Talk:Exposing to the right

message: Refer to http://en.wikipedia.org/wiki/Talk:Exposing_to_the_left  — Preceding unsigned comment added by 2.30.163.217 (talk) 22:59, 29 August 2013 (UTC)
thread_title:  ETTL? =

message: The premise behind ETTR is the falicy that each bit records a different zone of f stop of light thus meaning the last bit of a 14-bit raw file records massive detail all in the highlights. This is of course an absolute absurdity to anyone who has even a basic understanding of how semiconductors and digitization works but this article makes no mention of it.  — Preceding unsigned comment added by 68.150.59.159 (talk) 01:49, 15 August 2011 (UTC)
replies: text: You are wrong, or perhaps you have simply misunderstood. I'm trying to make the article clearer. Please let me know what you think. Regards, nagualdesign (talk) 00:19, 26 November 2011 (UTC)
thread_title: Criticism

message: Eagle-eyed experts may have spotted that the image histograms are non-linear, whereas ETTR deals entirely with in-camera, linear histograms that are subsequently processed in a RAW converter (also linear) before being exported to Photoshop (other non-linear editors are available). A more accurate image of an ETTR histogram would look almost exactly like the 'normal' histogram but shifted to the right, without being stretched out. The same mistake is made on the Luminous Landscapes website, which I reproduced without thinking. Would anybody like me to change the image to avoid confusion? Conversely, does any body think that changing the image would be more confusing? ..I realize that I may be talking to myself here. nagualdesign (talk) 00:19, 26 November 2011 (UTC)
replies: text: Apologies for my impatience but I decided to swap the Photoshop-style, non-linear histograms for Canon EOS-style, linear histograms. It's more technically correct, even though it does not look like the ones on the Luminous Landscape website. nagualdesign (talk) 04:34, 26 November 2011 (UTC)

text: I'm not sure about those histograms divided into five sections (which I presume relate to the nominal 5-stop range of the camera discussed). Surely the point of ETTR is that those stop dividers should be drawn at 16,32,64,128, illustrating that each higher stop uses twice the number space range of its predecessor? GideonReade (talk) 15:26, 1 January 2012 (UTC)
replies: text: The 5-segment histograms are copied off my EOS 600D. I also presumed that each line represented +/-1EV, and a quick test confirms this, yet the camera can take photos with more than 5 stops range. Go figure. (Something to do with the histogram being based on a jpg, rather than the actual raw data.) The only bit of BS are the gradients underneath, which are non-linear and inaccurate. They don't really belong there, strictly speaking, but they give a quick idea of how to read the histograms (that they run from dark to light). nagualdesign (talk) 09:24, 2 January 2012 (UTC)
thread_title: Histograms

message: I have amended the article as the reasons given for the disputed validity of this technique misrepresent the concept. I expect that this is due to misconceptions rather than a blatant straw man argument, so I'll attempt to explain it here and, hopefully, a better way of describing the technique may result, so that others do not have the same misconceptions.
1) "The basic principle, that the lighter tones in an image contain more information than the darker tones is not consistent with the physical realities of image sensors and their operation." Of course any tone may be considered to be a single piece of information - the tonal value (a number). What ETTR actually says is that the range of tonal values describing the lightest tones (the first 'stop') is larger than the range of tonal values that describe the darkest tones.
2) "A connection is made between the fact that a difference of 1 stop represents a doubling or halving of exposure, while the assumption is made that the same principle is applies to the image sensor and the way it records information." The sensor does not record information, it collects light. More properly, it converts light into electric charge. Double the light exposure and you double the charge (up to a limit). This charge is then digitized (converted to a number), such that a doubling of the number represents a doubling of the light exposure. In reality the accumulation of charge and the digitizing process may not precisely follow this rule due to physical limitations and the methods employed to mitigate these limitations, but the basic principle is valid. After digitization these values may be gamma corrected and then recorded (as in a JPEG), at which point we have gone beyond the scope of ETTR (which deals purely with RAW data).
3) "The image sensor will, however, (depending on its design and features) use between 8 and 16 bits of information to record the brightness of a given pixel in the image. If we assume an 8-bit sensor, and for the time being ignore the color of the image, the available brightness values are 0-255. Fully black will be recorded as 0000 0000(binary) = 0(decimal), white will be recorded as 1111 1111 (binary) = 255(decimal). In both cases we see that the image sensor uses 8 bits to record the information, irregardless of the actual value being recorded." As noted above a single tonal value (be it black, white or any shade in between) is indeed represented by a single number, however mid-gray (in this regime) would be represented not as the mid-value, 128(decimal), but by a much smaller number. This would leave many more tonal values available to describe the upper 'half' of the sensor's range of sensitivity as the lower 'half'.
4) "In ETTR, it is assumed that the part of the image with the highest light intensity uses half of the available recording values.." No it isn't. No 'part of the image' uses half of the available recording values. It's the range of tones which describe the highest stop of light sensitivity that use half of the available tonal values.
5) Inserting phrases such as "are said to", "it is assumed", etc. when describing the proposed technique, and making assertions such as "is not consistent with the physical realities.." when rebutting the technique smacks of POV.
Please comment below before making changes to undermine the article. Regards, nagualdesign (talk) 00:04, 6 March 2012 (UTC)
thread_title:  Misconceptions 

message: I've reverted a lot of the edits made recently as there were a few misconceptions being banded about. The facts about signal-to-noise ratio were already mentioned in the opening paragraph, including the reference to Emil Martinec's work. Representing it as an 'important paper' that all but debunks Michael Reichmann and Thomas Knoll is wrong, however. That paper actually shows that ETTR works in the simple case of overexposing (within limits) and then globally stopping down an image in post-processing, compared to simply taking a normal exposure. However, it does not deal with cases in which an image is processed via dodging and burning and other techniques, which any photographer will tell you is the very reason they shoot in ETTR: Latitude.
When burning (or otherwise darkening) part of an image you are in effect discarding data, whereas when dodging (or otherwise lightening) part of an image you're often attempting to represent or reconstruct data that really isn't there, having been lost in the noise or, in the case of adding fill light to dark areas, having been poorly digitized in the first place. To put it simply, by overexposing in the first place nothing needs to be lightened in post. If you'd like to quote the section(s) of the paper that you referenced which you think demonstrates the 'misdirected reasoning' of Reichmann and Knoll, perhaps we can discuss how the article might be improved. nagualdesign 01:31, 31 December 2015 (UTC)
thread_title:  Further misconceptions