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 03:23, 8 June 2008 (UTC)

::Well, take another look at my [http://dicklyon.com/tech/Photography/DepthOfField-Lyon.pdf DOF draft] and tell if you don't agree that the outside-the-box is much simpler, and has to be equivalent to any other method that works.  The article is fine as is. [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 05:52, 8 June 2008 (UTC)

:::Actually, I don't find it simpler, but it may just be a matter of personal preference and what I am accustomed to. I still don't see how one can avoid mention of the pupillary magnification when the aperture is given in terms of the f-number (or the absolute entrance pupil diameter), because without the pupillary magnification, one simply cannot arrive at the universally accepted closeup DoF equations. Perhaps, though, it is simply as you indicate in your paper

::::The formula 2''SC''/''md'' is exact, as long as ''S'' is measured from the entrance pupil, but the equations with ''N'' may need adjustments.

:::Van Walree, David Jacobson, Sidney Ray, and I all come up with the same closeup equations, and absent a vast conspiracy, it's unlikely we'd all make the same mistake. I'm sure that with a little mathematical rearrangement, it's possible to show that your equations are equivalent to mine.  I shall leave that as an exercise for the reader :-).

:::In any event, I agree that the article (or at least this section) is fine as it is. For most readers (and most photographic situations), the distinction among aperture, entrance pupil, and exit pupil is irrelevant and quite possibly confusing. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 07:57, 8 June 2008 (UTC)

::::I'm not claiming the equations are equivalent; I suppose it's possible, if your focal length, f-number, and pupillary magnifiation imply an entrance pupil position, but I'm not at all sure; I am saying, however, that they should give the same answer, for the same physical setup.  If my equation is correct and exact as I claim, you can see why I claim that using entrance pupil diameter is the simplest approach (as von Rohr had concluded before me); it leaves you without any worries about f-number, focal length, pupillary magnification, or anything else about the lens.  So, let's cook up a real example and see...  [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 14:53, 8 June 2008 (UTC)

:::::I don't see how our equations could not be equivalent unless one of them is wrong.  Pupil magnification indeed implies pupil locations relative to the nodal planes; I illustrate this in Figures 2 through 4 in my paper (the figures aren't strictly geometrically accurate; I moved some things around a bit to make it easier to label the distances, but my analysis doesn't depend on geometrical accuracy of the diagram).

:::::How would we cook up a real-world example?  I suspect that with either a symmetrical lens or large camera-to-subject distance, we'd probably get the same answer, because the object nodal plane, entrance pupil, and exit pupil are all in the same place.  With a highly asymmetrical lens at closeup distance, our results would probably differ. To be honest, I've never found calculations of much help in closeup work, and pretty much do everything visually. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 03:45, 9 June 2008 (UTC)

::::::Agreed.  Still, it would be fun to check the equations on a close-up asymmetric lens problem, and see if they give the same answer.  I expect they will, and if they don't then we'll learn something.  Maybe one of us got something wrong?  Maybe not?  Of course, if they match that doesn't imply anything strongly, but it suggests that maybe we both got it right. [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 04:11, 9 June 2008 (UTC)

===Equivalence of equations===

The equations are indeed equivalent, as they had to be. From my Figure 4 on p. 21, your distance <math>S</math> is

:<math>S = u + x_\mathrm {ep}</math> ,

where <math>x_\mathrm {ep}</math> is the distance from the front principal plane to the entrance pupil. Using my Eq.&nbsp;(81) for <math>x_\mathrm {ep}</math>, and making appropriate substitutions for <math>S</math> and <math>d</math> in the difference of your equations for <math>S_\mathrm{F}</math> and <math>S_\mathrm{N}</math> gives my Eq.&nbsp;(104), which reduces to Eq.&nbsp;(105) when the subject distance is much less than the hyperfocal distance. Direct substitution into your approximate closeup expression 2''SC''/''md'' also gives my Eq. (105). Note that ''c'' in my Eqs. (104) and (105) is the same as your ''C''. 

