Espon RAW vs. Adobe DNG - size difference

[triplefinger]

Howdy, I'm wondering if anyone here may know...

I recently purchased (and already love dearly) an R-D1, whose RAW file format is *.ERF and I have been converting the files to *.DNG for easier processing...

the ERF version of the file is MUCH larger than it's DNG counterpart, for example my shot #erf1800.erf = 9.5 mb but #erf1800.dng = 3.8 mb

has anyone seen or done a side-by-side RAW test, or could be be just the way the data is organized? or does maybe the DNG conversion refer back to the ERF(meaning I should NOT delete the ERF, so as to render the DNG worthless?)

to me, on an old power book, the files look the same.

Thanks for any input. Mike

 

[kbg32]

As far as I know, it is all in how the files are compressed. ERFs are proprietary Epson RAW camera data files and can only be opened by either Epson proprietary software or any other program that can identify and open them. DNGs are a public archival format for digital camera RAW data. DNGs are trying to become an open standard that can be recognized and open by a variety of RAW processing programs that can identify them as well. Not every RAW data file can be opened by just any software. DNGs were created in the hope that they would be adopted by camera and software manufacturers as an open standard.

 

[jlw]

The files look the same to me, too, at least when opened by Adobe applications such as Camera Raw or Lightroom. DNG files are a variant of the TIFF 4.0 specification, which includes the capability of using lossless "LZW" compression -- I suspect this is the main reason they can be a bit smaller than the raw files they represent.

It's possible that other conversion applications might render ERFs and DNGs with somewhat more visible differences. Personally, that possibility doesn't worry me enough to make me want to archive the ERFs as well as DNGs, but if you're really the belt-and-suspenders type, you might want to save both.

It IS possible, using the options in Adobe DNG Converter, to "encapsulate" the original raw file within the DNG file, making it possible to extract it again later in case you want to standardize on DNG but still have the option of using Epson's raw converter on the files. Encapsulated raw files are larger than either a DNG or an ERF file, but I think they're still smaller than the combined total size of a DNG and and ERF file. This might be a good compromise if being able to get back to the original ERF makes you feel safer.




(Incidentally, in case anyone is curious: "LZW" stands for Lempel, Ziv and Welch, the three people who developed this compression method.)

 

[Innerimager]

The DNG files are already compressed from 14 bit to 8 bit in camera. This was discovered by users and at first gave concern, as it would seem that dynamic range and ability to manipulate the data without artifacts would be a problem. But, it seems Leica came up with an excellent process that preserves files with great depth and workability while greatly reducing their size, with obvious benefits. The Epson Raw files are probably 12 or 14 bit, and thus much larger despite less megapixels. best....Peter

 

[pfogle]

The DNG files are already compressed from 14 bit to 8 bit in camera. This was discovered by users and at first gave concern, as it would seem that dynamic range and ability to manipulate the data without artifacts would be a problem. But, it seems Leica came up with an excellent process that preserves files with great depth and workability while greatly reducing their size, with obvious benefits. The Epson Raw files are probably 12 or 14 bit, and thus much larger despite less megapixels. best....Peter

AFAIK the 8 bit files only apply to Leica M8 files, where an in-camera gamma curve allows the shadow detail to be retained while limiting the color depth to 8 bit.

The Epson files are 12 bit.

I think the DNG files from ERF are 12 bit, but compressed. I may be wrong...

 

[triplefinger]

know this stuff, is it advisable to work from the original epson files? or are both a good starting point?

Thanks

 

[jlw]

know this stuff, is it advisable to work from the original epson files? or are both a good starting point?

My experience is that I get equally good results starting with ERF or DNG files. As I noted in my first post, I use Adobe applications (Camera Raw or Lightroom) to render these files.

If you used a different converter application, it's possible that you might see slight differences depending on how the converter interprets the two file formats. Only you can make that decision.