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View Full Version : Basing blur-size on a grayscale map... possible?


Laserschwert
09-05-2004, 01:14 AM
I am wondering if there's way / plugin which allows you to blur an image based on the luminance of another layer. Like when you have photograph, and want it's center to be sharp, and getting blurrier towards the edges. Of course you can do it by "hand blurring", but I'd like to have a little more automation in some cases.

Taking just two layers - one blurred, one not - putting the sharp layer on top of the blurred one, and giving the upper layer a layer-mask with a radial gradient, which makes the "sharp layer" become more transparent towards the edges wouldn't work, because the amount of blur on the underlying layer wouldn't change, and you would just get a partially-transparent sharp layer on top of a blurred layer... which is not the same.

I was thinking of a tool which takes the luminance of another layer or image, and you enter a blur-radius for black and one for white, and it blurs the image according to these values.

Does anybody understand what I mean?

Ian Jones
09-05-2004, 01:30 AM
It's known in the effects industry as a 'compound blur'. I think photoshop 7 (I use 6) has a 'lens blur' which does the same thing. Does that help? Adobe after fx has compound blur... if you have it.

WDABUILDERS
09-05-2004, 03:37 AM
The lens blur filter works for a rounded edge blur effect.

If your are looking for depth based on luminance, create a mask from a channel, apply it to the blurred image and adjust with levels, curves or brightness and contrast. If you really need two levels of blur radius you could apply the mask to another blur layer and invert the mask to cover the areas not masked by the first.

rgrds
WDA

LiQ
09-05-2004, 03:50 AM
OMG I have often wondered this too. Adobe SOOOOO have to put in the next release!

I mean really, it should have been in there ages ago! :p

halo
09-05-2004, 09:41 AM
your talking about lens blur which started shipping in PS CS. You can use any greyscale image to generate blur (and blurs are always round unless they have direction)...you can use any variation on greyscale maps to drive the blur value, such as z buffer to get depth of field, or a radial gradient to drive a vas'd lens effect.

Diffuse glow however is something else.

Laserschwert
09-05-2004, 12:56 PM
Right, I wasn't just looking for a tool to blur the edges, that was just an example. I was actually thinking about using a Z-Buffer map from MAX maybe, to put DOF on another image... there are lots of things to do with it.

I'll look into CS for this.

Stroker
09-05-2004, 02:26 PM
Lens Blur rocks. Mostly certaintly can be used for post DOF with a z render - and actually looks good.
Has other cool uses.
There were a few decent tutorials floating around out there, but I can't seem to find any. Decent ones, that is.

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