First post in here!

[TrinityOfOne]

OK, probably a real dumb question but what gets altered in a PSD to warrant having to save changes when you use Save for Web?

[Scott]

When you use the save for web it makes a composite of what's visible and uses that for the save for web. I believ eit stores that composite as a thumbnail and icon for the image... that's all.

[TrinityOfOne]

Ahh, thanks Jolt, it's just been niggling at me for a while now.

[TinCupid]

[QUOTE=TrinityOfOne]Ahh, thanks Jolt, it's just been niggling at me for a while now.[/QUOTE]
Not to discredit Jolt bit maybe to add to his explanation, "Save for Web" saves the image to 72 DPI, the optimum vewing quality for web pages, thus reducing the overall size to a quickly loading image.

[Scott]

Yeah but if you have an image.. any image.. and it's already saved, sitting on your hard drive. if you----

Open it
File > save for web
Save in the save for web dialog
then close the image

Photoshop asks you if you want to save the image when you try to close it. You've technically not done anything to the image. But Photoshop wants to save it. It does that because it's updating thumbnail and icon information.

[TinCupid]

Aha... I see. Thanks

[claven]

but what gets me is that a flat 72 dpi rgb file, saved as jpeg at max quality, will STILL decrease in size if "saved for web" at highest quality???

I'm just guessing, but i always thought "s.f.w." offered advanced optimizing capabilities???

[TrinityOfOne]

The only thing I can think of, is unchecking the 'Optimise' option