[filmscanners] Re: JPEG Lossless mirror?

["Pat Cullinan, jr." <pcullinan@mindspring.com>]

Mark Otway wrote:

> >> This isn't so, Mark.  While you're editing an image is PS,
> >> no jpeg processing is performed. Your'e perfectly safe.  The
> >> jpeg processing occurs only when you save the image to a jpg
> >> file, and even then virtually no further degradation takes
> >> place, believe it or not (you can test this yourself).
>
> I know the encoding only takes place when the image is saved in PS (as
> opposed to when it's manipulated). But since the act of re-encoding
> results in some data loss, if I can perform these simple tranformations
> (flip) without doing so then it's obviously preferable.

Hi Mark,

Oh, I get it.  All the same, if the act of re-encoding results in data loss,
I've never noticed it. I've taken a jpeg image and subjected it to 20 edits
and re-encodings, and was unable to detect any image degradation.
It's kind of counteintuitive, but you can try it for yourself.

I had been a believer in the proposition that multiple jpeg saves would
degrade an image, but after reading a notice to the contrary in one of the
trade mags, I did my own trials and now I save and resave jpegs which
aren't even maximum quality without any qualms.

Thanks for raising the issue.  I'm exploring Guido's Tech Site.  It's a good 
turn-on.


>
>
> Mark
>

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