Talk:Exposure value

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Exposure value sounds right (I don't know for sure), but Canon calls it evaluation value in the explanation for Exposure Compensation.

Contents

[edit] Light gathered

In trying to understand all the values, I must admit Im a bit confused now. The F-Number article tells that the higher the number, the smaller the hole the light comes through. That makes sense (given the numbers f/8 for bright and f/2 for dark of the human eye). Now Table1 in this article says for e.g. f/8 the EV at 60s is 0 and at 1/8000 second is 19. So taking this table only, the lower the EV, the more light has been gathered (same aperture + longer exposure makes more light in total). But then I totally do not understand Table2. shouldn't it show the light amount gathered vs EV? So following that Table, the higher the EV, the more light will be gathered, contrary to what I got and explained from the other parts. Could anyone clear this up? especially in the article?

Table 2 explains what a meter does. Luminance is how much light is coming from the scene; when it's low, you need a slower shutter or lower f-number, hence a lower EV, to properly expose a photo. Dicklyon 15:56, 18 August 2006 (UTC)

[edit] Link to C.R.I.S.

I restored the link to C.R.I.S. Under “kyoritsu test equipment,” the links for the Multi Camera Testers (e.g., EF-1) make reference to EV and K, and the links for Calibrated Light Sources (e.g., LBF-2000) make reference to LV at ISO 100 and K. The link is included to support comments in the text.

I also made slight changes to section headings for consistency with the text ... which I forgot to note in the edit summaries.

JeffConrad 22:00, 19 August 2006 (UTC)

Jeff, thanks for that explanation. I won't delete it again, but would suggest we put a little explanation by the link, and maybe link deeper if possible to the relevant pages. I found nothing on a quick first look there. Dicklyon 22:07, 19 August 2006 (UTC)
The Flash makes it hard, but you can google up some URLs to use instead: [1] and [2] (both are in criscam's "old" section; someone needs to explain to them about URLs so they won't rely on the just the flash carp. Dicklyon 22:12, 19 August 2006 (UTC)
Dick, I'm hesitant to link to an "old" page for fear that it might vanish. Does the comment that I added at least partially address your concern? JeffConrad 05:37, 23 August 2006 (UTC)
Partially. But don't be surprised if someone comes along and deletes it as link spam. Dicklyon 05:57, 23 August 2006 (UTC)
Dick, see if the 24 August 2006 edit helps. If so, I'll make the same change in the Light value article (I need to fix "C.R.I.S.S." anyway). JeffConrad 02:03, 24 August 2006 (UTC)
I like that much better. Dicklyon 02:12, 24 August 2006 (UTC)

[edit] Edits of 7–18 October 2006

A long discussion with Marc Lacoste has raised several issues about the style of this article (and by implication, similar articles on photographic terms). Some of the issues probably apply to Wiki articles in general, but because a few are a bit esoteric, this may be the place to start.

The current version includes a combination of Marc's and my recent edits; if the format seems reasonable, perhaps it should be incorporated into similar articles. It does involve some effort, however, so if people don't like it, I'd rather not bother.

[edit] Citation of National and International Standards as Sources

The authoritative sources for several of the photographic term articles are national and international standards, such as from ANSI/ASA and ISO. Such references are comparatively uncommon, and are given little coverage in most style guidelines. As nearly as I can tell, they are not covered at all in the Wikipedia Manual of Style ("WMoS"). With author-date ("Harvard") referencing, the Chicago Manual of Style, 15th ed., ("CMS") would use citations such as (ISO 1974) or ISO (1974), depending on context. Nearly universal practice within organizations that publish such standards is a style such as (ISO 2720:1974) or ISO 2720:1974, and this style also appears to be common in the photographic literature (see, for example, Ray (2000 305–309), listed in the References fo the Exposure value article; the chapter I mention here actually was written by Ralph Jacobson). This form also seems to find use in Wiki articles; see, for example ISO 31. I prefer this form, which I have used in several of the photographic-term articles on which I recently have worked; it would seem to provide everything that strict CMS style offers, with the additional benefit of the specific reference for those who may be familiar with it.

