Archived posting to the Leica Users Group, 2001/04/08
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
> [How to use photoshop to simulate stocking-over-a-lens diffusion]
You need to create a density mask of the highlights, g-blur it
and then mix it in as a new layer.
In detail (assuming you are working with a RGB colour image):
1. Go to the 'channels' panel and cmd-click on the RGB channel
(wintel losers use alt-click)
2. This will select the upper 50% brightness range of the image.
To soften the selection edges, feather the selection a radius
of 8 pixels (use the command under the 'selection' menu)
3. Create a new layer of this feathered selection (cmd-j)
4. g-blur the new layer with a radius of 4 pixels
5. Then use the 'opacity' slider on the layers panel to decide
how much diffusion to add
What I like about the above technique is that the diffusion is
picked up in the highlights only and not the entire image - just
like in real life with a stocking over the lens. Also, because
of the opacity slider you can add as much or as little diffusion
as you like.
Another example why photoshop leaves dankroom photography back
in the dark ages. :?)
Regds,
Andrew Nemeth
<http://4020.net> -> photos, 360° panoramic vrs, sounds
<http://nemeng.com> -> vr java applets, leica faq, tech info