Talk:Exposure range

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This article can be improved in many ways:

  • the article title is wrong, it should be Exposure latitude. Stops is the unit how you measure exposure latitude. It's like filing the article about "lenght" under "meter" - it's just wrong.
  • equasion - typo. One of many many typos.
  • "then we talk about the blacks being more like dark grays and the white have yellowish or blueish hue to them (depending if you are shooting outside or not) " - mixing up of colour temperature and latitude - bad.
  • "The colours are more blended into one another" - huh?
  • "Each stop is equal to 5.5 dB which is 550,000,000 times brighter than the lowest light level" - what? this makes no sense at all.
  • "Most TV's today such as various rear-projection and LCDs, have a 2000:1 contrast ratio about same as film" - bad bad grammar.
  • "Contrast ratio is the on/off difference. 1 is off and the high number is on" - this is a travesty.
  • "Digital video is only 1.45dB which is way lower than film" ??
  • "Video is pretty limited because it only has 145 million variations of different brightness level" - yep. of course. absolutely true numbers, no doubt at all about them...
  • Overall, the article seems to just be launch pad for the HDRI article.

Anybody with lots of time to fix it? Cheers! Peter S. 21:44, 30 September 2006 (UTC)

Absolutely agree with Peter.
I would change the article myself, if I had the knowledge. I have a good enough understanding of the subject to work with film, but to give a good explanation of this subject is difficult.
1. It has to restrain itself, and find out if the article is about F/T-Stops, or Dynamic range/Exposure latitude
2. It has to comply with the scientific standards regarding light
3. It has to comply with common film industry terms, that filmmakers understand and work with
4. It's still a pedia, and it has to be readable by layman.
5. This discussion should inspire knowledgeable users to write information in the article.
Judging from Peter S's post and arrogance, I bet he's a working cinematographer. We need people like that to write in the article.
-- 01:57, 26 November 2006 (UTC)
I've removed all the crap. Anyone who wants to add information relative to stops, feel free to do so. ~MDD4696 04:03, 6 December 2006 (UTC)

Red Camera section reads like ad, plus what are DPs?[edit]

Someone with knowledge please clean this up. DP links to a disambiguation page that doesn't help at all since I don't know what it means here. The red camera section reads just like a plug for the product. "Only" 17,500 USD ?!?! Kinda need some context if you are going to say ONLY 17,500! Maybe that is a great bargain, but don't see how it fits here in an encyclopedia article.

Peter S. says it all clearly.

Thanks --Fitzhugh 02:32, 25 October 2006 (UTC)

I've deleted this section. First of all, there is no camera yet to speak of or evaluate, so it's all just speculation and uncritical acceptance of promotional info. Second, an encyclopedic article on dynamic range and stops generally should be discussing imaging technologies, not specific cameras or sensors. I wouldn't expect discussion of Red here anymore than I would of a Panaflex, CineAlta, or Kodak's new 5201 stock - discussing film, video, CCDs, CMOSs, etc is what the article should be germane to. Specific products should be largely irrelevant. Girolamo Savonarola 20:14, 25 October 2006 (UTC)

bogus topic? delete article and redirect back to where it came from?[edit]

It appears that someone extracted a bit of unsourced text out of dynamic range to make this new unsourced article. I'm pretty familiar with photographic technology and terminology, but seldom hear the term "exposure range". In particular, this article talks about four or more different places where dynamic range is used in photography, but really only one or two of those is an exposure range. It's hard to fix the article to make sense without knowing where this comes from, but since it seem to only come from a bit of unsourced junk that some guy wrote a while back, it's probably best to just redirect it back to photography, which is somewhat less messed up now. Dicklyon (talk) 17:24, 23 November 2008 (UTC)

Alternatively, the article could be rewritten to focus on the actual exposure range (scene luminance dynamic range), or the limitation of the recording medium, the latitude. Suggestions? Dicklyon (talk) 17:43, 23 November 2008 (UTC)

