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Maniac (V) Mad Scientist

Insane since: Aug 2000

posted posted 02-01-2005 20:07

Was talking about High Pass and things over at Photoshop Cafe. Phil, the basterd, got it into his head to question my technique. The audacity!

After some back-n-forth, nailed down his beef with my technique. It was simply my suggestion of using Channel Mixer 33/33/33 to desaturate after High Pass. I went with CM because I have issues with other ways of desaturating for this (especially those based on human perception).

After realizing the errors of my ways and some thinking, I came up with a way that I am *very* happy with. I have yet to see this new way fall down. I even tried to trip it up on purpose and it still came through like a champ.

Copy photo
High Pass it
New layer
Fill with 50% grey
Set blending mode to Difference
Copy merged and paste

Should have lots of black and the start of Snowy Mask right about now.

I'm not going to get into how's and why's of this method of desaturating just yet, so beer with me. All I'm going to say right now is that it works on maximum difference.

On this new layer, do Finding MaxRGB.
In case you need a refresher:

Finding MaxRGB

Start with a photo.
Go to the Channels palette and copy R.
Should be something like 'Red copy' by default.
Still on Red copy, hit Image > Apply Image.
Channel: Green
Mode: Lighten
and hit Okay.

What you have just done is compared R to G and taken the greater of the two on a pixel-by-pixel basis. Let's do the same with G.

Still on Red copy that has just been ChOp'ed, Image > Apply Image again.
Channel: Blue
Mode: Lighten

Now what you should have is the greater of R, G, and B in a nice greyscale.

Once you have that done, just invert it, copy and paste into Channels palette, or whatever.
In some cases, depending on how high you went with High Pass, might have to compliment with Find Edges.

Since I'm not PS CS, I have to use it with regular Gaussian Blur. I would really love to try it with Lens Blur, but not today. Even with regular ol' Gauss, it's working damn dandy. It's even good where other methods of desaturating would have problems.

I'm happy.
And thanks to Phil for pushing.

Bipolar (III) Inmate

From: Vancouver, BC Canada
Insane since: Apr 2002

posted posted 02-02-2005 11:12
quote: beer with me.


Nice stuff wj.

Maniac (V) Inmate

From: The Pool Of Life
Insane since: Nov 2003

posted posted 02-02-2005 22:40

I have never tried this before warj, nice stuff thanks loads. I can see me using this tech' on more than a few occasions.

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