[Leica] Re: "the dynamic range of digital"

[schneiderpix at mac.com (Robert Schneider)]

Hoppy,

Granted, I'm assuming that the engineers at Adobe knows something  
about the software they design and the raw material that software is  
supposed to work with.  In addition, I'm assuming that not even the  
world-class electrical engineers at Leica have figured out how to  
overcome the laws of physics.  I may be wrong on both counts, but  
here is a whitepaper published by Adobe on RAW capture and linear  
gamma.  In particular, read the first two paragraphs on page three:

Linear capture

You may be tempted to underexpose images to avoid blowing out the  
highlights, but if you do, you?re wasting a lot of the bits the  
camera can capture, and you?re running a significant risk of  
introducing noise in the midtones and shadows. If you underexpose in  
an attempt to hold highlight detail, and then find that you have to  
open up the shadows in the raw conversion, you have to spread those  
64 levels in the darkest stop over a wider tonal range, which  
exaggerates noise and invites posterization.

Correct exposure is at least as important with digital capture as it  
is with film, but in the digital realm, correct exposure means  
keeping the highlights as close as possible to blowing out, without  
actually doing so. Some photographers refer to this concept as  
?Expose to the Right? because you want to make sure that your  
highlights fall as close to the right side of the histogram as possible.

HTH,

Rob



Hoppy wrote:


Date: Tue Sep 19 21:26:38 2006


Robert, I understand the linear part and the 50% of tones within the  
first
(brightest) stop. I don't follow why UNDER exposure
causes loss in that stop. Isn't the underexpose method meant to  
preserve as
many of those tones as possible? Then you are going to
adjust your tonal range after capture so that the 256 possible are  
chosen
from the ones you have captured. In other words, a nice
smooth histogram with no gaps after you manipulate the image. I think  
this
is the key point not being considered and resulting in
the polarised viewpoints. Not what the file will look like un-altered
afterwards to compensate for the underexposure, but how many
tones you have captured. If a "normal" exposure results in clipping  
say half
of the brightest f stop approaching 255, aren't you
losing far more tones than clipping half a stop from the bottom  
approaching
0?

There must be something I am missing here, and I really want to  
understand.

Cheers
Hoppy

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Robert Schneider Photography
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