Here is the diff where the scope of the article was changed from exposure range to the current ambiguous mess. It was unsourced before, too, so there was no basis for refining it, but this was a giant step sideways. Dicklyon (talk) 18:03, 23 November 2008 (UTC)

Here is a good book source, but it doesn't use either "exposure range" or "dynamic range" on this page. Dicklyon (talk) 18:45, 23 November 2008 (UTC)

Sounds fine by me. Girolamo Savonarola (talk) 19:45, 23 November 2008 (UTC)
Which? Delete? Rewrite? As is? Dicklyon (talk) 20:49, 23 November 2008 (UTC)
I think it is useful to have an article on general range-related issues in photography. It's a legitimate topic, which could benefit from expansion rather than deletion. Currently the photography article doesn't cover this topic at all, so simply redirecting there would not be a good idea. It sounds like the term "exposure range" is too narrow, so I would lean toward renaming this article to "Dynamic range (photography)" or "Dynamic range in photography". There is content at Dynamic_range#Photography which is not in this article, which should be included. Exposure latitude could be merged into Exposure (photography), and details of "exposure range" (narrowly defined) might also go there. It would certainly be helpful to cite sources that have authoritative definitions of these terms, though there may be multiple definitions in common use. -- Beland (talk) 22:01, 23 November 2008 (UTC)
Sounds like a good idea to have something like Dynamic range in photography; but does this article have anything useful to build from? Can't we stick with dynamic range#Photography until we find sources to expand it with? In my experience, it's difficult to find very sensible sources in this area, but we can try. For now, however, the content of this article is better covered under the photogrpahy section of the more appropriately tited dynamic range article. Dicklyon (talk) 22:23, 23 November 2008 (UTC)

(useful) log exposure range[edit]

From "The Manual of Photography", Ray 2000, p.311 - under "Exposure Latitude" :

  • "From the characteristic curve of a material, the separation on the log exposure axis between the maximum and minimum useful density points is termed the useful log exposure range. As stated above, the subject luminance ratio to be recorded determines the log exposure range given to the material. This may be less than, equal to or greater than the useful log exposure range the material can accommodate,..." (italics original) --Redbobblehat (talk) 16:37, 12 February 2009 (UTC)
Great, a source. In that case, I'd suppport moving it to "useful exposure range" or something like that, and re-focusing the content on that topic. Dicklyon (talk) 16:53, 12 February 2009 (UTC)
Thanks D :) Note Ray's italics = "log exposure range" ... but there's more :
...Ray then goes on to define Exposure latitude (in a terrible sentence!):
  • "If the log exposure range is less than the useful log exposure range ... then the exposure latitude of the material is the factor by which the ... camera exposure ... may be multiplied, without corresponding loss of highlight ... or shadow detail." (Ray 2000 p.311 [1] - italics original)
  • "Detail may be defined as discernible density differences in adjacent tones corresponding to resolved regions of the subject." (Ray 2000 p.311 - my italics)
Which I interpret as meaning exposure latitude is the 'safe exposure error', based on how much gamma-compressed detail in the toe (shadow) or shoulder (highlight) can be recovered from the negative. Thus exposure latitude might, for example, be conveniently expressed as "+/- 2EV" if you are willing to apply gamma correction to it! (caution: I'm not sure that it's mathematically accurate/possible to transcribe toe & shoulder curves as gamma functions ... perhaps there is a better word?) --Redbobblehat (talk) 18:00, 12 February 2009 (UTC)
"Conventionally, exposure latitude is expressed as tolerance in stops or exposure values (EV) relative to the optimum exposure. Colour reversal materials usually have a latitude of ± 0.5 EV or less, where ± 1 EV indicates a permissible error of double or half the optimum exposure. ... Ideally, reversal material should be exposed to within 0.3 EV of optimum." (Ray 2000 p.312) --Redbobblehat (talk) 15:57, 13 February 2009 (UTC)
Compared to film, video sensors have (AFAIK) a constant gamma response to exposure; they have no toe and no shoulder. Therefore the "useful log exposure range" (as gamma-defined by Ray) sits exactly between "black clip" and "white clip". However, video sensors suffer from dark noise (film does not) which reduces the SNR in shadows. This arguably reduces the "useful log exposure range", but requires a redefinition of the concept to include the SNR factor. Perhaps this is why dynamic range is the preferred term in video engineering ...? I also read somewhere (sorry can't find a ref) that the "dynamic range of film" would be the log exposure range of the linear gamma section inbetween the end of the toe and the beginning of the shoulder. --Redbobblehat (talk) 18:00, 12 February 2009 (UTC)
IMO all this would be much easier to explain with reference to some HD curve illustrations. I'm thinking that perhaps some sections in the characteristic curve article would be the best place to do it ? --Redbobblehat (talk) 18:00, 12 February 2009 (UTC)

