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Regarding the gamma specification called BT.1886, this could be taken into consideration only in video editing or can be used in still image editing as well, are there some limitations?

I've found an article that expose a pretty documented way of setting the gamma value. (please read the chapter Setting gamma correctly) Thanks

user124853
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ITU-R BT.1886 defines the reference electro-optical transfer function (EOTF / EOCF) for CRT and LCD displays used in HDTV studio production.

It was made in an effort to officially specify and standardise CRT EOCF and thus adopts a gamma of 2.4.

It should be used on HDTV reference mastering displays and is usually associated with BT.709 opto-electrical transfer function (OETF / OECF) that HDTV cameras adopts. The combination of both produces an overall colour imaging system gamma (end-to-end gamma) of 1.2 which is suitable for dim / very dim viewing conditions such as when you are watching television.

BT_709_BT_1886_EtE_Gamma

Considering the above, BT.1886 is indeed defined for video applications. It has a stronger gamma than sRGB EOCF (2.2) which is dedicated for desktop graphics applications.

sRGB_BT_1886_EOCF

Theoretically you should not use BT.1886 for image editing tasks that target desktop graphics but sRGB EOCF.

Kel Solaar
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  • thank you! in your oppinion why it's a bad approach to calibrate/use a LCD for still image editing at BT.1886? as far as I've read the gamma value it's somwhere between 2.3-2.4 (sRGB having 2.2 according to some sources) – user124853 Mar 21 '16 at 21:07
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    BT.1886 adopts a 2.4 gamma. If you edit your images under that gamma they will lack of contrast (and colourfulness) when viewed on a consumer desktop graphics which will very likely have a 2.2 gamma (sRGB EOCF).

    To make matter worse, the viewing conditions practised in HD Mastering are very dim: surround luminance is usually 1% of white reference that has value of 100-120 cd.m-2 so if you were to work in such viewing conditions and exhibited your work on a display with average surround (as defined in sRGB specification) your images would look quite washed off.

     – Kel Solaar Mar 22 '16 at 07:50
  • Thanks,I am pretty confused;Assuming that we have an 8-bit LCD, which does not have gamma correction at all—or does not allow the gamma to be set enough closely to taget—and also does not use editable internal 1D LUT, If you calibrate your LCD for gamma 2.2(sRGB)the DisplayCAL will make your LCD loose colour depth because it does not offer any interactive gamma adjustment.Therefore your LCD won't even be 8bit anymore (more like 7,5bit, for example).Creating 1D LUT for video card (8bit to 8bit) will only cut your colour depth. (by Pinhollow Euri); – user124853 Mar 22 '16 at 09:55
  • So, I thought that calibrating at native gamma value, (2.43 in my case) or using BT.1886, could be a good approach in calibratig for editing/viewing still images. – user124853 Mar 22 '16 at 10:12

  • "which does not have gamma correction at all"

    This is why you are probably confused, characteristics of LCD are indeed intrinsically linear BUT they always do impose a gamma correction through circuitry, mimicking the CRT power response. This has multiple advantages the main one being enabling perceptual uniformity / coding. I would suggest that you roam a bit on Charles Poynton website, specifically around that url: http://www.poynton.com/notes/Timo/Perceptual_uniformity.html

     – Kel Solaar Mar 22 '16 at 18:23
  • Thank you, I'll read Mr. Poynton's pages and faq's about gamma. Hope to understand all these and apply because I am still not sure, where is the true (2.43 native, without 1D LUT or sRGB 2.2) – user124853 Mar 22 '16 at 19:11
  • Unfortunately there are not facts that could guide us to an answer when it comes to choosing the "right" gamma value between 2.2, native or other value; anyway regarding this question, your answer helped me to exclude the BT1886 from equation taking in consideration photo editing/web not Video editing. – user124853 Mar 29 '16 at 13:47