graphiteBP's blog

Sharpen / Unsharpen

posted by graphiteBP, Jan 5, 2006 6:31 AM — 7 comments

This article which resides on a blog written by Cameron Moll, I found attempts to demystify the fundamental difference between Sharpen and Unsharpen in Photoshop.

The link is: http://www.cameronmoll.com/archives/000169.html , and is titled, "Please, sweat the small stuff".

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1. posted by teambo, Jan 5, 2006 4:44 PM

That's actually not a very good tutorial.

Applying very high values of Unsharp Mask tends to cause a lot of edge enhancement in an image and will increase graininess. Worst of all, unsharp mask tends to deteriorate color quality at the edges - this is especially a problem if your camera isn't the best with color accuracy.

But, the good news is that you can get around that problem.

What you need to do before you use Unsharp Mask is convert the image to Lab Color in Photoshop. Then, in the Channels, select only the Lightness channel.

Your image will now appear in black and white. This is because you're only working on the lights and darks of the image, not the color. Apply the Unsharp Mask on this channel ONLY. Settings I was told to use is a % between 40-85, a radius of 0.8 pixels, and a threshold of 1 level. (This I learned from a professional photographer who did work for AP.)

Sorry I'm not using a lot of "technical" terms but I'm an amateur photographer at best. I'm much better at Photoshop. :P


2. posted by graphiteBP, Jan 5, 2006 8:07 PM

Cool suggestion. Thanks. I will have to try that method you prescribed.

There is another method that I use that always gets me a rejected image when submitting for stock photos, but effective for personal use to sharpen and enhance some blurry pictures.

I do the following:
-duplicate the background layer
-change the blend mode for the duplicated layer to 'overlay' (50% - 75%) opacity strength
-apply 'high pass' filter by pixel value to your personal taste of sharpening or contrast, depending on the size of the photo

To try different strengths of this effect, you can change the level of opacity in the duplicated (affected)layer


3. posted by csp, Jan 24, 2006 4:54 AM

To avoid colour damage when using unsharp mask on RGB images:

First, do your sharpening, then go Edit>Fade Unsharp Mask, change the mode to 'Luminosity' (it's the equivalent of using the Lightness channel in Lab colour - except you don't have to change colour spaces) and fade till you get the desired strength of the unsharp mask. No colour degradation.


4. posted by csp, Jan 24, 2006 5:00 AM

Oh, as graphiteBP has written, when you apply the high pass filter it generates some colour details which might affect your overall colour as well.

What I do is desaturate the overlay channel:

Image > Adjustements > Hue/Saturation - set Saturation to -100

Then go Edit>Fade Hue/Saturation and change the mode to 'Color' (this way you wont affect the luminosity of the overlay).


5. posted by divyesh, Jan 28, 2006 8:46 PM

nice suggetion


from dvs......


6. posted by amoreluca, Apr 9, 2009 3:56 PM

bravo


7. posted by escan, Aug 19, 2010 11:33 AM

Thanks!!!

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