Keep Raw/jpg Conversion?

[newb2pro_1day_or_so]

I was told a couple of days ago that a jpeg will lose color and sharpness as the file is opened more times. I'm wondering if I should process the RAW file in Photoshop and then convert to jpg as needed for prints or is the color loss and such not noticable in jpeg? I don't even know if this is right, it's just something I heard and wanted to see if what I was doing was the wrong or right way to do it. I take the raw and process it slightly, convert to jpeg and do most if not all my processing in CS2. I do keep some RAW images if I really like the picture and think it has a high potential.

[gcogger]

JPEGs deteriorate if they are saved multiple times. You can open them as many times as you like and it will have absolutely zero effect on the file.

If you want the absolute best quality, save the converted file in a lossless format (e.g. TIFF or PSD) until all editing is done, then save as a high quality JPEG if you want to save space. This also has the benefit that you can do all your edits in 16 bits per colour, which can help if you are having to make large adjustments to colour/contrast.

[newb2pro_1day_or_so]

Thanks for setting that rumor straight. I wasn't sure if that was true. I had heard before that jpegs deteriorate over time, but I was never sure how.

[davidcrebelxt]

I take the raw and process it slightly, convert to jpeg and do most if not all my processing in CS2. I do keep some RAW images if I really like the picture and think it has a high potential.

Also, do AS MUCH as possible in the RAW converter itself before converting to either .tif or .jpg. I personally keep all my RAW images (except the out-of-focus, ground-shots, etc.) that way I can go back and process the RAW differently, or use new tools that were not available at the time, etc.

[RAWuser]

Also, do AS MUCH as possible in the RAW converter itself before converting to either .tif or .jpg. I personally keep all my RAW images (except the out-of-focus, ground-shots, etc.) that way I can go back and process the RAW differently, or use new tools that were not available at the time, etc.

An eat-up-all-harddrive-space-in-a-hurry method for sure but worth every byte for this ability to go back and try editing the picture again without any loss. Before RAW, I used to make a copy of the original jpeg and worked off the copy jpeg instead. I always hated not having access to the originals in those rare occasions where I totally trashed a picture and accidentally saved it. With RAW, I love being able to click on that right-click menu: "Clear Camera Raw Settings" in Adobe Bridge, lol.

[davidcrebelxt]

With RAW, I love being able to click on that right-click menu: "Clear Camera Raw Settings" in Adobe Bridge, lol.

An eat-up-all-harddrive-space-in-a-hurry method for sure but worth every byte

Yeah, that's the best, isn't it? Especially now with those new beta profiles for LR2 and ACR 4.5; I'm going back to alot of my RAW's that I notoriously had trouble with the colors, and am going back to take a look at them.

With LR, its nice because for the most part I rarely actually convert to .jpg. I'll make virtual copies (no disk space.) Or if I do for posting to web or sharing, I can delete those exported photos when finished with them, knowing they're just another export away.

[Bobster]

I had heard before that jpegs deteriorate over time, but I was never sure how. not another one! where do people hear these things from?!

[René Damkot]

An eat-up-all-harddrive-space-in-a-hurry method for sure

Not nearly as much as keeping a layered .psd file for every image ;)

[Zazoh]

JPEGs deteriorate if they are saved multiple times. You can open them as many times as you like and it will have absolutely zero effect on the file.

There are certain programs that allow non-destructive saves of JPGs, DPP is one, and Picasa2 protects the original JPG so that it can be reverted back to.

I've seen tests online where files were saved over 20 times without visible change, but I think it depends on subject matter.

[RAWuser]

Not nearly as much as keeping a layered .psd file for every image ;)

For every image? Lol, that can't be too much fun to sort through.

[newb2pro_1day_or_so]

I realized I usually only save a jpeg once and then I mark it in a set to know it's been edited. Once the whole group is finished I store it on my hard drive and my website. I rarely come back to save a second time or to make any changes because most of my editing can be done in one sitting as I don't do extreme makeovers to my shots.

[tim]

not another one! where do people hear these things from?!

DPreview? ;)

[gcogger]

There are certain programs that allow non-destructive saves of JPGs, DPP is one, and Picasa2 protects the original JPG so that it can be reverted back to.

I've seen tests online where files were saved over 20 times without visible change, but I think it depends on subject matter.

