dng resulting in a smaller file (rd-1s)

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kchan

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The erf files are about 9.6mb. When I run them though DNG converter the resulting files are smaller, somewhere in the range of 5mb.

Any ideas why?

thanks,
ken
 
kchan said:
The erf files are about 9.6mb. When I run them though DNG converter the resulting files are smaller, somewhere in the range of 5mb.
Click to expand...
The DNG format compresses the the file efficiently in a non-destructive way ("lossless"), i.e. the pixels in the image are not changed in any way.

This is contrast to JPG files, which compress destructively, deleting data to make the file smaller, so some pixels change each time a JPG is resaved.

Some raw files use efficient lossless compression (e.g. Canon 10D CRW files are about 6 MB), others (like Epson ERF) don't. Why some companies don't bother with compression, I don't know: sloppiness!?
 
To compress or not

To compress or not

Compression takes time (processor time). Writing to disk takes time, depending on hardware characteristics. Depending on the balance between these two factors, compression followed by writing small files can be faster than no compression, but writing large files. If the processor in the Rd1s is relatively slow, it may be faster to go for fast writes and no compression. It is not necessarily a sloppy decision, but a value judgement concerning the importance of write/read speed, and amount of storage space. Memory cards are getting cheaper and faster, so the decision by Epson may be wise in the long term. We need to change camera to get a faster processor, but we can upgrade our memory card.
 
The other thing about DNG is that you have a smaller file cause there's no embedded jpeg or side car files...the actual image is as it should be....
 
frncz said:
Compression takes time (processor time). Writing to disk takes time, depending on hardware characteristics. Depending on the balance between these two factors, compression followed by writing small files can be faster than no compression, but writing large files. If the processor in the Rd1s is relatively slow, it may be faster to go for fast writes and no compression. It is not necessarily a sloppy decision, but a value judgement concerning the importance of write/read speed, and amount of storage space. Memory cards are getting cheaper and faster, so the decision by Epson may be wise in the long term. We need to change camera to get a faster processor, but we can upgrade our memory card.
Click to expand...

Some manufacturers, as in the Nikon D2X, let you decide to compress or not compress raw files. According to the D2X manual raw compression can be done with "almost no effect on image quality," but the tradeoff is the extra time it takes to compress. When making the decision to compress or not compress, you also have to wonder exactly what "almost" means. I shoot the D2X in uncompressed raw mode and then convert the result to .DNG in Photoshop. So far I've never been able to detect a difference between a compressed .DNG and its .NEF counterpart -- even at 100%.
 
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Does anyone regularly convert their .ERF files to .DNG as a part of their default workflow? I could see doing that in the interests of space efficiency and compatibility.

just curious...
waldemar
 
waldemarski said:
Does anyone regularly convert their .ERF files to .DNG as a part of their default workflow? I could see doing that in the interests of space efficiency and compatibility.

just curious...
waldemar
Click to expand...

Nope. I convert them to TIFs and use those as a working base. The worked images become JPGs, one in the original (full) size, one in 900x600 (for personal small scale use) and a copy of that one with a watermark for web use.
 
waldemarski said:
Does anyone regularly convert their .ERF files to .DNG as a part of their default workflow? I could see doing that in the interests of space efficiency and compatibility.
Click to expand...

Yup, I do that, and exactly for those reasons. I use two different digital cameras (the R-D 1 and a Nikon DSLR) and I like being able to store the raw files from both in a common format. The fact that the DNGs save some disk space compared to Epson's ERF files is a bonus.

This does lock me out of using Epson's raw file converter, but you have to pick the best compromise for your own needs. If I particularly want the benefits of using the Epson converter (the fact that it generates nice b&w images with little or no need for tweaking, for example) I save the ERF files separately and then run them through the Epson converter.
 
probably trivial sizewise, but your camera specific RAW files may not transfer everything to DNG, usually by design. Not sure about Epson raw files, but Nikon raw files encrypt portions to be used only by Nikon raw editing SW.
 
At first I used the Epson plug-in, but now I convert everything to DNG. One day in the future, Epson's ERF format will become difficult to find software support for, I suspect, whereas DNG is likely to remain around for a while.

Ian
 
I convert everything to DNG and have since it came out....the new M8 actually saves in DNG and I would think that, that will be the norm in the not to distant future....
 
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