Author Topic: JPEG Conversion causing isolation issues (Read 6244 times)

djpadavona · « **on:** August 19, 2010, 13:16 »

I'm running into a common iStock rejection with isolations having stray areas, etc.

I've gone back and looked at the Photoshop PSD files, and the JPG files, and I am seeing the same problem time and again. The PSD file at 16 bits has a perfect isolation. Clicking on the magic wand tool with 1 Tolerance draws a perfect path around the object.

However once I convert to 8 bit and save as a JPG (Normal encoding, 12 max quality), there are stray areas in the isolation.

This is particularly frustrating because this is obviously being caused by the 8-bit JPG conversion which iStock requires. Anyone have a way around this? Because right now I don't see a reason to do anymore isolations if the imperfections of the JPG format are going to continue messing up my images.

donding · « **Reply #1 on:** August 19, 2010, 13:22 »

I don't know if you shoot in Raw or not but you do have the option to open as a 8 bit. Maybe if you do that to begin with you won't have a problem with the conversion. Just a suggestion...

kiwistock · « **Reply #2 on:** August 19, 2010, 13:29 »

It's not the 8 bit conversion that does this, it's an artefact of JPEG lossy compression. Every isolation shows this in JPEGs, and it's not what they're complaining about.

Finding out what they really mean is another matter...

Sean Locke Photography · « **Reply #3 on:** August 19, 2010, 13:39 »

Right. There are probably other issues. The little bits of non white that appear should be expected. Post an image for more comments.

djpadavona · « **Reply #4 on:** August 19, 2010, 13:45 »

Thanks. That answers my question, that my technique sucked but Photoshop did its job. Which is far less frustrating as I can fix my technique.

madelaide · « **Reply #5 on:** August 19, 2010, 18:01 »

I had this problem too, I think it was in StockXpert. The original TIFF was perfectly white, then the JPEG, even at a small compression, showed a few stray pixels.

FD · « **Reply #6 on:** August 19, 2010, 18:24 »

This is a well known phenomenon. Read here and scroll down halfway.

FD · « **Reply #7 on:** August 19, 2010, 19:07 »

Quote from: madelaide on August 19, 2010, 18:01

I had this problem too, I think it was in StockXpert. The original TIFF was perfectly white, then the JPEG, even at a small compression, showed a few stray pixels.

That happens when you don't fill up the white selection at 16 bit with pure white (PS: shift-F5 > white).

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Author Topic: JPEG Conversion causing isolation issues (Read 6244 times)

djpadavona

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madelaide

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