Why are our raw files so big?

From RAW conversion to image editing and printing
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bfitzgerald
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Why are our raw files so big?

Unread postby bfitzgerald » Mon Nov 05, 2012 10:48 am

Well I played around with the Adobe DNG software and the lossy compression I took a higher ISO NEF raw file and used lossy compression keeping the same resolution (the new software lets you limit the resolution say 15/10mp and other options)
File size went from around 14.5Mb down to 7.5Mb! Almost half..

I then played around pulling the image apart with big changes to exposure and other areas..and did not see any obvious differences in the image.
I'll have to see what it does to the other raw files I have, but I'm starting to think I could save quite a lot of space converting raw to DNG. Even not using the lossy compression it took the 14.5mb file to 12.4mb. (12 bit raw)

I won't do anything yet but I'm thinking that this might be the way to go with raw files from now on.
Not that I would downsize the 16mp Raw files..but if you halve the space taken up that's quite significant IMO

I'm not a natural DNG fan by the way but it struck me how inefficient the raw files from cameras are
Thoughts?

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Dusty
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Re: Why are our raw files so big?

Unread postby Dusty » Mon Nov 05, 2012 11:30 pm

Lossy compression will always bite you in the end. You lose actual data, and can never get back to the exact original.

Lossless compression gets you just a little savings - about 1 meg each on my a350 RAWs, not enough to be worth it unless I'm trying to fit them on an undersized memory stick.

The files are so big because they contain so much data.

Dusty
An a700 and couple of a580s, plus even more lenses.

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bfitzgerald
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Re: Why are our raw files so big?

Unread postby bfitzgerald » Mon Nov 05, 2012 11:58 pm

I found this article
http://www.pointsinfocus.com/learning/d ... lossy-dng/
You can either use the latest version of LR or the Adobe DNG software to convert both seem to be the same thing.
The file size reduction is in some cases pretty huge with lossy, even just straight conversions to DNG seem to offer a decent reduction in size with no penalty.
I'm of the view that it could be useful..and that in some cases you have data that is empty or wasted or not being effectively compressed.

Bit like me making a 50mp ISO 400 neg film scan..sounds great but really I might have 10mp of data.


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