RE: [PRODIG] PS7 .jpeg resave

[Douglas Burns]

On 2/12/02 Martin Evening wrote:


>>OK, try this test. Take an image save it as a JPEG using a low-medium
setting. Copy this first version and keep it located in a separate
folder. Now reopen and record an action that resaves the first  image
using the same JPEG setting and closes the file. Keep reopening and
applying the action - say, ten times or so. Now open the first version
drag the 10x resaved JPEG image as a new, registered layer (hold down
the shift key as you drag one window the other with the move tool) and
then set the new layer to difference mode.<<

>>In difference mode, any differences between one layer and the other
will show up as image detail. If the difference is slight, you may have
to add a major levels or curves adjustment layer to the top of the
layer stack. Do the results surprise you?<<

I've just tried this from PS6 and the results do surprise me! I can see not
a single difference between the two images; the file sizes are identical
too.

This doesn't make sense to me, but I've tried the exercise twice and get the
same result. Is this a bug in PS or is it supposed to happen (or have I
screwed up the exercise?)

Douglas

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