So is DoF determined by the entrance pupil or by the exit pupil? I guess it depends on how you approach it. The safest approach is probably to say that it's determined by the aperture, as the article currently does. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 07:19, 10 June 2008 (UTC)

:I agree there.  My preference for the entrance pupil approach is based on the fact that it makes it explicit that everything behind that can be safely ignored; the estrance pupil of a camera can be measured from the outside by looking at it, and if you also get the field of view (say from a test shot or electronic preview), then you have all you need, and can safely ignore focal length, f-number, and pupillary magnification.  And the equation is super simple, and very easy to derive.  But practically, you can get a good result with the "inside" parameters you're usually told (focal length, format size, f-number), and can usually get away with ignoring pupil magnification except in extreme cases.  As for "equivalent", not quite.  Your equations imply mine, as you showed; but mine don't imply yours since mine don't have enough parameters to describe the more specific cameras that yours apply to; but given some extra stuff, yes, they come out equivalent.  Thanks for checking.  [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 14:52, 10 June 2008 (UTC)

== Exposure (photography) ==

Jeff, my apologies it this is a faux pas, but I wanted to ask if you might be willing to help resolve some recent issues in the [[exposure (photography)]] article. I understand perfectly well if you would prefer to not get involved (please feel free to delete this section from your talk page), but I hope your contribution might carry some weight. I feel very awkward about asking you like this, but I don't what else to do for the best. Thanks for looking in ;)

The latest diff can be found here[http://en.wikipedia.org/w/index.php?title=Exposure_(photography)&diff=270832032&oldid=270801086] and there is a considerable amount of discussion scattered around the discussion page. The conflicts began after I posted this contribution[http://en.wikipedia.org/w/index.php?title=Exposure_(photography)&diff=270132561&oldid=266133383] although I later replaced the section I had overwritten with this version[http://en.wikipedia.org/w/index.php?title=Exposure_(photography)&diff=270483106&oldid=270254781] in the hope of ending the dispute. --[[User:Redbobblehat|Redbobblehat]] ([[User talk:Redbobblehat|talk]]) 19:16, 15 February 2009 (UTC)

:I made one minor change to the article and made several comments on the talk page as well as on your talk page. It does seem that the discussion is almost becoming an argument for argument's sake; as always, it takes two to tango. I've not been involved with this article, and I'm not sure I want to jump into an extended debate. I think the article has considerable room for improvement, perhaps more in terms of clarification than adding new material. In general, I'd recommend keeping to the mainstream, well-documented, and objective as much as possible. Discussion on the talk page prior to major edits on which there is likely to be disagreement will almost certainly help. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 03:37, 16 February 2009 (UTC)

:: Jeff, many thanks for stepping into a difficult situation. I fully accept it does take two to tango, and I can certainly make no claim to be a model of stoic virtue, or an irrefutable expert on photography (alas!). After your comments last night I really thought we had all made some progress, but in the cold light of day it seems that nothing has changed. I'm very sorry to have wasted your time. Thanks again. --[[User:Redbobblehat|Redbobblehat]] ([[User talk:Redbobblehat|talk]]) 23:20, 16 February 2009 (UTC)

:::I'm not sure it's as dire as you seem to see it. You made some pretty substantial changes to articles in which you had no previous involvement; there's nothing necessarily wrong with this—Wikipedia urges editors to “[[Wikipedia:Be bold|be bold]]”. But when the changes encounter considerable resistance, it's often better to discuss planned additional changes before making them. It can be frustrating at times because a suggestion on the talk page often gets no response. When that happens, I often just go ahead with what I have suggested; if it draws objections, I deal with them as best I can. But the first step is to give an outline of what you have in mind—at least then you can't be accused of a sneak attack. I do agree with Dick that changes should be well thought out and documented wherever possible. As I said, the Exposure article, like most others on photography, could use improvement. Many of these articles have had some contributions by people with marginal knowledge of the subjects, and sorting it all out is not an easy or rapid process. A fair number of contributions have been utter nonsense, and I think some of those (certainly including Dick and me) who have made significant contributions to an article develop a pretty wary eye for changes. The objective, as always, is to have articles that provide accurate, useful information to the reader. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 01:56, 17 February 2009 (UTC)

