On 11.12.2007, at 18:06, Alessandro Sabatelli wrote:
/Developer/Examples/Quartz Composer/Compositions/Interactive/
Histogram.qtz
You may want to use an "Image Resize" before the Image Histogram to
ensure good performance
on large images.
... which basically is the reason why such "Histograms" suck for real
adjustment work. Aperture is an example of an rather unusuable
histogram.
Imagine a simple image with black and white stripes 1 px. wide
alternating.
The real histogram are two bars at the far edges of the histogram
(lets name their position 0 and 100).
if the intermediate rep. is scaled by 50%, you get one bar in the
middle (50). At 33 % two bars at 33 and 67.
Given the orig. image is wide enough, there will be scales where the
"histogram" will show uniform distribution or varying curves.
However, there is only one scale where the bars are correct, and that
is 100%
NONE of them have anything to do with an original histogram.
Does it matter for evenly distributed images? Probably not.
Does it matter for feature rich high contrast available light images?
You better bet on it. There is no way with that kind of "histogram" to
adjust EXACTLY to the point where still (noise) detail is visible at
the shady part or guaranteed no precision loss is before the
highlights clip.
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