[edit] Citation of Self-Published Material as Sources

I have avoided citation of self-published articles by Doug Kerr, Gordon McKinney, and me as References, because Wiki guidelines expressly forbid it. Although I agree with Marc's contention that Extenal links tend to collect all manner of garbage, I'd rather adhere to the Wiki guidelines because I am afraid that, once the door is opened to self-published material as sources, there will be no such thing as a reliable source. I'd rather we monitor external links and remove obvious link spam.

Jeff, I think there's a different standard for sources versus external links. I agree that self-published materials as sources is seldom OK (the guidelines don't say it's forbidden, though); there are some gray cases, though, such as David Jacobson's Lens FAQ; it's self-published (I think), but has been through some years of use, review, and revision, so it's pretty reliable. I think some of your stuff, and Doug's, are as good, but have not been subject to that kind of community exposure and feedback, so are not as good as sources. Nonetheless, they don't have to pass as high as standard to be used as external links. If they are non-commercial credible opinions or analyses related to the article topic, that's usually enough. Of course, you should hesitate to link your own papers. But if you choose to link some others, I'm going to add some of yours. Dicklyon 02:14, 13 October 2006 (UTC)
I think we agree; I like to think that I hold external links to a fairly high standard, even if it less than the guidelines for a reliable source. There may indeed be a few exceptions, such as Jacobson's FAQ, which for many is still the gold standard of introductory treatments of the subject, and possibly Merklinger's The INs and OUTs of FOCUS, which has been around for a while and has been extensively quoted. Nonetheless, I don't think either has the same status as works by Ray, Stroebel, or Zakia, and I would cite either as firmly establishing a position only reluctantly—how does one make the call on which self-published materials are reliable? If Jacobson, why not Atkins, Koren, or Rockwell (or even Conrad or Lyon)? There is a lot of nonsense on photo-related web sites, and once the bar is lowered, it may be impossible to prevent free fall.
Perhaps I'm shameless, but I'm not above linking to one of my papers (I'm sure not the only one to do such a thing), especially if it explains a point in more detail than may be appropriate for a Wiki article. JeffConrad 09:36, 13 October 2006 (UTC)
I hear you. Sometimes those Lyon papers are just what we need! Dicklyon 15:01, 13 October 2006 (UTC)
Let's put it this way: there are many far less appropriate links. It's the reader's choice to follow or not follow an external link, especially when it is not represented as authority; if the link to a potentially useful site or article is omitted, the reader does not have the choice. The key, I think, is the exercise of reasonable judgment when including links. When no endorsement is implied, the call isn't as critical. JeffConrad 23:17, 13 October 2006 (UTC)

[edit] Mathematics as Intimidating for Some Readers

The definition of exposure value is imprecise without the math, but precision may not be necessary for all readers, and may be offputting. I'm inclined to put the formal definition in a separate section; would this suffice to keep the article accessible?

