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For raster layers that are partly transparent, the lens blur filter is creating halos. It’s hard to describe in words, so here are instructions on how to cause the symptom.
1. Create a blank file (say, 500×500 pixels)
2. Add a solid black color fill layer.
3. Above that create a blank (transparent) raster layer. Make sure that layer is the active layer
4. Use the rectangular marquee tool to select roughly 250×250 pixel rectangle.
5. Fill that rectangle with black.
At this point you should have two layers. The bottom layer is solid black, and the top layer is a black square. So it all looks black.
6. Do a lens blur on the raster layer with the black rectangle. It doesn’t really matter what the lens blur parameters are–just make sure you make the rectangle fairly blurry–maybe 25-50 radius.
Now you know longer see pure black. As the lens blur filter blurred the rectangle into the transparent parts of the raster layer, it added in some lighter non-black colors. For comparison sake, regular Gaussian blur doesn’t have this problem.
Up until CS3, lens blur was totally unable to blur the transparency of a layer. Now it’s able to blur transparency, but in so doing, it’s contaminating the image with some white color (if you do the above experiment with white on white, there’s no problems.)
Another interesting trait–this only happens if the object being blurred has sharp edges–ie., the transparency goes from 0% to 100% with no in-between transparencies. So if you barely feather or blur the edges of the object with a minute amount of, say, Gaussian blur (0.2 pixel), then apply the lens blur, the halo problem doesn’t occur.
Bart
1. Create a blank file (say, 500×500 pixels)
2. Add a solid black color fill layer.
3. Above that create a blank (transparent) raster layer. Make sure that layer is the active layer
4. Use the rectangular marquee tool to select roughly 250×250 pixel rectangle.
5. Fill that rectangle with black.
At this point you should have two layers. The bottom layer is solid black, and the top layer is a black square. So it all looks black.
6. Do a lens blur on the raster layer with the black rectangle. It doesn’t really matter what the lens blur parameters are–just make sure you make the rectangle fairly blurry–maybe 25-50 radius.
Now you know longer see pure black. As the lens blur filter blurred the rectangle into the transparent parts of the raster layer, it added in some lighter non-black colors. For comparison sake, regular Gaussian blur doesn’t have this problem.
Up until CS3, lens blur was totally unable to blur the transparency of a layer. Now it’s able to blur transparency, but in so doing, it’s contaminating the image with some white color (if you do the above experiment with white on white, there’s no problems.)
Another interesting trait–this only happens if the object being blurred has sharp edges–ie., the transparency goes from 0% to 100% with no in-between transparencies. So if you barely feather or blur the edges of the object with a minute amount of, say, Gaussian blur (0.2 pixel), then apply the lens blur, the halo problem doesn’t occur.
Bart
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