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Subject: Re: Exposure to the right and tone placement



"The practicle[sic] effect of the D70 lossy compression is that your test is flawed for cameras whose compression scheme is lossless"

The test is not flawed for cameras with lossless compression--it is not applicable to such cameras. However, according to Steve's figures there are still 161 levels in the 2049-4096 range and this is sufficient to make the point. The test also demonstrates that there is not that much headroom between zone V and zone IX, about 2.2 EV according to Bruce's tests for his Canon, which is very close to what I found in my previous testing with the D70. Totally blown highlights are completely lost and can not be recovered, whereas the lower tones do contain data.

"For "normal" tone curved images-ei, jpegs from the camera, the effect is indeed "visually lossless" since the tone mapping throws away excess levels in the highlights."

I wasn't aware that the compression technique for raw capture (NEF) was used for jpegs, so this comment may be superflous. Why would you apply NEF compression to jpegs; doesn't jpeg have its own method of compression?

"But, when shooting raw and wishing to delpoy an advanced tone curve to remap highlight detail, the D70 lossy compression leaves you with considerably less than the full 2048 levels of the brightest stop. That makes hilight tone mapping with the d70's compression less useful."

Quite true, but it would take some pretty fancy mapping to make full use of all the 2048 levels. The advantage of non compressed files may be more theoretical than practical. I would like to see some examples.

As for Rags' comments, it appears that anyone who does not agree with your assertions does not undestand linear capture. Nonetheless, Rags does offer some valuable insights. Of course, Thomas Knoll is an undisputed master of digital imaging. Michael Reichman referred to Mr. Knoll's thoughts regarding the brightest stop's information in his treatise "expose to the right", but I haven't had the pleasure of communicating with him on this subject and exploring his thoughts on exposure, blown highlights and noisy shadows.

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