Jeff, to tell the truth, I am not keen on the math the way it is now. I preferred what I had back in June, which started off with just EV = AV + TV and then the (logarithmic) definitions of TV and AV based on exposure time and aperture. I do appreciate the logic of your approach, but it's a lot more complicated. It brings issues of light meter calibration, photometry, and sensitometry right to the front, and defers the definition of EV to pretty deep in the intro, and involves squares and divisions with too many symbols for a naive user to get their head around. So, my suggestion would be to make a new section for all that stuff, and to put EV = AV + TV and not much else in the intro. This is the simplest valid definition, right? The rest is more about how to choose a good EV. Dicklyon 02:22, 13 October 2006 (UTC)
Isn't the simple (and hopefully intuitive) definition given in the article's opening sentence? The problem I see with with introducing AV and TV is that we dabble in APEX, a concept that essentially was stillborn. For practical purposes, AV and TV are superfluous except as historical footnotes. Having said that, perhaps the intial definition could deal only with the left-hand side of the exposure equation, with the more complete definition moved to an advanced section. Perhaps the APEX reference also should be moved to the advanced section. I wonder if squares and division are any more intimidating than logarithms (which still give me trouble ...). It sounds as if some simplification is indicated, however. Would putting the math in a section separate from that with the two images (with which it doesn't really belong) be a start? Perhaps the EV vs. camera setting table could be introduced before the math and without any reference to it. To my mind, the mathematical definitions and the relationship to luminance and illuminance are somewhat advanced topics that really aren't needed by most practical photographers.
On choosing a good EV: one must of course know the proper EV, either from a meter reading or from another source, such as a table. I added a link to Fred Parker's EV table, but Marc suggested that Wikipedia should contain such a table directly. Perhaps this article is the proper place for it? JeffConrad 05:25, 13 October 2006 (UTC)
I agree that choosing a good EV is important, and your expert knowledge of that metering topic is appreciated. But to me, the definition of EV is just TV + AV, and you can't really talk about it without knowing a bit of that APEX stuff. The logs can be intimidating, it's true, so maybe small 1D tables to define AV and TV would be a way around that.
I would argue that the definition of EV is
\mathrm {EV} = \log_2 \frac {N^2} t,
which doesn't require mention of AV or TV. I'm working on a version that goes no further than this in the introduction. As nearly as I can tell, the concept of EV predated APEX by several years (some Hasselblad lenses had EV markings around 1957, while APEX was not proposed until 1960), so we should be able to handle the definition without mentioning AV or TV. I wish we could find a reader from Germany who was an actual witness (and can provide reliable sources, of course ;-) ). JeffConrad 06:30, 13 October 2006 (UTC)
Really? It had not occurred to me that EV could pre-date APEX. Anyway, that definition is OK, but it's going to scare some people. I thought using APEX was a way to make it much more accessible, but maybe I'm out of order. Dicklyon 06:48, 13 October 2006 (UTC)
I'm relying on comments in the forward to ASA PH2.5-1960 (long unavailable, unfortunately). As nearly as I can tell, the idea of EV was to simplify choosing among combinations of camera settings that would give the same exposure; the APEX proposal extended the concept, stating "There appears to be merit in the proposition that the exposure value concept be extended to include all the parameters of the camera exposure equation."
Some people are scared by any math, but I don't think my definition is any more intimidating than yours of 29 June 2006. In any event, I don't know how to simplify mine any further. JeffConrad 07:15, 13 October 2006 (UTC)

[edit] Table of Exposure value vs. Camera Settings

I extended the EV vs. camera settings table to EV −4 to cover the light froma full Moon; it could be argued that I should have gone to EV −6. The logarithmic EV scale was not chosen without reason; when linear sequences are used, some of the values can be come quite large, such as the exposure time for EV −4 at f/64. Accordingly, I expressed exposure times longer than 60 seconds in minutes, and appended the symbol 'm' to those values to so indicate. Apparently the meaning of the 'm' in this context isn't clear to everyone, even with a note in the table captions. The official SI abbreviation is 'min'; it's easy enough to use it, though the presentation of the data becomes less attractive. Alternatively, the really long exposure times simply could be eliminated, as I have done with really short exposure times less than 1/8000 seconds.

JeffConrad 01:57, 13 October 2006 (UTC)

I think the fix here is just to put the "m" note by the table, not in a footnote. Jeff, thanks for all your hard work and serious attention on this article. It has benefitted enormously from your work (even if I don't like your mathiness up front so much). Dicklyon 02:26, 13 October 2006 (UTC)
This sounds simple enough (Marc had the same suggestion); it also follows style convention for tables. With the note that close, it probably doesn't need to be clickable, though that's not difficult if it's needed. The question now is the footnote style ... conventionally, notes for table data cells are alphabetical, though I'm not sure that applies to table captions. I don't think a superscripted number is a good idea because we already have a numerical series of notes. Perhaps an asterisk is the solution ... I'd first like to see if there are any other comments, though. As Marc pointed out, we 'Merkins sometimes forget that what is intutive to a native-English speaker is not so for others.
As noted in my comment in the earlier section, it sounds as if the math needs some rework. JeffConrad 05:21, 13 October 2006 (UTC)

[edit] Edits of 14–15 October 2006

Dick, I left AV and TV out of the definition, in trying to cut the math to the absolute minimum. Put them in if you insist, but I still think they are irrelevant to this article (and they are well covered in the APEX article). The EV concept indeed was introduced to simplify setting camera controls, but without logarithmic markings on the camera controls, AV and TV are of no value. Presumably, when EV was introduced, the photographer would obtain the EV from a meter or tabulated exposure guide, and transfer that value to the guide. To the extent of my knowledge, the first use of EV was on Hasselbald lenses: one would depress the EV-lock button to change the EV, and then release it. The shutter time then would change with the f-number to maintain constant EV. There was no mention of AV or TV—the shutter and aperture markings were arithmetic. I don't think I've ever seen tables of AV and TV outside of obsolete ANSI standards and perhaps a photo book or two (I guess the Minolta Flashmeter III did specify f-number indication range in AV).

