Digital BW, The Print

Hi Todd-

As has been discussed here (or was it on the scanner list, I can't keep them
straight ;^),  the fact that a jpeg or sizing transform "smoothes" the
histogram does not make a better image.  It just makes a muddier image.
However, it does not follow that the original, posterized image is equal to
the same image produced in such a way that the original, smooth tones *and
detail* are maintained.

The histogram is not the holy grail- it is just another measure of image
quality, that may or may not be important to a particular image.  However, a
process that consistently lowers a measure of image quality (such as the
histogram) is suspect.

Bill Morse
PhotoProspect
Cambridge, MA 02139

on 3/23/02 1:38 PM, Todd Flashner wrote:

True, the histograms get rewritten, much as a resizing, rotation, or blur
would do. To my mind that just furthers the point that for much image
editing the histogram is NOT a good indicator of image quality, precisely
because it is so easy to make a good histogram from a bad image.

> What do you think?  I histogramed those two images, and they both have full
> histograms, up until they cutoff, not having the white shirt collar in
> them...so even if the posterization exists in the .tiff files, it doesn't in
> the .jpegs...

The question then becomes, does jpeging actually make a bad "image" look
better? IOW, if the IMAGE itself actually VISIBLY shows posterization will
jpeging that image ameliorate the posterization, as it's smoothed histogram
would suggest? It's a good question, worthy of some testing, and I don't
honestly know the answer.  My suspicion is that that you'd actually end up
with the ironic situation of an image looking worse while the histogram
looks better - but that's purely speculative on my part.






[Non-text portions of this message have been removed]