AFAIK the only non-destructive saving that's possible is for images that you rotate by a multiple of 90 degrees. I can't see how it would be possible for other edits to be saved without causing further deterioration of the JPEG?

[tim]

There is no such thing as a non-destructive save of a JPG.

This areas pretty simple, but hard to explain. If you open a RAW file in Photoshop, edit save as jpg (without closing), edit more more, save as jpg, edit some more, save as jpg, you've still only done one save to the file. It's only when you open a file then save and close it you lose quality. Hopefully that makes sense. Think about how things work, with the opening, decoding, manipulation, and encoding again, it's easy to visualise if you're an enginner ;)

[Bobster]

AFAIK the only non-destructive saving that's possible is for images that you rotate by a multiple of 90 degrees. I can't see how it would be possible for other edits to be saved without causing further deterioration of the JPEG?
ok whats your logic behind that one??

[René Damkot]

You can do a (lossless) jpg rotate, but not by opening, rotating and then saving.
If you do that, the jpg gets re-compressed, thus quality is lost.
DPP can do a "lossless" edit to a jpg, as can LR and ACR, but again, the file will need to be saved (thus compressed, thus with IQ loss) for the edits to be visible in other software...

[Bobster]

yeah but doing a rotate of a JPG without opening i wouldn't call an edit..

[gcogger]

yeah but doing a rotate of a JPG without opening i wouldn't call an edit..

The file has changed, and been saved with a new time/date stamp. Personally I'd call that an edit, but you're free to see things differently. I don't see there's much to be gained by arguing over the meaning of the word 'edit' :)

[Bobster]

viewing a JPG in something like Windows Picture Viewer and asking it to rotate an image isn't saving anything..

[gcogger]

viewing a JPG in something like Windows Picture Viewer and asking it to rotate an image isn't saving anything..

I think we're talking about different things here. What I, and some others, are talking about is the ability of some applications to perform a lossless rotation on a JPEG file. I tend to use an old copy of Paint Shop Pro for this. When you do that the file is actually changed and resaved, so that the image has been rotated for any application that opens it. The data in the file has changed, although the image has not been opened for viewing. Due to a special technique, sometimes known as extreme cleverness :), this can be done with the compressed data directly, so that the file does not need to be compressed for a second time when it is saved. If the file is opened and viewed in the application first, then a rotation performed, the change is made on the un-compressed data. In this case it needs to be compressed again on saving and the rotation is therefore not lossless.

[René Damkot]

When you do that the file is actually changed and resaved,

AFAIK (and I might be wrong) all that's changed is the file header.
Same as when you set your camera to rotate the file for instance...

[gcogger]

AFAIK (and I might be wrong) all that's changed is the file header.
Same as when you set your camera to rotate the file for instance...

Hmm... I think this merits further investigation...

OK, I tried using PSP to perform a lossless rotation on a small JPEG. Then I used Windiff (which compares the binary data of 2 files) to compare the original and the rotated version. According to Windiff, the data in the 2 files is completely different, except for a couple of lines at the beginning of the files. That suggests that PSP at least will modify the data in the file rather than just the header. If I again use PSP to rotate the second file back to the original orientation, then Windiff shows it to be virtually identical to the original file (barring one line at the start of the file, and one line at the end).

This suggests that the data itself is actually transformed by a lossless rotation, but I'm willing to be proved wrong if someone knows the answer for certain?

[Zazoh]

AFAIK the only non-destructive saving that's possible is for images that you rotate by a multiple of 90 degrees. I can't see how it would be possible for other edits to be saved without causing further deterioration of the JPEG?

Picasa2 saves the original, untouched. Technically it is not non-destructive, but it doesn't matter because you can always revert to the original.

DPP saves the information in instructions just as it does for RAW. So you can do thousands of saves, of course you can't see in other programs till you output, but who cares, you are only doing that once.

By the way, this isn't theory, it is in the documentation of both the programs.

[davidcrebelxt]

I've noticed that at certain pixel ratios Windows internal picture viewer will pop up a message saying that because of dimensions of the image, the rotate will not be lossless... do you wish to proceed. In many cases this warning does not pop up (implying lossless rotation?)

Couple of resources I found with a quick search on the issue (not sure how up to date they are):
http://graphicssoft.about.com/cs/digitalimaging/f/rotatequality.htm
http://sylvana.net/jpegcrop/losslessapps.html