Well, I still don't see how you can omit EV = TV + AV in the section on EV and APEX. The whole section uses the complicated multiplication, squaring, division, log type math instead of the additive math from the system that it's talking about. Personally, I think APEX is useful and easy to understand, and even though it didn't catch on it's worth demonstrating a bit. Dicklyon 00:41, 15 October 2006 (UTC)
It depends on how complete this section needs to be. I tried to keep it to an absolute minimum, showing only how EV could be used as a measure of luminance or illuminance (necessary because nearly every equipment manufacturer uses EV in that sense). In particular, I had hoped to avoid essentially a complete duplication of the APEX system article, which covers the subject in depth. If people think it important, I can include some of the material from that article, but I'm always concerned about maintaining consistency in essentially parallel articles. Perhaps I also need to make it clear that EV as an indicator of luminance or illuminance is the only element of APEX that has survived. JeffConrad 02:03, 15 October 2006 (UTC)
Dick, I've added a one-sentence summary of the purpose of APEX, as well as a direction of the reader to that article. Does this help? JeffConrad 02:53, 15 October 2006 (UTC)
Dick, one other minor point that I missed last time: in light of the last sentence of the first paragraph in the article, isn't the sentence, "Each such increment is known as a change of one "stop" or one "step" in exposure" in the Formal definition section redundant? JeffConrad 09:49, 15 October 2006 (UTC)
Redundant, yes, a bit. However, I think having it there will be very helpful to people who don't fully appreciate that that's what the log2 implies. These are the people who won't remember from the lead paragraph a line that would help them interpret the definition. Dicklyon 16:39, 15 October 2006 (UTC)
I still think the inclusion of the APEX values is superfluous. We now define EV in terms of two other terms that we haven't defined, I don't know how that can be done. I also question use of "definition"; ASA PH2.5-1960 said, "The equation then takes the form ..." I also question the statement, "proper exposure value can be computed from a film speed and a light meter reading by EV = SV + BV"; I've never seen a meter that indicated in terms of APEX BV (I changed the acronym to LV for consistency with the rest of the article). Even the ANSI exposure guides don't list the values in the form indicated by APEX BV or IV (but that's another issue for another time and place ...) Also, why would we include BV/LV but not IV? I won't beat this to death, but I think we open a can of worms by mentioning the APEX stuff here. I don't see how the APEX values for the RHS quantities can possibly help the reader determine or understand exposure. If the material does remain, it think some rearrangement is indicated so that the details develop in sequence (unfortunately, that also would require some additional math). I also wish we could be consistent in the use of "stop" (the popular expression) and "step" (the formally correct expression, preferred by most of the ISO standards). JeffConrad 21:49, 15 October 2006 (UTC)
I've made a slight rearragement (we need the exposure equation before we can refer to it), trying to keep mention of the APEX stuff to an absolute minumum. I still don't think this material adds anything, but if you think it's needed, I won't bring it up again. One little issue that we get into by going back in time the conflict between current and previous standard letter symbols (e.g., L vs. B). We also are using acronyms vs. the quantity symbols that APEX employed. JeffConrad 22:23, 15 October 2006 (UTC)

I reformatted the tables using inline styles; the coding is cluttered and ugly, but I don't know of a good alternative except for adding several new table styles to the Common CSS, which I doubt would amuse anyone.

I'm working on a table of exposure values based on the withdrawn ANSI exposure guides PH2.7-1973 and PH2.7-1986, and I hope to have it done in a day or two. Other sources, such as Kodak film data, have minimal data and several inconsistencies. The ANSI subcommittees that developed these guides were chaired by H.R. Condit and Leslie Stroebel, respectively, so they should be authoritative. Whatever I come up with will be an extreme simplification (the ANSI guides are 64 pages and 80 pages). I have some concerns about this, but most other tables, including the two in the external links, make similar simplifications.