  • "I found, together with my friend Mr. Driffeld, however, that for every plate there is a range of exposures during which the connection between the amount of silver and the exposure is so nearly logarithmic that no human eye could possibly detect the difference between the truth and the approximation. The more richly coated the plate, the wider is this range, and the more extended is the scale of gradations which the plate is capable of rendering truly." (F. Hurter "The Action of Light on the Sensitive Film" 1891 found in Hurter And Driffield Memorial Volume 1920 p.155 - my italics) --Redbobblehat (talk) 02:11, 2 March 2009 (UTC)
Here, Hurter is talking about the linear section of the HD curve, which corresponds exactly to Ray's "useful exposure range" and the "dynamic range" in video engineering. --Redbobblehat (talk) 02:11, 2 March 2009 (UTC)
R, I don't think you've made the right connection here. Yes, he is talking about the so-called straight-line portion of the HD curved. But the "useful exposure range" is much greater than this; probably an extra stop in the toe and perhaps two stops in the shoulder. What have you found on "useful exposure range"? Dicklyon (talk) 17:21, 3 March 2009 (UTC)
Here is a page with specific definitions of what points in the toe and the shoulder define the limits of useful exposure range. The Manual of Photography also shows a graph making it clear that it is more than the straight-line portion. Dicklyon (talk) 17:27, 3 March 2009 (UTC)
Good catch! thanks. Hurter makes a big thing out of the linear section giving "correct" exposure; eg. arguing against push/pull processing:
  • "It is clear, therefore, that these negatives do not illustrate in a very striking manner what they were intended to illustrate, namely, the great latitude in exposure. They do, however, illustrate another point, namely, the great latitude there is in the quality of prints acceptable to the eye, and the curious inability of the eye to judge numerical values of density differences. In this faulty perceptive power of the generality of eyes lies a great deal of the latitude of exposure." (Hurter & Driffield, Latitude In Exposure And Speed Of Plates, 1893, in Memorial Volume [2] p.184).
but you're right, other authors place a more subtle emphasis on the usefulness of the not-so-grey areas ;-) ... Could we say that useful exposure range = linear section +/- latitude (thinking of Ray p.311 quote above) emphasising the latitude's imperceptible deviation from the reciprocity law ? --Redbobblehat (talk) 23:40, 3 March 2009 (UTC)
How about "useful exposure range" = "optimum exposure range" +/- "latitude" (after Ray p.235312 above ... :-) ? --Redbobblehat (talk) 01:12, 4 March 2009 (UTC)
Ray didn't say anything there about optimum, nor is there any source to connect to the linear section as you suggest. Dicklyon (talk) 04:40, 4 March 2009 (UTC)
Apologies for incorrect page number above, my pdf needs recalibrating! :
  • "Conventionally, exposure latitude is expressed as tolerance in stops or exposure values (EV) relative to the optimum exposure. Colour reversal materials usually have a latitude of ± 0.5 EV or less, where ± 1 EV indicates a permissible error of double or half the optimum exposure. ... Ideally, reversal material should be exposed to within 0.3 EV of optimum." (Ray Manual... 2000 p.312)
Those latitudes are so small they must be based an exposure range, rather than the average optimum exposure ? I would be seriously worried if my reversal film had a useful exposure range of 0.6EV ... --Redbobblehat (talk) 19:51, 4 March 2009 (UTC)