unsharpen mask

[carrbowl]

can someone explain to me in laymens terms what the 3 things under the USM do?? Amount, radius and threshold....and why would you use the USM more than once on a photo?? why not just adjust it once?? Are you just doing a little at a time until you get the look you are going for???

[Daniel Bates]

This website explains it better than I ever could:

http://www.luminous-landscape.com/tu...ding-usm.shtml

The reason I use two iterations of USM is because the first is to sharpen edges, and the second is to add general contrast (the low amount percentage and high radius 'pops' the contrast nicely). That particular technique is called Local Contrast Enhancement (LCE) - the article mentions it as well.

[carrbowl]

well you are just full of usefull information tonight....do you always sit around waiting to help us non knowledgeable types out??? or are you just bored???? I wish I had enough information in my brain I could actually share!!!!

[Daniel Bates]

It's my job! Besides, I won't have any time to do it for the next few months, so I'm getting my last fix of TPF for a while.

[Duffy Pratt]

The three functions -- not in order:

Radius -- controls the size of the halos that will be created. It is how large the blurring effect that creates the radius will extend. The larger the radius, the bigger the halo (blur).

Threshold -- controls the number of pixels that have to vary before the mask takes effect. A low threshold tells the filter to sharpen everywhere. A high threshold will limit the sharpening to areas where there are larger distinctions. This is mostly useful when you want to avoid sharpening some noise in your picture. You might be able to achieve what you want by raising the threshold.

Amount -- says how much of a sharpening effect you want. The more the amount, the greater effect the sharpening will have. To see what this means, its probably best to play with the slider.

There are several types of multi-pass sharpening. Sometimes you might want to do a "capture" sharpening at the beginning, and then an "output" sharpen before printing. This process forms the basis of Bruce Fraser's book on sharpening, which is excellent. Sometimes you might want to do high radius, low amount sharpening before doing traditional sharpening, as Daniel points out. Sometimes you might want to do sharpening on different channels -- like on the K and C channels in a portrait in CMYK. And recently, I've been sharpening on two separate layers, one set to Darken and the other to Lighten mode. This lets you separately adjust the light and dark halos that are created. Thus you can temper the annoying light halos that are created by leafy trees, for example, without losing the good sharpening that comes from the dark halos.

Hope this helps,

Duffy

[KdLaneJr]

Here is more information than you want to know about Unsharp Mask.

Yes, I was actually researching it earlier this evening after seeing Daniel's "heavy handed" use of unsharp mask.

The Russel Brown show also has a quicktime movie that covers the use of smart sharpening. Something else that it good to know.

Not trying to give you knowledge overload. Sometimes reading and seeing it explained several different ways helps to understand the process.

Ken

[johnastovall]

The source book on Sharpening:

Real World Image Sharpening with Adobe Photoshop CS2: Industrial-Strength Production Techniques
by Bruce Fraser

Made a believer out of me about the need for two pass sharpening and a owner of PhotoKit Sharpener.

[carrbowl]

Thanks for all the information...and yes I need several translations...!!!! I do not read and understand well..I need to be shown...so reading several different ways usually helps. Thanks so much.

[KdLaneJr]

If you're working with LR, Here is another good place to look and the information should crossover to CS2/CS3 to a large degree. Moreso to CS3.

Ken

[KdLaneJr]

I've downloaded the trial version of PhotoKit Sharpener. Have not installed it yet.

Was put onto this link. at POTN. The general concensus there is that this is an excellent sharpening toolkit..., and it's free. (well unless you like it so much that you make a paypal donation.)

Ken