Quoting BB: It seems to be a particular case for which JPEG is very weak.

You mean... for which Photoshop is weak. Not JPG as such. I guess/hope the Photoshop way of saving JPGs has strong points too, but for smooth color gradients it creates apparent limunosity banding which increases with repeated load/save cycles. It might have similar issues in other kinds of images, but I guess these are far less visible.

Photoshop does not have a problem in the color-part, and other programs like PaintshopPro don't have the luminosity-issue either (or at least far less).

But please note: Photoshop is intended for professional use, and this use advices to turn an image into JPG when it's required as the last step in (internet) publishing. A one-off thing. So in fact we're debating on a flaw in a solution for which we shouldn't have the problem in the first place.

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though