TeamSpeed wrote in post #9566772
I don't think raw matters too much on the ISO setting, since it is the raw uncompressed data. For JPGs though, this is true because with higher noise levels, there are fewer consecutive pixels with the same values that could be compressed together. If I am wrong, it won't be long before I am corrected!
There is lossless compression in RAW files, unlike the lossy compression in JPEG files. Otherwise the file size would be about 1.75 bytes per pixel (14 bit RAW); a 7D with 18 MP would have RAW files of about 31-32 MB.
HankScorpio wrote in post #9567035
No it doesn't. ISO has no effect on file size. Image content does though.
ISO does affect file size in that higher ISO settings give you noisier images, so the files are less compressible.
HankScorpio wrote in post #9567287
No it won't unless by changing the ISO you also change the exposure and therefore the content of the image. The tendancy of a high ISO to expose the shadows slightly to the right and therefore increasing the recorded detail does not equate to high ISO creating larger files.
By your reasoning, it's not high ISO settings but exposing to the right (which most of us habitually do) that adds file size. Using the same exposure settings for the same scene at different ISO values will lead to one horribly underexposed shot or one horribly overexposed shot, so from that standpoint I suppose you could conclude that more detail is being captured by a high ISO shot at the same exposure setting, but that's a nonsensical comparison. The only meaningful size comparison of two photos of the same scene is of two properly-exposed photos of the same scene. And in that case, sensor (high ISO and/or long exposure) noise will play a noticeable role in file size.