Nikon lied about lossless NEF compression :(

Started May 16, 2004 | Discussions thread
audioNeil
New MemberPosts: 18
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Re: Nikon lied about lossless NEF compression :(
In reply to quickclick, May 19, 2004

I work on medical image processing. We deal with 12-bit data, and various curves to manipulate it all the time.

Here is the practical results of Nikon companding the data into a 9.4 bit gamma-corrected colorspace:

Pros:
1) Slightly higher compression

2) Faster compression, as Huffman tables are smaller and easier to generate, as well as their being less data to store to the card.

Cons:

1) If exposure compensation needs to be done to reduce the brightness of highlights, there is less data available. Theoretically this can cause contouring of smooth areas of colour.

2) Someone who needs to process an image highly for some reason other than normal photography has slightly less smooth data to work with.

NOTE: The data is still 12-bit dynamic range, and should (though I don't own the programs so I can't verify) be processed as linear 12-bit within the Nikon Capture program. So, the gamma correct should be un-done, and processing will work on the full data range. This means that the "quantization" introduced by the gamma curve will partially get undone by denoising and smoothing algorithms (though will slightly hinder sharpening algorithms).

When the image is JPEG'd or sent for printing, it must be in 8-bit gamma-corrected form anyway. So, the 9.4-bit gamma corrected form is actually a good choice which will not affect the average print.

I would prefer the unmodified 12-bit linear data. But, is when you are talking about quantization inaccuracies that are on the order of the noise, there isn't much to worry about.

Nikon should make this clear in their literature. Yes, their marketing people have glossed over it. However, NEF is lossless, and it provides 12-bits of linear dynamic range (compressed into 9.4 bits of gamma-corrected data). Realistically, even if your final print, owing to quantization, had only 7-bits per plane, you probably wouldn't notice, except on black-and-white on smooth objects (or monochrome objects).

This isn't going to be an issue for 98% of D70 users.

However for the other 2%, it should be documented!

As for "smoothing" at high exposure times -- I would have liked that to be user-configurable! I agree that it isn't good for astrophography for instance. I know the Canon DRebel is widely used for astro work -- and perhaps this is one more reason why it will continue to be the best (long exposures are the norm there). For the rest of us -- how often will we be doing exposures over a second?

I am still leaning towards getting this camera -- especially since I may be able to convert my manual lenses to work with matrix metering (like my beloved 105 f/1.8). If I were asked, as an imaging programmer, to improve compression with acceptable loss, I might have chosen the exact same solution as Nikon.

Neil

quickclick wrote:

Rant on!

I feel cheated. Nikon is companding the raw data down to 9 bits.
I want all 12-bits in my NEF files. I can take having to send the
D70 off for a month to get the focus fixed. I can even take the
back of the camera rattling after the service procedure.

But, I will not accept NIKON crippling what would otherwise be a
perfectly good camera. If NIKON does not release a firmware patch
to provide lossless NEF before Canon releases its 10D replacement;
I will loose some cash switching. Grrrr

I first heard about this in this thread:

http://forums.dpreview.com/forums/read.asp?forum=1034&message=8801945

Here is a detailed exlanation:

http://www.majid.info/mylos/weblog/2004/05/02-1.html

I am even more angry; because I just wasted more money buying a
70-200VR.

Not happy...
--
Visionary Imagery, inc

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