:::One additional thought: there seem to be several topics on which you're still working to get a full understanding. It's best to make sure that you really have a solid understanding before making an edit. Consulting good sources (which you seem to do) is an excellent start, but sometimes it takes a second look (or more, speaking from experience) to fully digest the material. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 02:33, 17 February 2009 (UTC)

== ANSI Standard PH2.7 ==

Hi Jeff,

I'm desperately trying to track down one of the references you cited:

ANSI PH2.7-1986. American National Standard for Photography — Photographic Exposure Guide. New York: American National Standards Institute.

If you can help me, could you contact me through my talk page, thank you very much.

Ronan
[[User:Ronomal|Ronomal]] ([[User talk:Ronomal|talk]]) 16:02, 18 June 2009 (UTC)

== Citations ==

I hadn't noticed that you had removed inline citations in a previous edit.  I agree they look nasty this way; it reminds of how much I prefer the use of footnote numbers.  [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 08:14, 27 December 2009 (UTC)

:I've commented on this on the article's talk page. For this particular case, I think we are better, for now anyway, without inline citations, regardless of format. Interesting that you use author-date in your paper ... ;-). [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]])

::Yes, we've been over that. [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 09:06, 27 December 2009 (UTC)

:::As I recall though, the issue then was the awkwardness of hand-coded <nowiki><a></nowiki> tags in the DOF article. It's not a factor in the [[Image circle]] article (and I don't think links are needed for an article that short). The biggest complaint about author-date is that it takes up too much space, though in this case that's arguably because I've cited more sources than needed for statements that aren't controversial. In any event, author-date is the standard for the natural sciences, including Ray 2002.

:::An alternative for the Image circle article would be to cite single sources and put the others as Further reading, though it's conventional not to give page numbers when that is done, making the reader's task much harder. Whatever WP policy, a source without a page number is for practical purposes unverifiable (given the choice, I'd usually rather have page numbers than inline citations without them). Again, I think for an article this short, we're fine (and perhaps better off) without inline citations. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 09:24, 27 December 2009 (UTC)

== Film Speed ==

Thanks for calling my correction a "rant".

"AIN'T" isn't proper English no matter how many billion times it is uttered, accepted in the vernacular or not.

If you want to change my hour's hard work and citations/explanations of speed back again, you'd better have something better than "Canon and Nikon" say so.  Kodak and Ilford have used the improper speeds too, BTW.  Just because an improper convention is used over and over again doesn't make it right.  And it *is* on.  If you want to just revert a well-thought-out correction without any explanation or time in justifying corrupted speed ratings, you're the one doing the reader harm, not me.  I at least LEFT the improper speeds.  You didn't do the proper numbers the same courtesy.  I have a race track photo from 1956 rated at 200,000 on my wall. . .  <small><span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:ISOGuru|ISOGuru]] ([[User talk:ISOGuru|talk]] • [[Special:Contributions/ISOGuru|contribs]]) 22:52, 11 January 2010 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->

:I don't doubt the effort involved, but you have provided no citations whatsoever, and have provided no explanations other than just stating your opinion. As I've mentioned, the progression you claim isn't illogical, but without support from a reliable source, you have no defensible basis for claiming that values are “improper”. Unless there is something about you we do not know, ''you'' are not a reliable source. Neither am I. If you read the WL'd article on verifiable sources, you will discover that any editor may remove any unsourced material at any time. Two of us have asked for sources, and you apparently feel no obligation to provide them. Accordingly, I removed the unsourced material.

:I called the “correction” a ''rant'' because of the manner in which it was made: injection of unsupported personal opinion, using square brackets rather than parentheses, using full caps for no reason, and needlessly repeating the same long, visually disrupting message several times rather than just providing a note. Perhaps I was a bit heavy handed. If it were simply a matter of style, I'd have moved the comments into a note, but absent a reliable source, I could not due so.

