Archived posting to the Leica Users Group, 1999/09/25

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Subject: Re: [Leica] Digital Darkroom technique
From: Eric Welch <ewelch@ponyexpress.net>
Date: Sat, 25 Sep 1999 11:27:06 -0500

At 10:37 AM 9/25/99 -0400, Chandos Michael Brown wrote:
>Has anyone messed around with the Gaussian blur filter in PhotoShop?  I've 
>been experimenting with it in an attempt to knock the edge off apparent 
>grain in enlargements.  It seems to work surprisingly well.  I haven't 
>read about this anywhere. Any comments?

You'll also notice that it's very easy to knock off a lot of sharpness with 
that filter.

What I do to use Gaussian blur to reduce grain is to first convert the 
photo from RGB to LAB and then to apply Gaussian blur to the alpha and beta 
channels. Then I apply unsharp mask to the "L" channel. That seems to be an 
industry-wide way to reduce graininess and not reduce overall sharpness, 
especially with images from digital cameras.

Oh, I use it also to overcome apparent underexposure in a photo where there 
is an enormous amount of contrast. Such as a person with a window behind 
them that makes them look almost like a silhouette. You can really do 
amazing things with Photoshop, and Gaussian blur plus the other tools to 
remedy that. I make a grayscale mask of the highlights in a duplicate of 
the original image and then apply 5 or 6 Gaussian blur to the mask, and 
then import it as a selection and use color dodge via the mask to only 
bring up  the shadows. It really works!


Eric Welch
St. Joseph, MO

http://www.ponyexpress.net/~ewelch

As the vacationing Scot in Canada was heard to say,


"Weel, if yon's the size of yurr moose, Ah'd hate ta see the size of yurr
cats"