Re: JPEG
Re: JPEG
- Subject: Re: JPEG
- From: Gary Smith <email@hidden>
- Date: Mon, 8 Jul 2002 21:56:45 -0600
Hi Anthony, did you notice how the subject of your original question
about JPEGs changed from your topic to the Photoshop 7 CMYK JPEG bug
issue?
I heard back from the instructor. To sum up his reply choosing Save
As... a copy re JPEGs a file and just using Save or closing and
saving does not. I tested like this:
1. Created an RGB document 2400 pixels x 1700 pixels. Used highly
saturated colors and a Layer Style of Pattern Overlay to add some
noise and Saved as... psd with the layer intact then closed all files.
2. Duplicated it in the Finder and named it "One"
3. Opened it and added some type on the right half. One word. Then flattened.
4. Saved it as JPEG with a quality of 4.
5. Opened the image and verified the introduction of apparent JPEG artifacts.
6. Copied the upper left corner.
7. Added more type then flattened.
8. Closed and saved changes on the way out.
9. Reopened and repeated the process 10 times.
10 Opened the file and pasted the original upper left corner and
toggled the visibility on the corner layer.
It was apparent that there was no change or further degradation to
the image after 10 saves.
I then set about carrying out the process again, except I Saved as...
a copy each time with a new name and quality of 4, opened the new
file and repeated 5 times.
Again, I wasn't noticing any further image degradation - until I
changed the quality setting from 4 to 7, closed then reopened. NOW I
saw an instant degradation in the image quality. It was quite obvious
that re-JPEGing a JPEG had occurred.
So it seems to me not to be an issue of Save versus Save As... but
rather a change in the quality setting causing the re-JPEGing a JPEG
event with the expected destruction of the image!
Gary Smith
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