:If you believe a published value is “improper” but lack a source to support it, the place to propose it is on the talk page rather than defiantly changing the article.

:As for an ISO speed of 200,000, it's fine to add it if you can support it with a reliable source. You did not do so.

:It's probably reasonable to ask for a more specific citation than “Canon and Nikon”, at the very least citing brochures or other online information. I added the notes as an interim step; bear in mind that I wasn't the one who added the higher speeds, and that, prior to the notes, there was no sourcing whatsoever.

:Again, the rule for Wikipedia is that material added to an article must be supported by reliable, verifiable sources. This is especially true for material over which there is disagreement. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 23:41, 11 January 2010 (UTC)

:Very interesting that, one and a half years later, your committee finally accepted some very obvious arithmetic patterns and gave up some power of two nonsense.  Was the latter verifiable?  Or did it have something to do with a programmer's compulsion. . .
In any case, am glad to see digital cameras (and users) haven't been completely successful in rewriting photographic history.
Your heavy-handedness has precluded me from wasting any more of my time on these silly political threads.
But nice to see you finally got it right.  Heaven forbid someone not know the rules of writing Wikipedia articles try to contribute something that isn't available in Google Books!
Now I am off to process film, use my light meter with the 12,500 reading on it, and accelerate as much film as I want to.  It's amazing how many "experts" on here don't have access to similar income from their photographic endeavors.
~Former contributor ISOGuru  <span style="font-size: smaller;" class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/70.62.196.146|70.62.196.146]] ([[User talk:70.62.196.146|talk]]) 16:58, 22 November 2011 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->

== Use of ''Ansel Adams and Camera'' ==

In the article on [[Ansel Adams]], you recently replaced a non-free image with J. Malcolm Greany's ''Ansel Adams and Camera'' on the basis that the latter image is in the public domain. How did you determine that this image is a work of the U.S. government? [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad|talk]]) 22:50, 17 March 2010 (UTC)

: I obtained this particular image from a Yosemite National Park website, whis is a unit of the National Park Service, which is a subdivision of the U. S. Department of the Interior.  I listed the specific web page in the image file on Wikimedia.  The original photo caption reads "Ansel Adams shown as pictured in the 1950 Yosemite Field School yearbook and in “Yosemite Nature Notes” in January 1952."  I researched the photographer J. Malcolm Greany and learned that he worked for the U.S. Fish and Wildlife Service in Alaska, and had been on a trip with Ansel Adams near Juneau, Alaska, probably in 1947.  A similar photo from that trip, almost certainly taken during the same photo shoot, appears on a University of California - Berkeley website.  Adams is wearing what appears to be the same clothing, using the same camera, and what looks like the same hillside is behind him, though that photo was taken from a different angle.  This is the evidence I used to conclude that this Yosemite website image, which is probably 63 years old, is in the public domain.  Your feedback is welcomed.  [[User:Cullen328|Cullen328]] ([[User talk:Cullen328#top|talk]]) 03:12, 18 March 2010 (UTC)

::I've replied on [[Talk:Ansel Adams#Use  of "Ansel Adams and camera"|Talk:Ansel Adams]]. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 09:18, 18 March 2010 (UTC)

::: Thank you for the opportunity to learn a little bit more about image copyright issues.  I appreciate your knowledge and observations on this Ansel Adams portrait image. [[User:Cullen328|Cullen328]] ([[User talk:Cullen328|talk]]) 05:31, 19 March 2010 (UTC)

== Perspective control lenses ==

Hi there,

I'd made a brief remark in the comment when I'd added the advert tag, or at least I thought I did.  Re-reading the article, I'm not sure it's so much advert that is wrong with it, it's just far too much detail.  I kept reading yet another paragraph about another manufacturer's offering and thinking "so what?".  I wouldn't expect that under an article for say, prime or zoom lenses.  I know these are very speciailised bits of kit with an interesting history, but I only think that lenses of note should be described, with perhaps a link to the manufacturer page (on wikipedia) for the other players.  

