# Unsharp Mask



## 036 (Feb 27, 2003)

Any advice on the use of this tool in Gimp?

Before:










After a little touch of unsharp mask:










Hard to pin down exactly what it does but it does seem better overall.

Si


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## Fred (Feb 23, 2003)

No idea,but i love that watch,fred


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## Stan (Aug 7, 2003)

USM seems to work like "actuance" developers used in black and white developing. It appears to sharpen edges and not blocks of tones. I use it on pictures I've reduced in size because they lose some sharpness but I try to keep the radius to less than 0.8.

Good tool, and a very nice watch.


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## 036 (Feb 27, 2003)

Thanks Fred - here's a few more pics of the watch. Incidentally it is a great timekeeper and the hands line up well etc - which is fortunate as it would be a bit of a mess if they didn't.

Hi Stan: what settings do you use for threshold and any other parameters for unsharp mask?

BTW I have not used any filters etc on these ones:


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## Stan (Aug 7, 2003)

Hello Si,

I fiddled with Clipping and Strength in PSP and found it best to only modify Radius as it has the most obvious effect in PSP. That might produce a different result in PhotoShop, but, I doubt it.

From my humble observation, Radius has the most "notable" effect when using USM.


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## ESL (Jan 27, 2004)

In my opinion, the after shot looks a bit over "processed". USM is a nice tool but needs a bit of tweaking to get the best out of it, and it does indeed enhance edges to achieve its effect, and it uses contrast adjustments to "edge pixels" to do it.

I normally use Photoshop but the principles should be the same with any software with USM. There are three settings (in photoshop): Amount, Radius and Threshold

*Amount *sets the amount of contrast there is to be, between pixels that are at edges and those that are not. If required for hi-res printed images, somewhere between 150 and 200% is a good place to start. With very high resolution images (i.e.lots of pixels) larger percentages may be required, experiment.

*Radius *is used to determine the number of pixels surrounding the edge, to be sharpened. The larger the number, the more pixels are calculated as being either side of "the edge", so they will have their contrast increased as well. If too high a radius is set, edges will start to look too thick or over defined, or the whole image (if full of edges) will become too contrasty. A Radius between 1 and 2 is recommended (in photoshop). A lower value sharpens only the edge pixels, whereas a higher value sharpens a wider band of pixels. It is also useful to note that this effect is much less noticeable in print than on-screen, because a 2-pixel radius represents a smaller area in a high-resolution printed image

*Threshold *is used to determine how different (in contrast) a pixel must be from the next one, before it is considered an edge pixel. For example, flesh tones will be very close in colour to one another, so no edges will normally be detected on flat skin. A value of 0 (zero) normally causes ALL pixels in the image to be sharpened. Try values between 2 and 20 and use the preview function(if you have one) to see the effect.

A good trick I use, is not to apply all the sharpening in one hit, which can look a bit "over processed". Try setting lower values but apply the filter two or even three or more time passes, till you get the effect you want.

Lovely Certina by the way.


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## Stan (Aug 7, 2003)

I haven't used Potoshop even though I was given a pirate copy.









George,

Thanks for that, I don't have a clue what the adjustments do.







I just use my eyes to get the most subtle effect. One thing I think is worth noting, it is best to do all adjustments before saving a picture (or so I'm told). Every time a losey format like Jpg, et al, is saved it recompresses and reduces image quality. Multiple saves are supposed to be a bad thing.

I don't know if this is true but it seems to be.


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## ESL (Jan 27, 2004)

Hi Stan,

One of the benefits of Photoshop, and probably other "high-end" programs, is that you have more control over what happens. I think you are probably right about multiple saves in PSP, but in Photoshop, it will save in the original compression factor; It will only compress again if you ask it to.

The problem with photoshop (for me anyway) is that it is huge!!! I seem to have been using it for yonks and still don't really understand all of the features.


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## 036 (Feb 27, 2003)

Thanks for those tips George - I will try again when I have time. You are right, I think - the second one does look wrong, too harsh or cold perhaps.

I think with many vintage watches it is better to go for a slightly "warmer"look at the expense of some detail.

Probably better to look at my technique first rather than the after-processing...

Re Photoshop Elements 3 - it definitely seems to be the pick of the bunch, but unfortunately it does not work with 98SE. Elemnts 2 does but does not have a lot of the desirable new features.

I like Gimp but find it difficult to get the plug-ins to work (I have no knowlege of computer languages / compilers etc).

Simon


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