New article on color management

Started Apr 26, 2013 | Discussions thread
OP gollywop Veteran Member • Posts: 8,269
Re: Yeah...

Great Bustard wrote:

gollywop wrote:

Great Bustard wrote:

What I'm asking, I guess, is if 16 bit sRGB will ever have any practical advantage over a larger 16 bit colorspace due to the finer gradations of the colors it does represent.

Well, I have certainly encountered significant posterization in large expanses of blue skies under aggressive tone mapping when PP-ing an 8-bit sRGB jpeg.  This is not an uncommon experience.

For sure.  But I'm talking about 16 bit files.

And, unfortunately, once an image starts life as an 8-bit image, you don't gain a heck of a lot just converting to 16 bits; all those gradations in between don't suddenly get created.  If you're going to use 16-bits with sRGB, you want to shoot raw and process with 16-bits from the outset.

That's what I mean.  Will sRGB ever have an advantage over aRGB or PPRGB due to it's finer gradations under those circumstances?

As to just what color differences humans can see, and how fine practical gradations can be, we humans are apparently much more sensitive to small shifts in blues than reds, and more in reds than greens. So the whole notion of JND (just noticeable difference) in color is very wavelength related. Clearly going to 16-bits is a huge boost. It gives a 256 fold increase in the number of divisions over 8-bits, and none of the color spaces is anywhere nearly 256 times larger in linear dimension.

You can get an idea of all this from the MacAdam ellipses:

but beware in assessing the diagram they give there that they have exaggerated the sizes of the ellipses ten fold.

I'm fully aware of the advantages of 16 bits vs 8 bits.  What I'm wondering is if 16 bits representing a less expansive colorspace might not have advantages, on occasion, over 16 bits representing a larger colorspace, due to the finer gradations of the smaller colorspace.

If any advantage existed, it could only be for an image that lay completely within the sRGB gamut to begin with.  I don't recall ever having used a wider gamut (with 16-bits) on such an image that would have benefited from using sRGB.  However, one can speculate that, if any such advantage existed, it would occur if it were necessary to massively expand the tonal range during processing.  This might occur, for example, if one had shot a very high DR scene very dark to preserve highlights, with a major part of the image down a number of EV.  A large so-called exposure compression in such a case might benefit from having a 16-bit sRGB instead of a 16-bit something broader.

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