Cheers, sorry I did'nt explain that at the time [[Special:Contributions/90.195.131.21|90.195.131.21]] ([[User talk:90.195.131.21|talk]]) 20:34, 26 March 2010 (UTC)

== Critique of Ansel Adams ==

Hello!  I've done an annotated critique of the Ansel Adams article, which I invite you to review at [[User:Cullen328/Sandbox Ansel Adams]].  My wife gave me a copy of the Alinder biography for my birthday, which I've just finished reading.  I am now prepared to make a lot of edits to the article, but will start out with various factual "nuggets" rather than a major rewrite.  I hope to hear your detailed thoughts on how the article can be improved, so that the process can be a collaboration among all interested editors.  [[User:Cullen328|Cullen328]] ([[User talk:Cullen328|talk]]) 21:55, 11 April 2010 (UTC)
: I admit that I do not yet understand the distinction bwteeen "references" and "notes" in the Ansel Adams article.  When I use the "cite" function on the editing toolbar, it creates a reference.  I have used this on many other articles without a problem. I guess that this article has so many references that some kind of "two-tiered" structure is called for.  I do not understand how to create these references or notes in an efficient way.  Maybe you can help enlighten me? [[User:Cullen328|Cullen328]] ([[User talk:Cullen328|talk]]) 00:46, 20 April 2010 (UTC)

==Arizona Law==

Ahh jeff we meet again, haha. You know i actually do like you, you do a good job around here. Ok you got rid of my article. You know more about wikipedia then I do. How can I include it properly? [[Special:Contributions/67.246.175.103|67.246.175.103]] ([[User talk:67.246.175.103|talk]])  <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|undated]] comment added 20:51, 9 May 2010 (UTC).</span><!--Template:Undated--> <!--Autosigned by SineBot-->

:You do yourself a disservice and hurt your credibility (at least with respect to NPOV) with a title like you added above. Be assured that I make no comment on the law, but simply on what's appropriate for Wikipedia.

:We don't include the complete text of outside articles for at least two reasons:

:# Wikipedia is a summary of information rather than a repository. When long blocks of text are included in an article, the reader is forced to read through the entire mess, and the key points may be lost. That's why we summarize.
:# [[Fair use]] allows brief citations of other sources, but including complete articles clearly violates copyright.

:How to include something? Summarize a key point or two, realizing that it's impossible to reasonably include everything that's ever been said about a topic. Also bear in mind that there's a difference between someone like Obama or Schumer and a that may not even meet [[WP:RS]]. And again, we need to be careful to maintain an overall balance that's representative of all sources on a topic.

:A comment on spelling, grammar, and reference formatting. Although Wikipedia generally treads quite lightly on such errors, at some point it becomes a bit unfair to continually impose the burden of cleanup on others, so any effort to reduce that burden is appreciated. Perhaps you could look at a couple of the citations that I just fixed for some idea how to do it. The most basic requirement is to enclose each citation in <code><nowiki><ref></nowiki></code> ... <code><nowiki></ref></nowiki></code> tags; the key information to provide is the source (e.g., URL), title, author, date, and publisher. I agree that the citation templates are difficult to use for one unfamiliar to them (and perhaps to many who ''are'' familiar with them). Providing the basic information as it might normally be written (without the templates) makes cleanup a lot easier; the arrangement need not be perfect, though the more it resembles the displayed appearance of the other references, the better the article looks before someone cleans up a citation. Rearranging material is a lot easier than having to go to the source to retrieve it. As I mentioned, titles need to be given as they appear in the source, without paraphrasing.

