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Old Aug 23, 2004, 4:41 AM   #1
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Having taken one or two less than perfect pictures i needed to adjust the images via software. The images are taken on a 4mp Canon A80 at max res and fine compression and when downloaded to my PC are shown as approx 1MB per image.
Once i have adjusted the images in DCE Enhance ( added a UV filter, sharpen etc ) and saved the resulting image with min compression it comes out at almost 4MB.
How come it gets bigger? Am i missing something obvious. When i have stitched 4 images together it comes out at a little under 4 MB which i can understand ( 4 x 1MB ) but how can DCE enlarge the file by such a degree.
Any help or pointers would be appreciated.
Many thanks
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Old Aug 23, 2004, 1:34 PM   #2
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A 4MP camera will produce a 12 Meg file (R + G + B. The compression in your camera uses a different algorhytm then your software, thus the difference...

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Old Aug 24, 2004, 2:44 AM   #3
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Thanks Dave for taking the time to answer. I am very grateful.
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Old Aug 31, 2004, 1:01 AM   #4
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Actually the algorithm is the same, its the compression setting.

The image is decompressed, modified and then compressed. If the quality level (the compression setting) is set to very high, the file size is larger even there is no more information in the picture.

To get to the right compression level is somewhat difficult since its not stored along with the file. You need to try but the resulting 4MB is by far too large. Try a lower setting, you won't loose information.
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Old Aug 31, 2004, 8:43 AM   #5
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Not so! You will lose information. Everytime you save a JPEG file it does the same compression routine, but uses it on the EXISTING information.

You can prove this to yourself. Load a JPEG and save it at level 6 in photoshop, load it again and save it. Do this twenty times and you wioll be surprised at how bad the resulting picture.

With Photoshop 7, Adobe intorduced a VERY fine level of JPEG, which is level 12. At this level its very hard to see any degradation in the image no matter how often you wrok with it. However, anything less will result in BAD images is you load and save, load and save.

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Old Aug 31, 2004, 2:05 PM   #6
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The level 12 uses the max valueof 100 of the JPEG lib which tells the lib not to scale down the quantized values. This results in a rather large file.
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