Digital BW, The Print

A number 12 (yellow) filter is also called a minus blue filter because 
it filters out almost all of the blue light in the spectrum. It's 
normally used to darken the sky and deepen shadows- since shadows tend 
to be illuminated with light from open sky. To enhance shadows sometimes 
a blue filter is used. Sometimes using a blue filter will minimize the 
small shadows in a portrait - hence minimizing the impact of lines, 
wrinkles, etc.

So there is some information in the blue channel, but it is going to be 
very dependent on the photograph.

Truman

Alan.Huntley@... wrote:

> Mitch,
>
> I read of a very similar technique to yours on the imagingrevue 
> website. However, the Blue channel was not used; just Red and Green. 
> Seems to make sense if one looks at the Blue channel alone...it 
> doesn't seem to have much to offer.
>
> But, one additional step that's not posted below is to convert to Lab 
> and copy/paste the Luminosity channel. This particular step gives you 
> something that Channel Mixer doesn't. You might want to give this a 
> try, too.
>
> I've been playing around with this convert technique for a couple of 
> days and, at least, initially, I have to agree that it seems better 
> than other techniques I've used.
>
> Alan Huntley
>
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