:Also, please sign your comments on Talk pages (but not your article edits) with four tildes (<nowiki>~~~~</nowiki>) as indicated below the edit box. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 21:34, 9 May 2010 (UTC)

::Sorry the title was more of a joke. I have been working on mastering the format stuff but its going slowly, sorry about that. Ok how is this for a first draft for that article

<blockquote>
For critics that believe that the law is racially biased they have pointed out other perceived bills that have been introduced in the same time period. These bills were considered by them to be anti-Hispanic (insert source from article).
</blockquote>

Is that NPOV? Sorry if i pissed you off it was intended. [[Special:Contributions/67.246.175.103|67.246.175.103]] ([[User talk:67.246.175.103|talk]]) 22:03, 9 May 2010 (UTC)

:The source is secondary and possibly not [[WP:RS]]; the ''Wall Street Journal'' should be cited directly, and an indisputably more NPOV source (perhaps such as [http://www.fox11az.com/home/Students-protest-bill-that-would-ban-ethnic-studies-93081864.html this report] on [[Fox News]] or [http://www.azcentral.com/arizonarepublic/viewpoints/articles/2010/05/09/20100509ethnic-studies-bullies-tucson.html this op-ed] in the ''[[Arizona Republic]]'') found for HB&nbsp;2281. But I'm hardly the steward of this article; we need consensus among the various editors, and accordingly, the discussion belongs on the article's Talk page. I will not further address it here.

:Actually, I wasn't “pissed off”, but as for your statement “Sorry if i pissed you off it was intended”: it's hard to tell whether you're joking, but a statement like this is a good way to get blocked. You don't want to go there.

:Again, continue this on the article's Talk page. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 22:44, 9 May 2010 (UTC)

::Huh? I was seriously apologizing. You just seemed mad and that wasnt my intention [[Special:Contributions/67.246.175.103|67.246.175.103]] ([[User talk:67.246.175.103|talk]]) 01:04, 10 May 2010 (UTC)

:::So you meant, “Sorry if i pissed you off it ''wasn't'' intended”. But that isn't what you said ... In any event, there's no need for apology, because no offense was taken. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 01:27, 10 May 2010 (UTC)

::::That might be the single worst spelling error I have ever made. Dang. [[Special:Contributions/67.246.175.103|67.246.175.103]] ([[User talk:67.246.175.103|talk]]) 15:42, 10 May 2010 (UTC)

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{| style="border: 1px solid gray; background-color: #fdffe7;"
|rowspan="2" valign="top" | <!--[[File:Civility Barnstar Hires.png|100px]]-->[[Image:Civility barnstar.png|100px]]

|rowspan="2" |
|style="font-size: x-large; padding: 0; vertical-align: bottom; height: 1.1em;" | '''Civility Award'''
|-
|style="vertical-align: middle; border-top: 1px solid gray;" | I was looking for a "patience"-barnstar. Doesn't seem to exist. I guess you know what this is for. [[User:Seb az86556|Choyoołʼįįhí:Seb az86556]] <sup>[[User_talk:Seb_az86556|> haneʼ]]</sup> 03:59, 18 July 2010 (UTC)
|}

== Air Mass chart ==

[Moved from user page]

Can you add the young 1994 and pickering 2002 charts as well. <nowiki>[</nowiki>[[User:MySchizoBuddy]]]

== Air Mass for zenith angles greater than 90deg ==
If you are at 1km above sealevel. your zenith angle at horizon will be greater than 90deg. Do any of these models work correctly for more than 90deg angles. 
Plus can you share your excel spreadsheet --[[User:MySchizoBuddy|MySchizoBuddy]] ([[User talk:MySchizoBuddy|talk]]) 08:28, 9 October 2010 (UTC)

:[General answer moved to [[Talk:Airmass#Zenith greater than 90deg|Talk:Airmass]]]

:I can send you my spreadsheet if you tell me where to send it. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 11:17, 9 October 2010 (UTC)
can you send it to myschizobuddy@gmail.com. I will remove this email once you send me the file. thank you  <small><span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:MySchizoBuddy|MySchizoBuddy]] ([[User talk:MySchizoBuddy|talk]] • [[Special:Contributions/MySchizoBuddy|contribs]]) 20:03, 11 October 2010 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->

== Postman always rings twice ==

{{YGM}}

== like how you break things down ==

Like how you disaggregate and discuss things, logically.  Very fun to read.[[User:TCO|TCO]] ([[User talk:TCO|talk]]) 15:31, 15 December 2010 (UTC)

== Air Mass == 

Hello Jeff... I found a graph of yours relating how different papers calculate AirMass. I'm working on an algorithm that uses Airmass as one of the inputs into a solar energy performance calculation. The algorithm gets buggy as the zenith angle approaches 90. The Airmass calculation is part of the problem. I'm using the following formula:

AM = 1 / (Cos(Zenith) + 0.5057 * (96.08 - ZenithD) ^ -1.634)    

But I could also use the Kasten & Young...