I'm not sure that such a table belongs here, but I don't know where else to put it. It certainly doesn't belong in Light value. The more I look into this the more I am convinced that Light value, luminance value, incident-light value, or whatever are simply elaborately disguised forms of EV (when incident-light value is given for night scenes that consist primarily of light sources, one suspects that the values given do not derive from fundamental laws of physics). JeffConrad 22:40, 14 October 2006 (UTC)

I've added the table, for what it's worth. The location in the article probably is debatable, but I've assumed that a reader is primarily interested in using EV to set the proper exposure, and have tried to provide the necessary information for that first, with the stuff that is more of academic interest later. Considerably more subjects could have been included in the table, but the article already is getting quite long; hopefully, I have included situations of the most interest. JeffConrad 09:49, 15 October 2006 (UTC)

On second thought, I wonder if including the Further reading section listing Kodak Existing-Light Photography book is appropriate for this article. It contains a wealth of information about determining exposures for low-light situations, but this really isn't an article about exposure determination. Perhaps an article on that topic would be the appropriate repository for the tabulated exposure values as well existing-light data. JeffConrad 21:49, 15 October 2006 (UTC)

[edit] Edits of 18–19 October 2006

I made a preliminary attempt to eliminate redundancy in some of the articles on photographic terms. Much of the material on exposure meter calibration was removed, referring the reader to the Light meter article. At the time the material originally was added to this article, it was not included in the Light meter article; now it is redundant here. At Dick Lyon's request, some of the APEX material was restored, and a specific referral to that article (which now is more comprehensive than it was when that article was written.

This article still is a bit long; in particular, I'm not sure that the exposure guide ("Tabulated exposure values") really belongs here. Moreover, I think the link to Doug Kerr's APEX article is redundant (it's also in the APEX article). For some reason, we tend to mention APEX the minute exposure value comes up; the reality is that, while exposure value continues in common use, APEX. whatever its merits, was a concept proposed 45 years ago that never caught on. Had exposure mmeters been added to cameras just a few years earlier than they were, APEX never would have been proposed. JeffConrad 01:59, 19 October 2006 (UTC)

It's a big improvement. Still too long, maybe; I wouldn't object to more trimming. By the way, spurred by your comment I reviewed the APEX article, and made a few edits to the section about EXIF. Take a look. And I completely removed this bit that didn't fit with EXIF, so see if you think it needs to go back into some other section (sorry, looks like I truncated it some place):

The relationship between Iv and illuminance similarly depends on the speed scaling constant N and the incident-light meter calibration constant C:

I = NC2^{I_v}

ASA PH2.12-1961 recommended a value for C of 20.8 ± 5. Using the nominal value, an Iv of 0 was equivalent to 6.18 footcandles. Comparison with the recommendations in ISO 2720:1974 suggest that this value of C applied to a cosine-responding (flat) sensor rather a cardioid-responding (hemispherical) sensor, but unfortunately, ASA PH2.12-1961 made no mention

My point being that APEX is alive and well in EXIF, if not exactly in full original form. Dicklyon 05:36, 19 October 2006 (UTC)

It's alive, after a fashion (I originally added the EXIF material); whether it's well remains to be seen. See my latest edit of the APEX article—there is a bit of a conflict. I cannot see a home for the deleted material, so I've left it out.
My edit also finds yet another awkward example of reference to standards. In this case, everyone knows the standard as EXIF 2.2, yet the official designation is JEITA CP-3451, which I doubt anyone but the developers would recognize. The first citation that I used (JEITA 2002) is the way The Chicago Manual of Style would do it; I personally find it a bit awkward though. JeffConrad 09:52, 19 October 2006 (UTC)

[edit] Tables and Formulas

I like having the formulas in this article, but I'm somewhat confused about the relationship between the tables and formulas.

It is stated that the EV in Table 2 is with reference to ISO 100, and that formulas are provided for conversion to different ISO values. Shouldn't the EV in Table 2 remain consistent regardless of what ISO one is using in their camera? For example: If the full moon has an EV = 15 (as per Table 2) shouldn't it always have this same value since it's supposed to represent the actual amount of light present? Maybe I'm misunderstanding EV, as I'm thinking that it's an absolute value, but perhaps it's actually a relative value?

