topic Does a longer exposure result in a larger file size? in EOS DSLR & Mirrorless Cameras

Does a longer exposure result in a larger file size?

stevet1 — Thu, 29 Feb 2024 22:21:42 GMT

I was just curious.

If I take a 30 second exposure, and an exposure of 1/200th's of a second, is the 30 second exposure a larger file size; i.e. more bytes?

Steve Thomas

Re: Does a longer exposure result in a larger file size?

kvbarkley — Thu, 29 Feb 2024 22:29:22 GMT

For Raw files, no.

For jpegs, the more noise the larger the file. So assuming that the 30 second exposure does not just blow out the whole image leaving it totally white, a longer exposure can result in a larger file.

During an idle moment, I actually looked at the number of files remaining as a function of ISO, and larger ISO's resulted in fewer files.

For my T6S:

I am not sure what card brand has to do with it, though. 8^)

Re: Does a longer exposure result in a larger file size?

kvbarkley — Thu, 29 Feb 2024 22:47:28 GMT

Putting my nerd hat on, it has to do with information theory. Random data is not compressible, so the more noise in the data, it is harder to reduce the file size. In fact, the compressed size may *increase* with very random data.

Text is easy to compress because it is pretty predictable, with lots of redundant info in the coding method.

JPEG (and MP3) work by throwing away information you can't perceive anyway.

In fact, it is not as common as it used to be, but occasionally you hear about people claiming to have invented a miraculous lossless compression method that works on all files, and can be "run on itself" to get even smaller files. This is snake oil.

https://www.computerworld.com/article/2793144/experts-question-compression--breakthrough-.html

http://rationalnumbers.james-kay.com/?p=1656

Re: Does a longer exposure result in a larger file size?

Waddizzle — Fri, 01 Mar 2024 00:55:08 GMT

“ I am not sure what card brand has to do with it, though. 8^) “

It may have more to do with burst rates than files sizes. =8^0

Re: Does a longer exposure result in a larger file size?

Peter — Fri, 01 Mar 2024 05:47:06 GMT

More heat, more noise, larger file size. Easy to try.