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09/22/2005 10:33:10 PM · #1 |
Just wondering if anyone can bust this myth
The more that you open a jpeg file the more the quality will deplete.
I have heard this from my instructor at school but it is kind of hard to believe. |
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09/22/2005 10:34:58 PM · #2 |
no way, opening a jpeg should not be altering any data at all
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09/22/2005 10:35:48 PM · #3 |
Originally posted by gclark:
Just wondering if anyone can bust this myth
The more that you open a jpeg file the more the quality will deplete.
I have heard this from my instructor at school but it is kind of hard to believe. |
Opening, no. Processing and saving again and again, yes. |
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09/22/2005 10:38:33 PM · #4 |
In fact it's very true.
You save a file as JPEG it's compressed and loses some quality, but saves disk space. Let's say you open it in Photoshop the JPEG file is converted to some format PS understands and then you compress the earlier compressed data again.
Just try it, you don't have to do it many times to notice.
I always use TIFF with zip compression instead. Though the files are a lot bigger it's lossless, which JPEG surely isn't.
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09/22/2005 10:40:41 PM · #5 |
But if you open the jpeg, save a version, and then open the original again and do a different edit process, you lose nothing but in the saves. However, if you open a jpeg, save in .psd or .tiff, you lose almost nothing through the edits with multiple saves until you save as a .jpg again.
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09/22/2005 10:46:46 PM · #6 |
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09/22/2005 11:04:55 PM · #7 |
Thank you
That is what i thought so as long as you never save the jpeg again you will lose no quality |
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05/28/2006 04:29:58 PM · #8 |
| Don't keep resaving JPEGs, the compression algorithm discards data when saving and interpolates when opening again. Keep everything in a lossless form (TIFF or PSD), and only save as a JPEG when you need it for web or something. |
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05/28/2006 04:45:06 PM · #9 |
I've personally saved over something in JPG like 10 + times, and never noticed a reduction in quality...and I have 4x6's, 8x12's, and so on to prove it. Of course that's saving at like 100 or 12, which is the maximum. Obviously if you're saving at 80 or 9 or whatever, there's going to be a quick drop in quality.
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05/28/2006 04:48:06 PM · #10 |
| I save all mine as Tiff files no compression |
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05/28/2006 04:53:52 PM · #11 |
| Saving over a JPEG at maximum quality once or twice will most likely be unnoticeable, but you are still causing a generational information loss. Do it enough times and you will notice it. I myself prefer to keep information loss to a bare minimum. |
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08/20/2006 05:29:02 PM · #12 |
Originally posted by Kronus:
I save all mine as Tiff files no compression |
You can compress TIFF's losslessly, that way you save a bit on space. Takes longer to open and save them though. |
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08/20/2006 05:40:25 PM · #13 |
Originally posted by gclark:
Thank you
That is what i thought so as long as you never save the jpeg again you will lose no quality |
That is correct.
If just opening the file were the case, you'd lose quality each time Windows (Mac OS, whatever) generated a thumb for you to view.
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08/20/2006 05:42:36 PM · #14 |
| Many of the BIG stock photo companies are now asking for submissions in JPG only. In fact they even say it's ok to shoot the pic in JPG. They only require the same quality and that the pics uncomressed are at least a certain size. With the newer programs and the JPG compression the loss is minimal especially if saved at level 12 highest quality. If ya re-save even the level 12 a LOT of times it may show some artifacts. If you plan on changing the photo save it as a TIFF and change it just to be safe. |
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08/20/2006 05:59:37 PM · #15 |
I just leave the files as they came from the camera - jpeg or raw - and any edits are done to a copy. i have tons of original photos, as a result, that i never have time to go through. BUT, i don't even have to worry about compression issues, etc. if i have an ongoing project in photoshop, i save it as psd, or tiff, and make jpeg copies with the same name at different stages for organizing puposes.
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