[펌] RGB Sharpening: Dan Margulis latest

http://forums.dpreview.com/forums/read.asp?forum=1021&message=24980642
RGB Sharpening: Dan Margulis latest.
User: My Threads Flat view
Navigation: ^ Forum |< First < Previous Next > Next New >>
Forum Nikon D3/D2/D1
Subject RGB Sharpening: Dan Margulis latest.
Posted by Iliah Borg [CLICK FOR PROFILE]
Date/Time 9:04:52 PM, Wednesday, September 26, 2007 (GMT)
"...I wanted to throw out a sharpening idea that I've been having success with recently. I am intending to show this in my advanced classes later this year but haven't tested it as well as I should have with enough of a variety of images. So, to those interested in testing it, suggestions or comments would be welcome...
For the moment, this idea pertains only to conventional sharpening, meaning with a high Amount and a relatively low Radius. I have had only mixed success with hiraloam. Although it is mildly applicable in CMYK and somewhat more in LAB, its real power would be for those forced to sharpen conventionally in RGB, which is technically the weakest sharpening space for several reasons.
We all know that conventional sharpening is highly effective at adding focus, but also prone to adding undesirable detritus, particularly in lighter areas. Consequently, there have been many ideas about sharpening through a mask. John Ruttenberg has suggested using Blend If sliders to limit the amount of sharpening that can take place in lighter areas. I have suggested using Command-Option-1, then Command-I, to load an inverted luminosity mask and sharpening through that. And many people have mentioned some type of edge mask that tries to select only the areas of transition, and sharpening through that. I have never been a big fan of this method because it seems to me to yield unnatural results. The first two methods OTOH are relatively safe but don't always allow as much sharpening as I would like.
I wrote about why darker areas accept sharpening better than lighter ones as early as 1994. Since then, I've realized a corollary--in addition to lightness, a strong color is an argument against sharpening. We don't like to oversharpen skies, the petals of flowers, and human skin, for example. Inverted luminosity masks don't take account of this effect. A deep red rose is a fairly dark object, so an inverted luminosity mask would allow a lot of sharpening, which we probably don't want. More neutral objects OTOH accept heavy conventional sharpening much more gracefully, and not just on their edges.
My suggestion is a mask that caters to both--that allows more sharpening where the image is darker but also restricts it where the image is colorful. While it is possible to make a convoluted Action that generates such a mask by a series of blends of the RGB channels, there's a faster way--make a false separation, and use an inverted Heavy GCR black as the mask for the RGB sharpening."
I coded the method into an action you can download from http://www.pochtar.com/DM_RGB_SharpenAction.zip
The radius of USM can be between 0.7 and 2.0 (Dan recommends to start with 1.2); depending on the structure of the image.
Moving the middle slider in the Levels dialogue controls the effect of sharpening.
Another control is "Blend If" sliders in upper layer "Blending Options". It allows to exclude extreme highlights and shadows from sharpening.
Please provide your feedback and suggestions as Dan requested.
--
no text

DM_RGB_SharpenAction.zip

by shotgunlee | 2007/09/29 15:00 | 디지털카메라 관련 | 트랙백 | 덧글(0)

트랙백 주소 : http://shotgunlee.egloos.com/tb/2189626
☞ 내 이글루에 이 글과 관련된 글 쓰기 (트랙백 보내기) [도움말]

:         :

:

비공개 덧글

◀ 이전 페이지다음 페이지 ▶