Philip Rhoades writes:
> What still doesn't make sense is that if the original file is JPG and
> one simply opens it and then saves it as another JPG file with 100%
Because JPEG isn't meant to be saved at 100% quality.
The JPEG FAQ, http://www.faqs.org/faqs/jpeg-faq/part1/section-5.html, says:
Except for experimental purposes, never go above about Q 95; using Q 100
will produce a file two or three times as large as Q 95, but of hardly any
better quality. Q 100 is a mathematical limit rather than a useful setting.
If you see a file made with Q 100, it's a pretty sure sign that the maker
didn't know what he/she was doing.
Do a web search on
jpeg quality "100%"
and you'll find lots of detailed discussions of this.
GIMP's "Show preview in image window" check box is extremely
helpful, and lets you see the trade-off in quality versus size.
It's too bad it's not enabled by default.
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