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Reducing Images - best practice?
Just wondering what other folks do to get the best possible results
when *reducing* images - mainly, but not solely, for web use... For me, I've found that bicubic is definitely *not* the way to go on many images, due to added 'artefacts'. I use Thumbs Plus and Irfanview most often for reducing, and I have found that either TP's simple 'resampling' routine, or IV's Lanczos, give much better results than the other methods, especially on slanting lines/fine details (I hate jaggies!!!). But it depends on the image content (I'm not sure yet exactly what the criteria are, but I'm working on it..). I don't generally use steps for reducing, as I can't see any advantage - anyone else? Once I have a good looking un-artefacted image, I use PS USM with a small radius - maybe 0.3 to 0.8, about 100% to 200%, and levels at around 3-7. Again, these vary depending on image content. I just play until it looks right.. There's a very good page on this on Bart vdW's site: http://www.xs4all.nl/~bvdwolf/main/f...e/example1.htm Comments and alternative methods welcomed.. (Crossposted to aus.photo and rec.photo.digital, hope no-one objects - if you do, just remove the cross-...) |
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Reducing Images - best practice?
On Mar 16, 6:39 am, wrote:
Just wondering what other folks do to get the best possible results when *reducing* images - mainly, but not solely, for web use... For me, I've found that bicubic is definitely *not* the way to go on many images, due to added 'artefacts'. I use Thumbs Plus and Irfanview most often for reducing, and I have found that either TP's simple 'resampling' routine, or IV's Lanczos, give much better results than the other methods, especially on slanting lines/fine details (I hate jaggies!!!). But it depends on the image content (I'm not sure yet exactly what the criteria are, but I'm working on it..). I don't generally use steps for reducing, as I can't see any advantage - anyone else? Once I have a good looking un-artefacted image, I use PS USM with a small radius - maybe 0.3 to 0.8, about 100% to 200%, and levels at around 3-7. Again, these vary depending on image content. I just play until it looks right.. There's a very good page on this on Bart vdW's site:http://www.xs4all.nl/~bvdwolf/main/f...e/example1.htm Comments and alternative methods welcomed.. (Crossposted to aus.photo and rec.photo.digital, hope no-one objects - if you do, just remove the cross-...) This may depend somewhat on the specific photo editor. I use PSP, and have found the bicubic very good in general. However, PSP has an option called "smar t size", and I have no idea which algorithm or algorithms it uses. I get the idea it depends on the amount of the resize job and selects what it thinks is the best algorithm for that job. I ordinarily cop out and just go with that, but when for some reason I HAVE used PSP's bicubic have been quite satisfied |
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Reducing Images - best practice?
"Don Stauffer in Minnesota" wrote in message oups.com... On Mar 16, 6:39 am, wrote: Just wondering what other folks do to get the best possible results when *reducing* images - mainly, but not solely, for web use... SNIP There's a very good page on this on Bart vdW's site: http://www.xs4all.nl/~bvdwolf/main/f...e/example1.htm This may depend somewhat on the specific photo editor. I use PSP, and have found the bicubic very good in general. However, PSP has an option called "smar t size", and I have no idea which algorithm or algorithms it uses. If you want to be sure it does a proper job for a given subject, try the link on my other webpage article on downsampling: http://www.xs4all.nl/~bvdwolf/main/foto/down_sample/down_sample.htm which also allow to compare to several other properly prefiltered ImageMagick methods. The 'Rings1.gif' zone-plate target has image detail at any angle and with virtually all spatial frequencies that can be represented in an image of that size. I made that page is specifically because of the increasing need to down-sample multi-megapixel images (from high resolution film scans or capable digicams) e.g. for web publishing. It gives guidance, especially if one wants to batch process many images without the need to inspect each and every image for artifacts. If the down-sampled target is well behaved, normal images (even the tricky ones) can't be worse than that extremely critical target. -- Bart |
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