DNG file sizes

[FredInMN1]

From a new Leica D-lux 7 the raw files, .RWL, are consistently a bit over 19 mb. Could not open them in Capture One Pro 11.6, so ran them thru the Adobe DNG converter. Those .DNG file sizes are from about 12 to 14+ mb. Would this imply loss of data, or quality of the data, in the conversion process ? Or just a more efficient conversion process ?

Recently found that the ACR in PS Elements 2019 does process the .RWL files so not as much as a concern, but still wondering. Thanks !

 

[Erik Kaffehr]

No, I don't think so...

There are a lot of methods to use bits more efficiently. One such method is Huffman coding but there are more others.

But most of the raw data is garbage, anyway, as there is a lot of statistical noise. So, you can throw away a lot of data but still have all relevant information intact.

Best regards

Erik

 

[Iliah Borg]

Depending on the settings of DNG Converter. If "Use lossy compression" is checked in Preferences, raw data is modified, some raw data (and potentially some information contained in that data, see Mr. Kaffehr's response above) is lost.



Otherwise it is lossless compression, no raw data and no raw information is lost. Some metadata, however, may become unavailable for certain raw converters.

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[FredInMN1]

Thanks for the replies.

Tried converting the same .RWL files with lossy compression 'off' and gave virtually the same sized .DNGs.

 

[Bernard Delley]

Otherwise it is lossless compression, no raw data and no raw information is lost. Some metadata, however, may become unavailable for certain raw converters.

In the case of Nikon, I verified using dcraw -D that the raw data between NEF and DNG are strictly identical. I also found that dng contains more meta data. The size reduction for dng from Nikon files comes that the full size jpg contained in the NEF file is replaced with a much smaller (and less usable) jpg file contained in the dng.

 

[Iliah Borg]

Otherwise it is lossless compression, no raw data and no raw information is lost. Some metadata, however, may become unavailable for certain raw converters.

In the case of Nikon, I verified using dcraw -D that the raw data between NEF and DNG are strictly identical. I also found that dng contains more meta data. The size reduction for dng from Nikon files comes that the full size jpg contained in the NEF file is replaced with a much smaller (and less usable) jpg file contained in the dng.

You can check raw data size directly. For many Nikon bodies, and for some raw recording modes the size difference is because of Adobe using a higher compression. In some cases NEFs are not compressed at all, while DNGs always are.

Metadata size means very little, usability of metadata is what really matters. Try using exiftool on Olympus or Sony files, original ones and DNGs, and compare the outputs from

exiftool -H -S -G -U -a -ee

Availability of white balance tables is one of the things to watch.

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