new user: OK to run an image through multiple runs of -sharp

[bookpub1]

After some tips from this (great) list I got -sharpen to give me great results on 180+ images (run at 6x3 ... I'm told a sigma of 3 is quite a lot of sharpening).

New question-- is it safe to use the sharpen tool a second time on the the same images? I'm not totally sure what I mean by 'safe' -- are there any downsides, is there a danger of losing legibility, whatever.

Intuitively I'm thinking that since running sharpen helped so much once then a second pass might help even more (tho probably less of an improvement than I got on the first run)... but is this correct?

Thanks in advance!

[bookpub1]

Original post said -sharp , but I meant -unsharp

[difference between the two, and what images to use each one on, are still not clear to me... confusing!]

[anthony]

If you over sharpen images you get edging halo type effects as the edges become over sharp. Better to alwasy return to the original image if posible.

That is not to say you can't do it!

PS: -unsharp has more control than -sharp

[bookpub1]

Ok, thanks for the warning about halo effects... I'll give it a try, but carefully. I can't go back to the original image... I already used -unsharp at sigma=3 and I still need to enhance legibility!

Again, thank you for this great site!

[anthony]

Some sharpening effects are discussed in...
http://www.xs4all.nl/~bvdwolf/main/foto ... ample1.htm
Where they are shrinking an image using various programs, and trying to sharpen the results of some of those programs.