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12-25-2007, 08:09 AM   #1
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Little confused,need help please!

Converting from Pentax PEF(RAW) to JPG you loose mega bites, why? Does it mean you loose quality for printing? I've done a test, when you convert one PEF at a time rather than select a lot of PEF's and convert to JPG, the file size is bigger when doing one-one? The dimensions of the photo, is that where the quality lies for BIG printing. Sorry guys, bit confused here, help please.. Thanks. Gerrie

12-25-2007, 10:13 AM   #2
Ole
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JPG is a compressed file format. During compression of the image file some data are lost and this reduces the image quality.

The degree of compression can be adjusted in most converters. A low degree of compression results in only little infiormation lost, and you may not notice any image degredation at all when printing.
12-25-2007, 10:48 AM   #3
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I convert PEF to JPEG at it's highest quality setting. I converted a photo to JPEG and also to TIFF, which gives a larger file than the PEF, and had them both printed. I could find no difference in the quality of the prints.
12-25-2007, 11:12 AM   #4
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Thanks

Thanks guys. Yes, it's more a lack of knowledge on my side than confusion. Will have to do a bit more reading on this.

12-25-2007, 12:35 PM   #5
PDL
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For a good discussion about RAW - JPEG ---- read ---- this:
Understanding RAW Files Explained

As for why to shoot RAW in the first place ---- read ---- this:
White Balance Follies

The conversion of RAW to JPEG - loses data (and data is what digital imaging is all about), that is the nature of JPEG. While JPEG images can, and do, make wonderful images - additional editing of JPEG's by their nature will cause the long term degridation of the image. Each RAW converter - ACR, SillyPIX, Bibble etc. - will "interpret" the information in the RAW file with slight variations. Once you develop a workflow you will be able to provide predictable results.

As mentioned in the Understanding RAW Files article - RAW is closest thing to a latent image that you can get in digital. The JPEG format does compress the image data - and although it is efficient at compressing - the fact of compression means that data are lost given the algorithms used. There have been attempts to update the JPEG standard (remember JPEG 2000?), but they have not caught on. So, we are stuck with a "standard" that is decades old and one that will be around for some time, given the stoggieness of the stanadards organizations plus the imaging world.

The Elitist - Formerly known as PDL

Last edited by PDL; 12-25-2007 at 12:36 PM. Reason: cleared up some language
12-25-2007, 12:49 PM   #6
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QuoteOriginally posted by Ole Quote
JPG is a compressed file format. During compression of the image file some data are lost and this reduces the image quality.

The degree of compression can be adjusted in most converters. A low degree of compression results in only little infiormation lost, and you may not notice any image degredation at all when printing.
If you say a low degree of compression-is this the same as "high" quality conversion? The higher you adjust the quality the less information is lost? With Pentax Photo Browser i've done the conversion from PEF to JPG. The PEF is 16.1MB, converted to JPG=11.2MB. Doing the same using the software FastStone as the converter, i only get 5.21MB. Will this make a huge difference in printing?
Secondly, i've done the trial with one single photo as described above. Then in Pentax Photo Browser i did a batch "JPG extraction" which resulted in the same photo down to 1.42MB (single was 11.2MB). You can't select degree of compression or quality in both actions. Will the 11.2MB JPG be better in quality than the 1.42MB?

Which converter is easy to use (PPBrowser is very slow) and will give good quality conversions? Sorry for throwing so many questions... Thanks. Gerrie
12-25-2007, 12:59 PM   #7
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QuoteOriginally posted by PDL Quote
For a good discussion about RAW - JPEG ---- read ---- this:
Understanding RAW Files Explained

As for why to shoot RAW in the first place ---- read ---- this:
White Balance Follies

The conversion of RAW to JPEG - loses data (and data is what digital imaging is all about), that is the nature of JPEG. While JPEG images can, and do, make wonderful images - additional editing of JPEG's by their nature will cause the long term degridation of the image. Each RAW converter - ACR, SillyPIX, Bibble etc. - will "interpret" the information in the RAW file with slight variations. Once you develop a workflow you will be able to provide predictable results.

As mentioned in the Understanding RAW Files article - RAW is closest thing to a latent image that you can get in digital. The JPEG format does compress the image data - and although it is efficient at compressing - the fact of compression means that data are lost given the algorithms used. There have been attempts to update the JPEG standard (remember JPEG 2000?), but they have not caught on. So, we are stuck with a "standard" that is decades old and one that will be around for some time, given the stoggieness of the stanadards organizations plus the imaging world.

The Elitist - Formerly known as PDL
Great reading, thanks PDL.
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