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

Jeff Schewe Wrote:

"Again what you are missing is the linear nature of digital and the fact that SO MUCH CRITICAL data is recorded in that brightest stop. Yes, you can meter for the highlights and then open up, but how much? 3-4 stops is simply too imprecise. Is it 3 stops or 4 stops for your sensor to record a textured highlight? If is 4 and you only open 3 stops then you've lost a full 1/2 of all the levels your sensor can capture."


As I said, the amount to open up depends on testing, just like Ansel Adams did with film.

One can easily determine the characteristic curve of his/her camera by taking a picture of a gray card at indicated exposure and bracketing in 1/3 stop increments from that value. For this experiment I converted raw images in AdobePS Camera Raw with default settings.

I got this idea from an energetic photographer with an engineering background who is active in the Nikon forums:

I did this for my Nikon D70 and the results are shown in linear-log:

and log-log format:

As you can see from the linear-log plot, to place a value at Zone I would require opening up about 2.4 stops, which I think is very close to the value Bruce quoted for his Canon.

Despite your protestations to the contrary, I think that the same principles we learned with film are directly applicable to digital once one takes into account the characteristics of the medium.


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