Sharpening luminance

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greenmorpher
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Post by greenmorpher » Fri 16 Nov 2007 01:24

Hiya Loadus

Excellent result. Can you clarify what you actually did -- step by step? I'm trying to learn PL32 and general raster techniques at the same time! :P

What exactly do you mean :clarified with an overlay layer". The unsharp mask I get. (I think! :o )

Cheers, Geoff

Geoffrey Heard, Business Writer & Publisher

"Type & Layout: Are you communicating or just making pretty shapes" -- Revealed! The secrets of how you can use type and layout to turbocharge your messages in print. See the book at http://www.worsleypress.com

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Loadus
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Post by Loadus » Fri 16 Nov 2007 18:37

greenmorpher wrote:What exactly do you mean :clarified with an overlay layer"
Hiya.

You can try it like this:

1. Duplicate the original image into a layer, set the blend mode to Overlay
2. Make the layer grayscale
3. Invert the layer, ie. make it negative
4. Take gaussian blur and apply it to the layer - I used radius 20 for the owl pic.
5. Adjust the strenght of the effect with Opacity
6. I used Unsharp Mask as the final sharpen effect with radius 1.2 and strenght of 300% (but I did that in linear space, so the effect is somewhat different from normal sRGB editing)

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greenmorpher
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Post by greenmorpher » Fri 16 Nov 2007 20:48

Linear space???

Cheers, geoff

lutz
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Post by lutz » Fri 16 Nov 2007 21:59

Thanks Loadus,

this is indeed a very neat technique! Does this approach have a name?


Geoffrey,
there a two image editors that I know of, Lightzone and Helicon Filter, that perform most adjustments in linear color space ( in contrast to the standard gamma adjusted space) because theoretically there is less information loss in the highlights and shadows ( these parts of the image become compressed in the gamma curved color space and the midtones expanded). These editors have to convert the images at the end back to a gamma adjusted space to conform with the expectations of human vision. I have no clue if my terminology is correct here.
Last edited by lutz on Mon 19 Nov 2007 10:32, edited 1 time in total.

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Loadus
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Post by Loadus » Sat 17 Nov 2007 15:19

lutz wrote:Thanks Loadus,

this is indeed a very neat technique! Does this approach have a name?
Cool. It might be called contrast masking, but I'm not sure - it's sort of fast tonemapping.