To continue on the same topic of yesterday I’d like to mention a new function in PS CS. In the Image/Image size menu point under Resample image there are two new options. Bicubic smoother is an enhanced algorithm which should be used to upscale and Bicubic sharper should be used to downscale images. They produce a slightly better final image than any of the other 3 options that were previously available before CS.
However you achieve an even better quality for upscaling images using the so called Stair interpolation. What you basically do is just do the image enlargement in steps of 10%. More detail of the image will be kept using this technique, but obviously the time to process your image will increase. You can help that by scripting the operation. I’ve created a simple script that you can download. Load it into your actions pallette and just press Apple-F1 to run it. Each time you execute the script your image will be upscaled by 110%.
After upscaling an image you should try to use the Filter/Sharpen/Unsharp mask to bring back some edges that has been lost when blowing up the image. Alternatively if you don’t like the effect that this filter does to your colors at the edges you can run the same filter only on the Black channel once you converted your image to CMYK.
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