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05/25/2007 09:34:38 AM · #1 |
we where talking in college today about file formats, i always knew that u lost image quailty each time you changed or resaved a JPEG but today i got told that its when you open it aswell =O haha
so ive just saved some of my best pictures a .tiff and disadvantages to .tiff apart from the HUGHH file size (one is 111mb O_O haha)
ta =DDDD |
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05/25/2007 09:38:43 AM · #2 |
| If you save the TIFF file with the LZW compression option, the file size on disk will be smaller, though you will suffer some delay in opening it as it decompresses, and not all programs will allow placement and printing of a compressed TIFF. LZW is lossless compression, essentially the same as ZIPping a file. |
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05/25/2007 09:41:22 AM · #3 |
| woo thanks good to know (Y) |
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05/25/2007 09:45:45 AM · #4 |
Don't believe everything you here in college. You DO NOT lose quality just by opening a JPEG image. If that were indeed the case, all the nudes on this site would be unrecognizable in about 2 days.
Your instructor is misinformed at best.
Message edited by author 2007-05-25 09:46:50.
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05/25/2007 09:45:57 AM · #5 |
PNG is also good but photoshop is a bit slow at saving huge files (like large scans).
It supports 16 bit and compress photos around 2:1 probly 3:1 at best. PNG is great for screen shots it saves most screen shots (that dont include photos in the screen shot) about 40% smaller then the equivalent jpeg, because most program screen shots dont have that many colors. |
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05/25/2007 09:46:58 AM · #6 |
haha i suppose, his word where "everytime the JPEGS state is changed, it looses quality"
=D |
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05/25/2007 09:51:54 AM · #7 |
Originally posted by exclamationjay:
haha i suppose, his word where "everytime the JPEGS state is changed, it looses quality"
=D |
Anytime you open and then resave it, yes, it will lose quality through lossy compression. True and quite logical.
The simple fact of opening the file is not going to change any data in the file (other than some metadata with a last accessed tag). You'll only lose quality at Save.
As long as you never overwrite your original file, the loss is minimal.
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05/25/2007 09:51:59 AM · #8 |
Originally posted by exclamationjay:
haha i suppose, his word where "everytime the JPEGS state is changed, it looses quality"
=D |
JPEG compression throws out high frequency components and reconstructs them when you open the file. Every time you resave a JPEG you lose more and more information, generational data loss. |
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05/25/2007 09:53:05 AM · #9 |
Originally posted by exclamationjay:
haha i suppose, his word where "everytime the JPEGS state is changed, it looses quality"
=D |
Which translates to "every time the file is re-written" in other words, upon saving. Opening a file can't change the file on disk, therefore there can be no degradation. |
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05/25/2007 09:54:02 AM · #10 |
| I believe that starting in Photoshop CS, the highest-quality JPEG setting is lossless compression. |
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05/25/2007 09:58:35 AM · #11 |
Originally posted by GeneralE:
I believe that starting in Photoshop CS, the highest-quality JPEG setting is lossless compression. |
Now id love to be wrong, i had been searching for JPEG-LS support in photoshop. But from what ive read its not in CS or CS2 by default. I saw a plugin for it somewhere.
Dunno if anyone has more info id like to hear it. |
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05/25/2007 10:24:59 AM · #12 |
FWIW, I only archive RAW files and some of the finished JPEGs files (usually unsharpened). I rarely keep intermediate PSD files.
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05/25/2007 10:34:59 AM · #13 |
Is DNG ever going to catch on?
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05/25/2007 10:48:32 AM · #14 |
Originally posted by GeneralE:
I believe that starting in Photoshop CS, the highest-quality JPEG setting is lossless compression. |
Even the highest quality jpeg has some compression. It will just take longer to turn it to mush by opening and resaving.
Message edited by author 2007-05-25 10:48:46. |
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05/25/2007 10:54:19 AM · #15 |
Originally posted by Man_Called_Horse:
Is DNG ever going to catch on? |
DNG is a container format for raw data. WHile its great and all unless you demosaicisze (spelled that wrong). It might be uncompatible in some readers. You have the option todo that in the converter but it does warn about it affecting the data some.
I like the concept though.
Message edited by author 2007-05-25 10:54:47. |
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05/25/2007 11:02:40 AM · #16 |
Originally posted by Man_Called_Horse:
Is DNG ever going to catch on? |
In theory, DNG solves the issue of always having to upgrade your RAW converter for every new camera body for which you want to read RAW files. In practice, it's only truly useful if camera manufacturers adopt it. The realities of the marketplace are such that the manufacturers are reluctant, believing that folks should be using *their* software for conversion. Nikon in particular has an investment, since they sell their full-featured converter.
I don't think that the current scenario can persist for too long. We simply can't continue to write specific conversion algorithms for every single camera, especially when the camera manufacturers are not forthcoming about the specifics of the formats. |
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