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Old Nov 26, 2006, 1:00 PM   #1
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Can someone please explain to me how file size is determined, as opposed to image size. For example, I shot a batch of digital photos with a Canon S3iS at High res. All of the images are 2816 x 2112 Image Size, but the file size varies anywhere from 2.8MB to 4.2MB. Can you explain to me what makes one image a larger file size than another? Does it have to do with the ISO settings? or the amount of color in the photo? Appreciate your input.

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Old Nov 26, 2006, 1:17 PM   #2
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dhbref wrote:
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Can someone please explain to me how file size is determined, as opposed to image size. For example, I shot a batch of digital photos with a Canon S3iS at High res. All of the images are 2816 x 2112 Image Size, but the file size varies anywhere from 2.8MB to 4.2MB. Can you explain to me what makes one image a larger file size than another? Does it have to do with the ISO settings? or the amount of color in the photo? Appreciate your input.

dhbref

I have always wondered about this. I believe that the file size is determined by the number of colours,details, shading and compression values. (But I'm willing to be corrected in this thread ..... :roll

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Old Nov 26, 2006, 1:54 PM   #3
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JockScott has pretty much guessed it. The images are compressed as JPGs which work by trying to save only the most necessary data, and using less bits in areas where detail is minimal. So, if you take a picture of a bowling ball against a blurry background, you're going to get a very small file because there's no real fine detail. If you take a picture of some crowded bleachers at a football game, you're going to get a pretty large file.

JPG also uses less bits in areas that are darker as the details aren't as easy to make out. This means that underexposed images will tend to be smaller, but that's kind of a bad thing because it means they won't clean up very easily if you try to fix it on the computer. That's where shooting RAW or TIF files comes in handy.
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Old Nov 26, 2006, 7:52 PM   #4
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Thanks for the reply,

I thought it had something to do with this, but had no clue as to what made the difference.



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