Digital BW, The Print

If I have a system that processes one dimensional signals ( an image is 
a two dimensional signal) I want the largest number of bits possible in 
the A/D front end. The reason is dynamic range in the capture of the 
signal. For example if I have a signal that is expected to vary between 
0 and 1 volt and I capture it with an 8 bit A/D I by quantization level 
is about 4 mvolts. Now for some reason if the signal is weak or my 
setting is wrong and the peak signal is only 8 mvolts, I only use two 
bits - hence a very poor capture of the signal. If I on the other hand 
have a 16 bit A/D I have  (or a quantization level of 15 microvolts ) 
the 8 mvolt signal is using 9 bits. Hence my capture will reproduce the 
signal in a much more robust manner. If my follow on processing only has 
8 bit resolution, however, there is no advantage in carrying this extra 
bit.

The same thing is true in imaging radar processing (a topic which I am 
quite familiar and also hold two patents). You want the maximum number 
of bits possible in the front end where the signal or image is captured 
in order to obtain a faithful reproduction of the signal. After that 
there is no advantage in maintaining dynamic range beyond the final 
output of the system. It is not surprising that it is true in optical 
images as well. There is very good reason for the digital cameras and 
scanners to have a high dynamic range, but after the image has been 
captured and is to be printed on an inkjet printer ( or printed to 
silver paper for that matter ) 8 bits should be fine.

Truman

Andr\ufffd Vallejo wrote:

> The following post is reproduced from a message by Dan Margulis in another
> web forum I join. I decided to reproduce it here 'cose even the 
> subject has
> been discussed a lot here some time ago,it looks to me like a very
> enlightning about the subject ,written by someone who knows a lot 
> about the
> subject (he's the author of "Professional Photoshop-A guide to color
> correction",one of the best books I've read). Sure it started a long 
> thread
> in the forum,but that's the way it has to be...He gave me his ok for
> cross-posting.
> Andr\ufffd
>
>