[quote name='PuxaVida' timestamp='1288088807' post='3785']
Just to avoid misunderstanding: Do you mean that producing a pure raw data requires state of art algorithm for data processing? I'm not a sofware engineer, but developing a data compression algorithm which enables high compression ratio without a loss in IQ sounds more challenging...
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I meant the compression algorithm, not the raw processing. And I did not say challenging. It is certainly not challenging to implement a compression algorithm, but using it needs processing power. If you want to keep a high burst rate, you have to compress the data fast.
[quote name='PuxaVida' timestamp='1288079248' post='3783']
But I doubt that (not that I pixel peeped and saw differences on screen, yet). But on the D700, the uncomressed option produces ~22-24MB files, while the "lossless compressed" produces ~10-12MB.
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So what? There are ways to compress things without loss. Not every compression is lossy. I don't know whether this is the case with Nikon's compression - I'm simply challenging the notion that the fact that compression happens equals loss of information.
[quote name='BG_Home' timestamp='1288131299' post='3807']
So what? There are ways to compress things without loss. Not every compression is lossy. I don't know whether this is the case with Nikon's compression - I'm simply challenging the notion that the fact that compression happens equals loss of information.
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I don't say that the loss in IQ is proportional to compression ratio...It was just a remark... OTOH, I'm not sure that the "lossless compressed" NEF is 100% lossless. Most probably it's hard to see the difference in sRGB gamut even in a decent IPS monitor. But I believe that "uncompressed" is more lossless than the "lossless compressed".
Regards,
Serkan
[quote name='PuxaVida' timestamp='1288163839' post='3809']
I don't say that the loss in IQ is proportional to compression ratio...It was just a remark... OTOH, I'm not sure that the "lossless compressed" NEF is 100% lossless. Most probably it's hard to see the difference in sRGB gamut even in a decent IPS monitor. But I believe that "uncompressed" is more lossless than the "lossless compressed".
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I replied all the time without reading up the specs.
According to the D700 manual (p. 67 in the English version), this camera can write "uncompressed", "compressed", and "lossless compressed". The manual also tells something about the losses in image quality. There would really be no point in allowing for two options if both of them are lossy after all.
Nikon states that the lossless compression yields 20-40% reduction in file size. Try to apply some gzip, zip, 7-zip, or whatever you want to an uncompressed NEF and you will probably find that you can reduce file size by 20-40% or even more. You will agree that gzip or zip is lossless and that Nikon should be able to implement something similar in their cameras.
[quote name='ThomasD' timestamp='1288167853' post='3810']
I replied all the time without reading up the specs.
According to the D700 manual (p. 67 in the English version), this camera can write "uncompressed", "compressed", and "lossless compressed". The manual also tells something about the losses in image quality. There would really be no point in allowing for two options if both of them are lossy after all.
Nikon states that the lossless compression yields 20-40% reduction in file size. Try to apply some gzip, zip, 7-zip, or whatever you want to an uncompressed NEF and you will probably find that you can reduce file size by 20-40% or even more. You will agree that gzip or zip is lossless and that Nikon should be able to implement something similar in their cameras.
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Do the raw converter programms (like ACR) uncompress the "lossless compressed" image data or use the produced NEF file as it is recorded by Nikon's compression algorithm? I ask this because first of all I don't know the answer; and second of all, zipping & unzipping is done by the same application, but here in NEF case the applications on the compression and uncompression side are different.
Kind regards,
Serkan
[quote name='PuxaVida' timestamp='1288169519' post='3811']
Do the raw converter programms (like ACR) uncompress the "lossless compressed" image data or use the produced NEF file as it is recorded by Nikon's compression algorithm? I ask this because first of all I don't know the answer; and second of all, zipping & unzipping is done by the same application, but here in NEF case the applications on the compression and uncompression side are different.
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Of course, any software cannot use the compressed data without uncompressing it (ever tried to read a zipped text file?).
And of course, the raw converter has to know the algorithm that was used to compress. I don't know how this is managed. A NEF is essentially a TIF, so it may be that the standard TIF compression algorithm (LZW) is used, which is known by most applications. Or Nikon releases some information if they use a proprietary algorithm.
To summarize, when using lossless compression, there is no possibility that image quality is lost by using a non-optimal decompression algorithm, because there is nothing like a non-optimal algorithm.
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