I was expecting Table 1 to be referenced to ISO 100 instead, and that the formulas can be applied to correct for various ISO as required. Meaning if one wants to photograph a scene that has an EV = 12 using ISO 100, one would use the f/ and shutter speed as per Table 1, but if one wants to photograph this same scene using ISO 200, one would have to correct using the ISO formula(s)?

My confusion arose when I used these same formulas to create similar tables specific for my camera, but the numeric results didn't make sense to me, hence my confusion. Can someone clarify this for me?

--Dennis Lee 18:52, 12 November 2006 (UTC)

You need to re-read the article. EV is an indication of a combination of f-stop and shutter speed; not a measure of light level. To use it to refer to a light level, you need to add an assumed ISO speed and an assumed meter calibration. At other ISO speeds, different f-number and shutter speed will be required to give a correct exposure. Dicklyon 20:07, 12 November 2006 (UTC)
I think I understand now, I was confusing EV with LV (Light Value). Thanks. --Dennis Lee 23:18, 12 November 2006 (UTC)
Light value is an even more confusing topic, since it has no standard definition. Dicklyon 00:13, 13 November 2006 (UTC)


I'm not sure if this is the right place, but I think currently the correction for higher ISO values in the formula is incorrect. It says: log(N^2/t)+log(S/100) = EV(S), but I think the correct one is: log(N^2/t)+log(100/S), because when rewriting this to have t=100*N^2/S*EV(S) makes t inverse to S, which is more like reality (EV=1 at ISO=1600 will be effectively the same as EV=5). --SimonOosthoek

You have misinterpreted. It says the exposure you should use should satisfy EV(100)+log(S/100) = log(N^2/t). Here, S is inverse with t as you require. I think you'll find that to be consistent with the examples. Dicklyon 21:37, 21 June 2007 (UTC)
Thanks for the clarification, I see where I misinterpreted --SimonOosthoek
It almost sounds as if we should mention, once again, that a greater EV indicates less exposure. This behavior seems to confuse a great number of people. JeffConrad 06:35, 23 June 2007 (UTC)

[edit] Exposure Value Chart

===EV Graph===
Exposure Value Chart
Exposure Value Chart

Lazaro Gimena, it is generally considered a bit of a WP:COI or WP:OR to publish your own original creations in wikipedia this way. I move it here, so other editors can consider it. If someone finds it to be useful, gets you fix the errors, and wants to include it in the article, we can consider that then. Please do not put it back yourself. Dicklyon 03:42, 9 February 2007 (UTC)

I tend to agree with Dick. To me, this seems to present the concept of exposure value as more novel than it is; the concept has been around for almost 50 years, though I'll concede that in recent years, the average photographer's familiarity with the basics is not what it once was. I cannot see how over- and under-exposure as shown in the graph relates to the rest of the graph. Perhaps I miss something, but I don't think this graph contributes anything that isn't already covered in the article. To my mind, the extra ornaments tend to distract rather than elucidate.
This graph implies the more traditional table of EV presented as f-number vs. shutter time. The article had such a table until the edit of 7 October 2006; if people think it would be helpful to include the traditional arrangement as well as the current, I'd be glad to restore that table, formatted to match the current article style. JeffConrad 08:14, 9 February 2007 (UTC)

Lázaro Gimena 12:43, 9 February 2007 (UTC)
First of all, I want to thank expressly, for not deleting the EV Chart. I have to beg your pardon, because I am new in "wiki" and it's been a hard work for me, just to understand how it works. But I insist of my gratitude.
Respect to the EV Chart, that is what it is, a chart; not a table, not a graph, not a picture, I will explain.
If you have the time to have a deep insight on it, you will realized that most basic concepts related in camera shots are simply explained and related.
Normally, "new" photographers, confuse all these values (see light gathered coment above as an example).
The fact is that the camera, grosso modo, have to receive an "amount of light" (light flow) to fix the image. It depends on the environment (outdoor or indoor, bright or dimmed scene, for example) to set the shutter speed and aperture area, obviously.
For the same light state (EV number given by the photometer) there are different options to capture this mentioned light measured: faster and bigger or slower and smaller (in terms of shutter speed and aperture).
There are also other factor that is involved, the "film (or LCD) sensitivity" which it is also expressed in the chart.
Respect to the JeffConrad's comment, I have to say that I agree that design, colors and "ornaments" could confuse at the first sight and can be improved.
But they are not casual:

