Compressed RAW? (I know it's been discussed before)

zirtico · Oct 23, 2009

On the D5000, I just can't help but think it's a lossless compression. According to dpreview, the sizes on the 12 MP models (D300, D300s, D3) a 12-bit lossless compressed RAW file is about 11.5 MB. On my D5000, I'm hitting nearly that figure all the time. I've gotten up to 12.6 MB and down to 10 MB. I think it could well be a lossless compression in this camera, even if Nikon didn't spread the word on it. What say you?

WineO · Oct 23, 2009

Lossless Compression is a bit of a misnomer but Raw is a 'lossless' format. As I understand it you won't notice any loss but mathamaticaly their might be some.

The size of the Raw file depends on the amount of information contained in the image you recorded. Loss will only occur when you save to Jpeg and will continue to do so every time you resave. Many people save to either Tiff, Dng or Psd untill they need to output the image and thereby avoid lossey formats.
Claude

zirtico · Oct 23, 2009

You're right. I know that there's a bunch of values skipped in the compressed RAWs, but I was just wondering since the file sizes of lossless compressed 12-bit is exactly the same as the ones for D700, D300, D300s and D3. And it is actually quite important to me as I do do a fair bit of processing to recover as much detail as possible. I'm borrowing a D5000 because of money constraints at this point. So I was just wondering about that stuff if anybody else had noticed it.

davidried · Oct 24, 2009

The D5K uses a lossy compression. Whether or not you can notice the differences is up to debate.

lemon_juice · Oct 24, 2009

zirtico said:
On the D5000, I just can't help but think it's a lossless compression. According to dpreview, the sizes on the 12 MP models (D300, D300s, D3) a 12-bit lossless compressed RAW file is about 11.5 MB.

No, it is lossy compression. It would be impossible with current lossless compression algorithms to get anywhere near the size of 11.5MB per image - the sizes would be at least 2 or 3 times larger at that resolution.

zirtico said:
On my D5000, I'm hitting nearly that figure all the time. I've gotten up to 12.6 MB and down to 10 MB. I think it could well be a lossless compression in this camera, even if Nikon didn't spread the word on it. What say you?

Only higher-end Nikons have lossless RAW option - d300 and above. But in practice RAW can be treated as lossless because the compression is so efficient that it makes no difference unless you take extreme measures to look for the difference, it's way better than the best possible JPEG.

--
Michal.

zirtico · Oct 24, 2009

Regarding 2 to 3 times the file size for a losslessly compressed 12-bit RAW, take a look at this: http://www.dpreview.com/reviews/nikond700/page13.asp . Scroll down to see 11.5 MB being the average size for a 12 MP 12-bit lossless compressed RAW. If you look in the "Timings & Sizes" and "Performance" sections of the reviews of D300, D700 and D3, you'll see that they're all the same size for that resolution.

Patco · Oct 24, 2009

lemon_juice said:
Only higher-end Nikons have lossless RAW option - d300 and above.

The NRW files from my P6000 are nearly 22MB.

I haven't really looked into it, but I would have to think they are 12 bit uncompressed lossless raw files, as well.

--
Patco
A photograph is more than a bunch of pixels

Forwardfold · Oct 24, 2009

Nikon compresses raw data in a lossy fashion by taking advantage of fine gradations of levels in highlights that are (arguably) imperceptible to the human eye. Humans are creatures that notice subtle changes in shadows, not highlights. We may have evolved this way to react to danger lurking in the shadows. My educated guess is that the compression is indeed imperceptible. Cheers, Peter

Forwardfold · Oct 24, 2009

Just want to add a reference for my previous statements:

http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html

Scroll down to:

An aside on "lossy" NEF compression

What is written seems very credible.

Cheers,
Peter

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Compressed RAW? (I know it's been discussed before)

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