AM = 1 / (Cos(Zenith) + 0.15 * ((93.885 - ZenithD) ^ -1.253))      

It occurs to me... The Kasten & Young calculation will have the same problem... I could use the Hardie calculation though? I was going to ask you if you had a suggestion but I'm just going to try the Hardie calculation. It keeps the AirMass value down at higher zenith angles. Thanks for putting that graph together. Best [[User:Mrshaba|Mrshaba]] ([[User talk:Mrshaba|talk]]) 21:21, 16 December 2010 (UTC)

(Reply is on user Talk page) [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 01:29, 17 December 2010 (UTC)

:Thanks for the follow up Jeff. The specific algorithm I'm working with has an airmass value inserted into a polynomial expression. This expression stays positive until you reach airmass values of about 16. Past 16 you start getting negative values that don't make any sense. The zenith range I'm working with stops at 87.5 degrees so I was thinking that Hardie's equation would work for me since it doesn't go over 16 and the errors stay reasonable up to zenith angles of 87.5 degrees. When you are simulating solar power system performance these high zenith values represent but a small fraction of total output so there is little need for precision. Ultimately, I kept the first AM formula I listed above but put an IF/Then statement into the code that kept the AM values from going over 16. Seems to work. It's good to know there are alternative airmass expressions though. Ciao [[User:Mrshaba|Mrshaba]] ([[User talk:Mrshaba|talk]]) 14:46, 17 December 2010 (UTC)

{{talkback|Wasted Time R|Arizona SB1070|ts=03:04, 24 April 2011 (UTC)}}

== Compromise? ==

Jeff, as a fan of good punctuation, can you nevertheless support the compromise to put an end to the hassles, at [[WT:MOS#RfC:_simple_resolution_to_disagreements_over_dashes]]?  [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 03:35, 8 May 2011 (UTC)

==Thanks==
Hello J. Thanks for your note. Things can get confusing when you get someone who is edit warring the way that editor was and edit summaries have a limited amount of room and its difficult to leave a full explanation of what one is doing. I appreciate the time that you took to explain things on my talk page. Cheers and have a great weekend. [[User:MarnetteD|MarnetteD]] | [[User talk:MarnetteD|Talk]] 13:57, 24 June 2011 (UTC)

== Your [[WP:GA|GA]] nomination of [[Arizona SB 1070]]==

Hello, I just wanted to introduce myself and let you know I am glad to be reviewing the article [[Arizona SB 1070]] you nominated for [[WP:GA|GA]]-status according to the [[WP:WIAGA|criteria]]. [[Image:Time2wait.svg|20px]] This process may take up to 7 days. Feel free to contact me with any questions or comments you might have during this period. &ndash; [[User:Quadell|Quadell]] <sup>([[User_talk:Quadell|talk]])</sup> 13:43, 21 July 2011 (UTC)

:P.S. because there are so many nominators, I request that any communication be centralized at either [[Talk:Arizona SB 1070/GA1]] (when it applies to the review) or my own talk page (when it's about me specifically). Thanks! &ndash; [[User:Quadell|Quadell]] <sup>([[User_talk:Quadell|talk]])</sup> 14:29, 21 July 2011 (UTC)

:Notice: I have reviewed the article and placed it {{onhold}} until issues are addressed. All the best, &ndash; [[User:Quadell|Quadell]] <sup>([[User_talk:Quadell|talk]])</sup> 20:26, 21 July 2011 (UTC)

The article [[Arizona SB 1070]] you nominated as a [[Wikipedia:Good article nominations|good article]] has failed [[Image:Symbol unsupport vote.svg|20px]]; see [[Talk:Arizona SB 1070]] for reasons why the nomination failed. If or when these points have been taken care of, you may apply for a new nomination of said article. All the best, &ndash; [[User:Quadell|Quadell]] <sup>([[User_talk:Quadell|talk]])</sup> 12:43, 29 July 2011 (UTC)

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== Atmospheric refraction ==
Jeff, I have enjoyed reading some of your writings on atmospheric refraction, or R, near the horizon. R here is the angle (usually reported as 34 arc minutes) below the horizon that a star (besides the Sun) just becomes visible.  However I do find the integral equations you develop somewhat confusing.  More on that later.

