unsharp mask

metroshane · Mar 9, 2004

Can someone please explain masks (especially the unsharp mask I hear so much about). I'm pretty smart, just ignorant...so get as technical as you want.

voodoocat · Mar 9, 2004

Hey Shane, I was just planning on adding unsharp mask to the tips section this evening. The best way to do it is to switch to lab mode (image > mode > lab) then on the channels tab select lightness and apply the unsharp mask. For prints I use between 100-150%. Then you can switch back to RGB mode.

Osmer_Toby · Mar 9, 2004

is it really necessary to go to lab? i sharpen in rgb; is there some advantage to converting and sharpening just the lightness channel of luminosity?
also, unsharp mask is kinda misleading- it's found in the filter section...

voodoocat · Mar 9, 2004

Osmer_Toby said:
is it really necessary to go to lab? i sharpen in rgb; is there some advantage to converting and sharpening just the lightness channel of luminosity?
also, unsharp mask is kinda misleading- it's found in the filter section...

Yes, it yields better results. That way you aren't messing with the color information in the image.

vonnagy · Mar 9, 2004

Yes, it yields better results. That way you aren't messing with the color information in the image.

voodoo, we humbly bow before thy great wisdom. I've learned something new again!

voodoocat · Mar 9, 2004

Ok, the tutorial is complete. You can see the difference between sharpening in Lab vs RGB mode

vonnagy · Mar 10, 2004

voo, thats an excellent tutorial.. but the final results i am not sure why you blew up the final comparison, i am have a hard time distinguish the difference between the two :scratch:

however, when i went and tried the lab thingy on one of my photos and the results were amazin! Thats one of the best darn tips i've learned in while!

voodoocat · Mar 10, 2004

I blew it up because you can see the difference in the noise on the samples. The one done in RGB mode has a lot of stray color pixels, the one done in Lab mode does not.

Digital Matt · Mar 15, 2004

Thanks for the lab tip. Here's another. You can use the unsharp mask to add contrast to a photo as well. Using a setting like 20%, 50, 0 will add a subtle contrast boost to your image, and then you can run your normal unsharp mask setting afterwards. I normally use 500%, 0.2, 0, or 300%, 0.3, 0.

I got this tip from the Luminous Landscape. Here's a link to the article.

http://www.luminous-landscape.com/tutorials/contrast-enhancement.shtml