  • decolorize from dark (grey) to bright (white) represents EV value (more or less light). Diagonal straight (thanks to algorithms) lines represents same light states or EV numbers. That's why if you take the shot above the line, the photo will be overexposed (more light than needed) and if it is below it will be underexposed (less light than needed).
  • I agree, clouds and sun, seem to be not very serious, but representative of some normal lighting conditions (Table 2).
  • It can also be seen that for a same state, the aperture chosen (with its corresponding speed-time) influence the depth of field represented by such kind of bow tie (wide or narrow).
  • Below the shutter speed, there is a representation of time (represented with yellow in different widths) shots and how it influence the nitid or blurred photo and also the need of tripod use.
  • There is also a rectangle that simulates the capacity that some cameras have (bracketing) to shoot varying a little bit the light conditions to avoid over and under exposure (it really takes three photos, normal, over and under, and you choose the best).

In the EV Chart there is no way to be confused once understood. Besides, there are not special maths procedure (at least superficially).
Thank you again, and hope this comment will clarify the EV Chart and could be useful for readers.
P.S. I've correct the errata.
Lázaro Gimena 12:43, 9 February 2007 (UTC)

[edit] Referencing styles

The WP:MOS allows both author-date ("Harvard") and endnote-style referencing; one style is no more proper than the other. The MOS specifically forbids changing from one style to another without prior discussion (see WP:CITE#HOW). We went through this same thing a while back; please don't do it again without some discussion and reasonable consensus.

The author-date system here essentially conforms to that described in the Chicago Manual of Style, 15th ed. I'm not especially fond of the coding style, either, but at present, the "Harvard" referencing templates have some issues. I'm certainly open to discussion on how to improve the current format, but far less receptive to capricious changes. JeffConrad 23:27, 16 March 2007 (UTC)

If the citation style is a real problem, then fine. You didn't have to revert both of my changes. My first edit didn't touch the references. This article still needs a clean up.
  • Join up the multi-line paragraphs into single lines like my first edit. It's the style generally followed on Wikipedia. Breaking a paragraph into multiple lines makes it more troublesome to edit and diffs aren't as easy to read. Just let everyone's web browsers do the line wrapping.
  • Replace all the HTML entities with their simple ASCII/Unicode equivalents. e.g &ldsqo;/&rdsqo; => "
  • I don't like the way the references are wikilinks that look just like all the other links in the article. That's confusing and deceptive, especially when the majority of other Wikipedia articles uses a different system.
  • I also don't like the mis-use of the reference tags to add "notes". Just put that stuff right in the text. The Sekonic "note" is just pointless.
  • I think the article also makes rather heavy use of HTML and table markup to tweak the appearance.
Still on the HTML issue, was this copied from a web page? Simplifying the markup would make the article easier to edit. As it is now, it's a mess. All I want to do is make this article more consistent with the rest of Wikipedia. --Imroy 23:55, 16 March 2007 (UTC)
Whether my choices were the best is open to question, but I assure you that none was capricious.
  • Ease of editing is in the eye of the beholder. I find the single-line paragraphs (such as here) much more confusing to edit. I also often use an external text editor, and for me, it's much easier to break the line. I rely on the UA to do the filling. Some of this may simply be habit; for years, I used troff, and failure to break input lines generally was considered bad style because it made editing with vi more difficult. I carried the practice over into HTML coding.
  • I strongly disagree with replacing the HTML quote entities with ASCII quotes. Opening and closing quotes aren't the same; although they may look similar in the default Wiki sans-serif font, the neutral quotes look awful if a user has specified a serif font in his user CSS file, or if the user prints a page using a serif font.
  • The Harvard templates give a similar appearance to the reference links used here. I originally had the references without links, but objections were raised, so I added the links. I'm open to a better approach. I've played with revised "Harvard" templates, but thus far, have found it quite a difficult task--programming in assembly language is easier.
  • The use of reference tags for footnotes is not a misuse--see WP:FOOT. As with many other articles, this one seems (to me) to benefit from having both references and footnotes. One of the primary reasons the Chicago Manual of Style suggests the author-date reference system is that endnote-style references and footnotes really don't mix, even in a paginated medium. In a non-paginated medium such as WP, the combination of footnotes and endnotes is simply a mess. Incidentally, the purpose of the Sekonic footnote is to support the claim that Sekonic use a K of 12.5. There is so much nonsense bandied about when discussing meter calibration that an authoritative reference seemed appropriate.
  • I agree that I've used a lot of table markup. I dislike including all this junk as much as anyone, but HTML table facilities are quite primitive, and wikitables even more so. For all of the terrible things said about troff and tbl (many of them justified), the tables were quite parametric, and could be accomplished with comparatively little markup. I originally used an HTML table, but someone wanted the wikitable style, so I used it. I made the decision to favor readability of the article over code minimization. Ideally, we would have both, but changes to the wikitable template would be required, and I didn't see that as my role to implement.
I'm as much a believer in clean code as anyone else, but not at the expense of proper presentation. Again, I'm open to improving the appearance and structure of the article, but I'd like to have some discussion prior to sweeping arbitrary stylistic changes. JeffConrad 01:17, 17 March 2007 (UTC)
I should have mentioned that my issue with Imroy's first edit was more with the elimination of the HTML entities than with reformatting the paragraphs. A few common characters (opening and closing quotes, and horizontal punctuation such as hyphens, minus signs, and em and en dashes) look the same in typewritten copy (i.e., ASCII) but are quite different in typeset copy. I think using the proper characters precludes ambiguity and improves readability, and I think readability takes precedence over simpler coding. Some others may disagree, however. JeffConrad 23:08, 17 March 2007 (UTC)

