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Subject: Re: Exposure to the right and tone placement



Rags wrote:

In the example shown in your earlier post, 12 f/stops are mapped into 12 of 14 available bits. Naturally, by this definition each bit is one f/stop. Following this logic an 8-bit image can only hold 6 f/stops of light. This is a hard concept for my feeble mind. It doesn’t look that different to me. If I repeat it often enough it should become a fact. One bit equals one f/stop. One bit equals one f/stop. One bit equals one f/stop. I got it.

Rags,

I agree that there may be a communications gap here. I have carefully read and re-read this thread. I cannot find anywhere that anyone has said that the output data in the working color space has one bit per f-stop.

To clarify this let me say it this way.

RAW data directly from the chip does indeed contain one f-stop per bit. The use of the least significant bits are limited by noise and posterization.

However, the RAW conversion routine maps this RAW data into the output range of the standard working color space. The end user can map the dynamic range of the RAW linear energy output of chip into the visually near linear working color space. This mapping will vary with the brightness range of the specific scene. The brightness range of the original scene is mapped into the dynamic range of the working color space.

If you design a camera and put a non-linear amplifer between the chip and the A/D, then this linear energy output would not apply. Clearly in the Leaf case, the RAW output is linear with respect to energy input.

If I say it that way,can we agree on this?

Ray

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