  In addition, the R estimates are of interest.  I think that the almanac authors have assumed an average value of elevation at sunrise or sunset of

                Elevation = -(R + 16) = -50 arcminutes  ... below the horizon

(with 16 arcminutes the approximate semidiameter of the Sun) to construct their tables of sunrise and sunset times.  They never admit to this, or give any hint to their models. 
:A fair number of almanacs and similar productions actually do, if you look hard enough. The value of −50 arcminutes almost always used, because for “average” values for rise and set times, there really isn’t a good alternative. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 01:22, 21 May 2016 (UTC)

  I find much of what I read confusing about the viewing effect of atmospheric refraction, but your statements make sense, thank you.  The problem I'd like to address is how much the variation in R will affect sunrise and sunset times estimates. I've read that it might be 4 to 5 minutes.

Leo  <small class="autosigned">—&nbsp;Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/2605:E000:7F0E:BF00:4A0:245:BEFB:A7F7|2605:E000:7F0E:BF00:4A0:245:BEFB:A7F7]] ([[User talk:2605:E000:7F0E:BF00:4A0:245:BEFB:A7F7|talk]]) 20:51, 19 May 2016 (UTC)</small><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->

:Time and chance happeneth with them all, but I think 4–5 minutes is on the high side. Schaefer and Liller (1990) reported that the times could only be predicted to about 4 minutes, but their conditions were fairly extreme, involving several observatories at significant elevations, where the light path was considerably longer than for rise or set at a level horizon. Jean Meeus, the US Naval Observatory, and others suggest that prediction to an accuracy of a minute is reasonable. On any given day, of course, almost anything can happen. The more elaborate models (e.g., Garfikel 1967) rely on atmospheric parameters that are almost never known, so even then, extremely precise predctions are almost impossible.
:More significant in most cases is the occlusion of the horizon by natural or man-made terrestrial features. It’s possible to adjust for changes in refraction and parallax with altitude (and as the altitude increases, the refraction is less, so the variation usually decreases), but few applications bother; [http://www.largeformatphotography.info/sunmooncalc/ I do it], and [http://ssd.jpl.nasa.gov/horizons.cgi JPL Horizons] can adjust to the nearest minute. Applications such as [http://photoephemeris.com The Photographer’s Ephemeris] and [http://www.photopills.com/ PhotoPills] essentially offer the same capability via searches. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 01:22, 21 May 2016 (UTC)

== Welcome back ==

Jeff, we've missed you.  [[User:Dicklyon|Dicklyon]] ([[User talk:Dicklyon|talk]]) 05:25, 20 November 2016 (UTC)
:Dick, I think it’s just a visit. I noticed a couple of things that I could have done better, and felt obliged to clean them up. [[User:JeffConrad|JeffConrad]] ([[User talk:JeffConrad#top|talk]]) 07:06, 20 November 2016 (UTC)

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== References for "Focus Stacking" ==

Hello, I intend to improve the "Focus Stacking" wikipedia article and noticed that you added references on 27 July 2009 for Johnson 2008 Pg 336 ("How to do Everything: Digital Camera"), and Ray 2002 Pgs 231-232 ("Applied Photographic Optics"). I've been unable to view the relevant pages online or in print. Could you please tell me, if you recall, in what context the term "focus stacking" was used in those references and what relevant references were used by those books?

Thank you for your help.<br>
[[User:NewageEd|NewageEd]] ([[User talk:NewageEd|talk]]) 16:55, 2 July 2019 (UTC)