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Subject: Re: raw 3.1 professional custom profiles for highend digital cameras



Bruce,

I greatly admire your published work in digital photography and over the years have had the benefit of several editions of Real World PS, both of the camera raw books and the second edition of color management and consider them the best in their categories.

That said, sometimes approaching things from a different perspective is useful. "16 bits would be a little more forgiving than 12" is a bit of an understatement since 16 bits gives 65536 levels compared to the 4096 levels in 12 bit--it would take exposing to the right to new heights. However, once we record the full dynamic range of the subject, we usually set a black point, which now becomes zero and the whole histogram is shifted to the left and we no longer have so many bits to record all that exquisite highlight detail in much finer steps than the eye can differentiate since the eye responds in a log fashion, not linear. In this matter I agree with Norman Koren:



"I mostly agree with the Luminous-Landscape.com article, Expose (to the) Right, which recommends setting the exposure to the maximum value that doesn't burn out highlights. (This applies only to images saved in RAW format.) However I wouldn't go too far. A little margin doesn't hurt; there are plenty of levels in 12-bit A-to-D converters. In extreme situations, you may want to make two exposures and combine them."

Jeff,

Film has one advantage over digital: it responds to light in a log fashion, the same as our eyes. Linear recording wastes many bits in the highlights by recording more gradations that our eyes can differentiate and not enough in the shadow areas where our eyes can detect small realative differences in intensity. A log scale is more efficient. See Poynton's gamma FAQ



In addition film has knees and shoulders which gently roll off gradations at the extremes, whereas digital exhibits abrupt clipping in these areas.

In the Nikon forums there are a lot of tone curves which attempt to simulate the appearance of Reala, Provia, and Velvia. Apparently some people like the film look.

Bill

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