DNG: Sony RX100 files grown 25%

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  • Updated 6 years ago
I managed to convert a small bunch of Raw files from native .ARW to dng.

Here are the settings I used:


I then compressed both the ARW and the dng files.
I got a 25% file size increment where I would have expected a shrink.
Is the RX100 support preliminar? Will it get best with time?

I seldom convert my Nikon DLSR NEF to dng as they reduce in size, but I think I won't convert ARW files that much if that's the state of the art.
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Paolo Avezzano

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Posted 6 years ago

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Paolo Avezzano

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It seems that, despite Sony Raw files are somewhat equal in size no matter what ISO they were shot, DNG converted file grow a lot when increasing ISO.

ISO 125
20,6 MB -> 21,4 MB (0,3 MB of Fast Load Data) = +4%

ISO 3200
20,7 MB -> 28,4 MB (1 MB of Fast Load Data) = +37%

The image is exactly the same: I increased the ISO and reduces shoot time.
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jdv, Champion

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The most recent cut of DNG introduced the fast-load mechanism. I recall this creates a larger file under some circumstances. Sony obviously has some tricks at their disposal for packing more data in. This is not surprising, as they have unfettered and normalized access to binary blobs like the maker notes and so on.

So, when select parts of that data is expanded and reformatted, it is unlikely the resulting file size will have much to do with the original. It will be in the same percentile, probably. But that's about all you could predict.

DNG does not have this luxury, as it is designed primarily to be interchangeable.

Really, though, file-size is the least of your considerations for using DNG. A slight increase shouldn't be a deciding factor to decide if DNG is for you.
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Paolo Avezzano

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Well, an almost +40% in file size -is- a deciding factor, IMHO.

Beside that, the most important issue is in the second post: the big file growth when increasing ISO.
+4% for base ISO settings worths nothing.
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Eric Chan, Camera Raw Engineer

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It turns out this size discrepancy is expected given the differences in encoding between the Sony format and the DNG format.
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Paolo Avezzano

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Is the Sony's ARW the only one to grow a lot when raising ISO setting?
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Eric Chan, Camera Raw Engineer

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No. It isn't directly related to the ISO setting, but instead related to the encoding and quantization scheme used by Sony and how it differs from the encoding scheme used in DNG. (It does get rather technical so I'm not sure I should go into it too much more ...)
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Rob Cole

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Paolo, consider eliminating the preview. Unless you are viewing these DNGs with 3rd party viewers, previews can be omitted. That'll cut the file-size down some...
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Rob Cole

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I'm surprised the preview is so small. I thought at first it was medium vs. high *quality*, but I see now it's medium vs. full *size*. I guess the medium size is small (kbytes-wise). Sorry I can't be more help. I guess it's like Eric said: the Lion's share of it is in the raw encoding... Does beg the question why the DNG compression is so much worse than the ARW compression - no clue... It seems to be OK compared to NEF/CR2.
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Paolo Avezzano

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Exactly, NEF files are always shrank a bit. 10-15% which is not a wide margin, but still better than nothing.
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Eric Chan, Camera Raw Engineer

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The fast load data is not the difference here. (The FLD can take up a bit of space, but it's usually not more than 1/2 MB or so.)
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Rob Cole

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about the size of the new ACR cache entries.
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Eric Chan, Camera Raw Engineer

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The new ACR cache entries (negative cache) are the same format as the fast load data.