Apache-Talk @lexa.ru 

Inet-Admins @info.east.ru 

Filmscanners @halftone.co.uk 

Security-alerts @yandex-team.ru 

nginx-ru @sysoev.ru 




      :: Filmscanners
Filmscanners mailing list archive (filmscanners@halftone.co.uk)

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[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.

From: "Arthur Entlich" <artistik@shaw.ca>

Unsubscribe by mail to listserver@halftone.co.uk, with 'unsubscribe 
or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or 


Copyright © Lexa Software, 1996-2009.