NX300 Official - See the News!

Started Jan 3, 2013 | Discussions thread
viking79
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Re: NX300 Official - See the News! - what size files ?
In reply to jgardia, Jan 4, 2013

jgardia wrote:

Unless you want lossy compression you aren't going to do much better than that. A RAW file is 12 bits and has an embedded JPEG. With no compression on your NX10 that is 14.6 MP * 12 bits = about 21 Megabytes plus maybe 1 or 2 MB for embedded JPEG. Say 2:3 lossless compression ratio puts it down around 14 MB, plus a low quality JPEG for review and you are up at probably 15 MB.

The 20 MP sensor is going to be 28 MB uncompressed before you had in the preview JPEG. This is not small, and not something you are going to be able to reduce much below 20 MB without lossy compression.

Hi Eric,

I have to politely disagree with you. I made some tests (with my NX10's raw files), and the Samsung raw files are embedding a full jpeg (3.5 to 6mb). The rest (about 22MB) is the 14.7mpix at 12 bits per pixel.

Thanks, I didn't realize the embedded JPEGs were so large, I think in the 20 MP cameras they use a reduced sized JPEG though (i.e. it isn't 20 MP).  I haven't actually measured how large the JPEG is.

You can do differential encoding (I tried it), and you can go to 15MB without any loss. Basically you save the difference between the pixels, instead of saving the absolute value. You can encode the difference in 1 byte per pixel if it fits, and when it doesn't you need 3 pixels. In my tests, you can fit the difference in 1 byte for over 99% of the pixels. The algorithm is super easy, and the concept is super old (I think from the 70s).

I was just saying lossless compressions for images are usually limited to saving around 33% (very rough, and depends on what you are shooting). Like in your example you are going from about 22 MB down to 15 MB (about 33% smaller). If you want to save more space than that, you usually have to go to a lossy compression and I think most like Nikon minimally clip some of the highlight data since it isn't as noticeable.  So I think we agree here.

Thanks,

Eric

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