[edit] Exposure for circuses

Sources vary, but the one (ANSI PH2.7-1973, Photographic Exposure Guide) with the most specific recommendation for circuses, gives a value equivalent to EV 8 for ISO 100. A later version of that guide, ANSI PH2.7-1986, gives a value of EV 8–EV–9 for "Brightly lit sports events, stage shows, and the like" (included in the article's table), but makes no mention of circuses. The Kodak Professional Photoguide (Publication R-28, 1986), and Kodak's Existing-Light Photography (Publication KW-17, 1991) suggest values closer to EV 7. The recommendation could be broadened to include values from R-28, but doing so would properly require every other value to be re-examined as well. There probably are additional sources that merit equal consideration, so going beyond the current sources could be a bit of a project.

For now, I've revised the table to mention that the values for circuses and ice shows assume floodlighting. JeffConrad 02:22, 20 April 2007 (UTC)

[edit] EV as an indicator of camera settings

I don't get it. According to Table 1. faster shutter speed results in higher exposure value. While IMHO it should be the opposite. If we get 0 EV with 1/100 then setting shutter to 1/200 should give us -1 EV. The table is completely wrong i think. Can anybody correct me if I'm wrong? Jan Winnicki * 11:01, 30 September 2007 (UTC)

No, the table doesn't say that faster shutter speed results in higher exposure value; it says that faster shutter speed is a higher exposure value; that's what it means. Think of it this way: in higher light levels, your meter tells you to use a higher EV setting, to let less of that light into the camera, so you set a faster shutter speed. Dicklyon 15:59, 30 September 2007 (UTC)

[edit] Hasselblad gets all the credit?

Weren't Kodak Retinas the first cameras to use the LVS as it was originally known? Al Olson, who could probably provide authoritative sources, has written that the LVS was used on the IIc (1954) and the IIIc (1954). LVS was renamed EVS in '57 with the IIIC (1957). Doug Kerr has added the Ib (1954) and IB (1957). The Vitessa L (1954) has settings that are numerically equivalent to EV and an uncoupled light meter that gave a readout in EV (source: my Vitessa L). Seikosha introduced the MXL shutter in 1956. This had permanently-coupled LV/EV settings. The Aires 35-II-L, Konica III, Olympus LS/2C and Ricoh 500 (with "Triggermatic" rapid wind) all had the MXL. The MXL could be set to half LV settings. Because of the shutter speed series (eg 1/2, 1/5) the integer LVs did not all match to a standard aperture. (source: a 1957 article in US Camera about the Aires, Olympus, Ricoh and Konica cameras that used the Seikosha shutter with EV markings. The article refers to 'light value system also known as the exposure value system'.) Helen Bach 22:06, 11 October 2007 (UTC)