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Editing JPEG's
We are all told from day one that, when editing JPEG's, quality is lost when re-saving the image. I assume this is true because I have seen that the image size is much smaller after the edit and re-save. So, what is the answer? Do you save the file as a TIFF, BMP, etc.; then edit and save, then re-save as a JPEG to save space on the disk or CD? Do you lose quality during the final re-save to JPEG. As a further nit-picking question:..

Comments (12)

Dave, I happen to think this is one of the most legitimate questions. First, when you say that the "image size is much smaller", you must mean "the file size is much smaller." This is because the default quality/compression mode of your editing software is lower than that of the camera. My camera saves with a compression ratio of 10:1. That's a fairly good JPEG quality. When I save, ONCE, after editing on my computer, I also get a further reduction in file size with not much further loss of quality. For the important work, where I know I may want to edit now and maybe again later, I absolutely want to save in a lossless format.

If you continue to save in JPEG, it really gets ugly really quick. Not only that, but you've destroyed the original and can't bring it back. So for important work, I recommend saving a backup copy of all the original images, in JPEG. That does not take that much place. If I want to edit an image, I first save it in bitmap, unless I am totally done with it, in which case I normally save in JPEG.

And when you do this, you will lose only "a little bit of quality". The amount of artifacts introduced in the picture is also dependant on the scene. Mike..

Comment #1

Yes, Mike, I did mean file size rather than image size.

Thank you for your input.

If I understand correctly, you use the BMP format for editing simply because that is what your software insist on. I've noticed that my software warns me, when saving to TIFF, that I will lose EXIF information.

Is this also the case with BMP? Thanks again,.

Dave.

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Comment #2

You're welcome, Dave. My programming language readily accepts bitmaps and JPEGs. I would otherwise have to decode the file myself. Instead, when I need to, I use another program to convert TIFF files to bitmap images, without loss of quality, which I then load into my software. I can decode an uncompressed TIFF with relative ease, but would be struggling trying to decode a compressed TIFF file. TIFFs and JPEGs allow for saving Exif data.

So it doesn't even tell me about losing the Exif data. Note that my software calls PaintBrush to do the actual editing. In the (near) future, I will modify my software to retain the Exif data and put it back after editing. It's kind of nice to not only have the shooting details, but to keep in the file a short description of the image. Mike..

Comment #3

Hi,.

I was wondering if I shoot in jpeg does it make a difference if I edit it as a jpeg and then save as a tiff or if I save as a tiff and then edit and then save still as a tiff? Dave D..

Comment #4

Dave, The very best results will be accomplished by using TIFF throughout, as you described. But this is at cost of speed (time between shots affected by time to save the larger file) and memory. When the camera saves to JPEG, it is already doing some damage by rounding off color values. The degree of this damage is dependant on the compression ratio and, somewhat, on the scene. The extent of the damage ends there if you then save only to TIFF afterwards. Once you save to JPEG again after editing the image, point values are changed and surrounding pixels take on new (average) values, known as artifacts.

I'm not crazy about that. Besides, for the moment, the work I do does not require this much attention. So I use the fine mode, saving to JPEGs. As I've said, when you're careful to save just ONCE to JPEG, after editing, the artifacts are hard to see. Cheers, Mike..

Comment #5

Hi Mike,.

I don't know if you were aware that you have been answering questions from two Daves. I was the one who posed the original question in this thread.

Thank you again for your expertise.

I assume from your most recent answer that, since my camera offers no option for saving images other than JPEG, my best option is to convert those files I wish to edit to TIFF and never change back again to JPEG.

If that's the best way to preserve quality I will do it though it means getting fewer files per CD when backing up files. Thanks again,.

Dave R..

Comment #6

Dave R, (no, I was not aware!) If you're going to go with TIFF, then it might be worth looking for a file converter that will convert to compressed TIFF. Those files are compressed much like zip files. This is a lossless compression, so you don't have to worry about preserving the quality. I would be tempted to get something that would let me re-construct the EXIF data present in the JPEG. The TIFF format also allows for EXIF data in it's header. I think it's kind of nice to be able to go back and get some of the exposure details some time later.

I would also make sure that whatever software I use for post-processing is capable of reading those compressed TIFF files. You don't really want to have to convert back and forth all the time. But I suspect most photo editors nowadays are capable of reading the files. Though most, as far as I know, will not preserve EXIF data. Cheers, Mike..

Comment #7

Dave R: Just passing through and got to read yout post. If you want to have the highest image quality possible, shoot at RAW > export to a 16-bit .tiff file (this will act as your working file, you can also work with 8-bit files and should fit most of your photographic/graphic purposes) > then export to jpeg or any other desired format. Keep or burn the RAW files they will act as your digital negs. The jpeg file outputted from the 8/16-bit tiff file should have the same quality as the tiff file as long as it was saved with the lowest compression (highest quality) If you want to edit the jpeg, try working with the original tiff file then just output again to jpeg for quality results. Hth, Mike M...

Comment #8

Dave R,.

Most editing software will drop your EXIF info. However, Photoshop CS will retain that even after conversion to TIFF. The much cheaper Jasc Paint Shop Pro 8 will also retain your EXIF info provided you save as Uncompressed TIFF.

Uncompressed files can be zipped later whereas compress TIFFs and Jpegs will not compress any further. Lawrence..

Comment #9

Thanks to each of you for the flurry of suggestions over the weekend.

I wish I had the option of choosing which format I shoot with. Artistic aspirations; pauper's budget (I'm using Minolta's Z1). Which conversion and compression software are you suggesting? Interestingly it is JASC's PSP8 that I am using that is refusing to preserve the EXIF data when I convert to TIFF. Thanks again,.

Dave..

Comment #10

Jasc PSP8 will save as Tiff with the options you last used. To save EXIF, Save As Tiff and then click on Options and then select Uncompressed. The options menu is format sensitive, that is, it will presnet options relevant only to the format you have chosen to save in. So you will have to first select the format and then only selct options. The other Tiff options will drop the EXIF data. I notice that PhotoShop CS and Elements are the same.

Lawrence..

Comment #11

Lawrence,.

It works like a charm. Retained all the EXIF data.

But that is one huge file. I guess I'll just have to decide when it's worth the the extra megs to have a "perfect" picture. Thanks again,.

Dave.

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Comment #12

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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