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02-15-2010, 03:12 PM   #16
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QuoteOriginally posted by Mike Cash Quote
I'm not entirely sure I'm grokking you correctly. Are you saying that straightening a crooked photo is destructive? I'd rather dent a few electrons than have noticeably and distractingly crooked photos. And I almost always shoot in RAW, by the way.
I think he is saying that you lose part of your photo when you straighten -- have to crop some of the edges out. Still, I agree with you, I would rather crop a little and have a nonirritating photo then, let it go just so I can keep the edges intact.

02-15-2010, 04:29 PM   #17
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QuoteOriginally posted by Mike Cash Quote
I'm not entirely sure I'm grokking you correctly. Are you saying that straightening a crooked photo is destructive? I'd rather dent a few electrons than have noticeably and distractingly crooked photos. And I almost always shoot in RAW, by the way.
Sure. It's like applying a mild blur filter all across your image.

Is it a reall problem? Open to debate, but it's definitely not in line with the "don't use UV filters, shoot RAW, save in 16-bit prophoto RGB TIFF, never save in JPEG even once (let alone twice!), technical image quality is everything" pixel-peeping mindset. (I suppose that in that case the "right" thing to do is leave the image crooked and then cut your final print so it's straight.)

If rotating the image doesn't bother you yet you feel attached to some of the above, you might want to reconsider priorities.
02-16-2010, 03:27 AM   #18
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That's right. Anything you do to a Jpeg is destructive to the image. Even just a simple rotation from Landscape to portrait and then saving. But not if the image is RAW and you edit that way saving the final edited version to a Jpeg.
02-16-2010, 06:42 AM   #19
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QuoteOriginally posted by Peter Zack Quote
That's right. Anything you do to a Jpeg is destructive to the image. Even just a simple rotation from Landscape to portrait and then saving. But not if the image is RAW and you edit that way saving the final edited version to a Jpeg.
Wow, that's wrong in three ways! (EDIT: okay, two and a half. )

1) 90/180/270 rotations to JPEG files can be done absolutely losslessly with a simple transform. However, it's true that if you do it within most image editors it won't be done without recompression. Use a tool which explicitly says it can do lossless JPEG rotation — if you're not sure, try jhead.

2) if you rotate your RAW image at anything other than the "square" angles, it certainly does cause the loss I described before. (EDIT: obviously not to the original file unless you delete or overwrite that; sorry, I missed what you were saying on first read.)

3) And finally, saving your RAW to a final edited JPEG is of course a lossy step too. (But I suspect in many cases causing less visible image degradation than #2.)

02-16-2010, 06:56 AM   #20
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When I first read this I was surprised as well But Scott Kelby mentioned it in a book I have. Then I found the same thing on an Adobe training site. Opening a Jpeg in an editor and even a simple rotation then saving the file downgrades the file.

But if you edit a RAW file, rotate it and save the file as a Jpeg. You of course are not effecting the RAW and the resulting Jpeg is from the original RAW.If you edit from the Jpeg after that and save, then you will degrade the image with each edit or save.
02-16-2010, 07:05 AM   #21
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I should note, I'm speaking about Photoshop products. There are lossless Jpeg editors found on this list for cropping and image rotation:
Lossless jpegtran applications

Background: http://bermangraphics.com/coolpix/jpgrotate.htm
02-16-2010, 02:42 PM   #22
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Sorry for the argumentative tone above, by the way. Hadn't had morning coffee.

I haven't tried a double-blind study, but I'd be willing to bet a small sum that

A) taking a high-quality JPEG file, rotating 90, and re-saving as a new high-quality JPEG

results in less loss of detail and fewer added artifacts than

B) taking a RAW file, rotating 3, and saving as high-quality JPEG.
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