t ko,
JPEG-2000, which uses wavelet-based compression, is much better than DCT-based JPEG for high compression ratios. For a comparison, see:
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http://www.luratech.com/>
Hopefully the soon-to-be-released Photoshop 8 will have full support for JPEG-2000. Even more hopefully, Adobe’s implementation will include support for regional compression, allowing you to select which regions should have higher quality and which regions should have higher compression. LuraTech’s LuraWave plug-in for Photoshop has had that capability for years, although I haven’t seen anything to indicate that their JPEG-2000 plugin for Photoshop does.
Pegasus Imaging’s JPEG Wizard v2 standalone program does have Regional Compression capability for regular DCT-based JPEG files:
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http://www.pegasusimaging.com/jpegwizard.htm>
Apparently their JPEG-2000 plug-in for Photoshop does not support regional compression:
<
http://www.pegasusimaging.com/imagepressj2k.htm>
Let’s hope that Adobe’s JPEG-2000 implementation in Photoshop 8 does support regional compression. But, even without regional compression, JPEG-2000 can solve your problem by giving you much better image quality at high compression ratios. JPEG-2000 JP2 browser plugins are freely available.
If you wish to stay with the "old fashioned" DCT-based JPEG, JPEG Wizard v2 might do the trick for you or, even simpler, follow Hot_Denim’s advice to use variable compression (regional compression) in Photoshop.
— Burton — (not associated with LuraTech or Pegasus Imaging)
