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Old Jan 19, 2007, 12:02 PM   #1
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Hi All,

Just bought my first camera… ever and trying to figure this doohickey out.



Here's my question, when in full auto mode, (green square), I have set the image quality to high – fine. I has assumed that the jpeg file size would be the same as the camera's megapixels, at 10. Yet, they vary from 3 to 4 Mb.



1 - Excluding RAW, am I getting the most out of the image quality?



2 – How come the file sizes vary, why are they not all the same if they are shot at the same settings.



Is this due to the camera's compression tool that decides on how to bets keep the image quality yet make the file smaller?



Thanks!
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Old Jan 19, 2007, 12:30 PM   #2
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jpegs are compressed. To get highest quality you have to select RAW but then you need to process those RAW files which adds an extra step.
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Old Jan 19, 2007, 1:06 PM   #3
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Thanks Bobbyz,

I think I understand the compression and jped idea but what throws me is the variable sizes.



Why are the file sizes different?



TIA
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Old Jan 19, 2007, 2:09 PM   #4
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Each pixel in your jpeg image is made up of three color values - one value each for red, green, and blue. It takes one byte to represent each color, so it takes three bytes to represent one pixel. If your camera gives you a 10 megapixel image (i.e. 10,000,000 pixels), then you would need 30,000,000 bytes to save that image in an uncompressed format. In the binary system we go in steps of 1,024 (a convenient binary number) instead of 1,000 so 30,000,000 bytes is equal to 30,000,000/1,024 = 29,297 kilobytes which is equal to 29,297/1,024 = 29 megabytes. So your 10 MP camera will give a 29 MB uncompressed image file. The jpeg compression algorithm looks for areas of similar color and groups them together, thus reducing the file size. A picture with large amounts of similar color, say a picture of a cloudless blue sky, can be compressed much smaller than a picture that contains a lot of fine detail and different colors. So the reason why your jpegs are of different sizes is because it depends on what you took a picture of.
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Old Jan 19, 2007, 3:11 PM   #5
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AH HA!!!



Thanks edwardr!!!
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