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[filmscanners] Re: Advice on scanner settings
> Anyone have a good idea how to check two images for changes against one
> another such that hue, color, contrast, brightness or any value change
> to a pixel would show up clearly as a changed pixel when comparing two
> images on top of one another? I would like to see a quantitative
> visual indication of each pixel that is altered by a certain jpeg
> setting relative to the non-jpegged tiff.
>
Isn't that what the 'difference' blend mode in Photoshop does ? I've only
played with it a few times.
> For instance, I am wondering if jpeg 12 on the Photoshop scale is near
> lossless or not. A jpeg 12 in Photoshop seems to be a 3:1 compression,
> but I am not sure how much damage it is doing.
I've used Irfanview in a talk to demonstrate the loss of colors when
converting to jpg. If I remember correctly, the number of different colors
went down from about 1 million to 500, 000 when converting from a tiff to a
fine jpg. It tells you the number of different colors in any image. So you
have a quantitative value for the 'damage'.
bob Frost.
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From: "Arthur Entlich" <artistik@shaw.ca>
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