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t024484

8 bits versus 16 bits, continuing.

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Hans, I'm afraid I cannot be of service there. I'm not much of a portrait photographer at the best of times, and I have never used the DMR for portraits. I know there are some members doing great studio stuff with the DMR. Maybe one of them can help out?

 

Jaap,

 

No problem, you were already of great help. I have already traced someone who has made great pictures from human faces with a DMR. I hope he will react to my request.

 

Hans

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diogenis--

You're basically right that the firmware writes out the values for each image, but as I understand, it's the rules for building the LUT which are stored in firmware, and not the LUT per se. The rule for that computation is what t0 has quoted in the paragraph you cite. That's why the algorithm could be replaced relatively easily.

 

For more information on the M8's compression algorithm, with its advantages and disadvantages, see Michael Hußmann's article on the topic in LFI from about the time the question of 8 vs 16 bits first became popular, a few months after the M8 came out.

 

Hans is certainly subjecting the matter to some good, enthusiastic investigation.

 

Howard,

 

I did not find the rules in the firmware, what I showed are the addresses from/to in hex where the real LUT's are stored.

The rules for building the LUT's that I showed, is what I extracted from these LUT's.

 

Hans

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In any case, Im sure big brother is watching and after dust has settled (photokina) we can hope for some firmware upgrade

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I you want to give it a try, I will make a software release with Log compression.

And no, compression cannot be taken away.

Yes, I would like to give it a try just to see what it looks like.

Can you describe the reason why compression cannot be removed?

 

Regards

Henrik

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Yes, I would like to give it a try just to see what it looks like.

Can you describe the reason why compression cannot be removed?

There might be nothing precluding a modification of the firmware so the camera would write uncompressed data, only rewriting the firmware isn’t that easy. But for changing the compression method, all that has to replaced is data, specifically the entries in the two look-up tables, with (probably) only the checksum issue to be resolved.

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I did not find the rules in the firmware, what I showed are the addresses from/to in hex where the real LUT's are stored.

The rules for building the LUT's that I showed, is what I extracted from these LUT's.

Hans, thanks for the correction.

 

Then if I understand, the firmware contains 256 discrete values which it copies into each DNG?

 

So the two lookup tables you and Michael are speaking of are:

1) the LUT which the firmware uses to compress the image; and

2) a second LUT which is copied into the DNG for decompression by external software?

 

Thanks.

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