[filmscanners] RE: JPG sharpening [was: Color spaces for different purposes]

["Laurie Solomon" <laurie@advancenet.net>]

Really good answer Robert.

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Robert Meier
Sent: Sunday, June 09, 2002 11:27 AM
To: laurie@advancenet.net
Subject: [filmscanners] RE: JPG sharpening [was: Color spaces for
different purposes]




> -----Original Message-----
> So, aside of asking for any observation regarding improving my
> workflow - why is the sharpening so much more effective on the smaller
> image?

In PS there are three parameters for USM. One of them is the radius. The
bigger the radius the more surounding pixels are taken into account for
sharpening. Now if you downsample your image it is kind of like compressing
mutliple pixels into one pixel. For USM that has the same effect as
increasing the radius. Therefore, if you use the same radius for the
original image and the downsampled image then the effect of sharpening will
be stronger for the downsampled image. Maybe this is what you see. Make sure
you also play with the other two parameters.

Robert

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