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Personally, I shoot in DNG and avoid the proprietary RAW format for my camera (PEF on a Pentax K200D). I like DNG because it's open and supports embedded metadata, both of which is not true with formats like PEF (Pentax), NEF (Nikon) and CRW (Canon). What are the incentives for shooting in these proprietary formats then?

Clarification: My question is not really about converting the RAW format of the camera into DNG as a part of a workflow (during post processing or importing, say) but rather if the camera supports shooting both RAW and DNG then why stick with RAW.

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Maybe it is just me, but this question sounds a lot like some sort of DNG astroturf. Perhaps it could be reworded to be a little less biased towards DNG, which is not even an option on 99% of cameras out there. Perhaps it would be helpful if you listed some more reasons DNG works better for you, other than philosophical objections to proprietary formats? For example, if I use software that manages side-car files, why do I care about them? –  Josh Goldshlag Jul 18 '10 at 1:27
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I didn't mean to have it come across as astroturfing. I prefer DNG for the moment and thought it might be a good question to ask about the advantages of other formats compared to DNG. –  Jonathon Watney Jul 18 '10 at 7:15
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What recent changes? –  Dave Van den Eynde Aug 4 at 11:26
    
I assume software have gone through a development the last 4 years. Several of the arguments are based on software support for DNG. –  Håkon K. Olafsen Aug 5 at 7:34
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These answers seem sufficiently current to me. –  Reid Aug 5 at 16:30

9 Answers 9

The biggest advantage to me, is that it's an extra step in my workflow to convert my 5D2 raw files to DNG. That extra step translates into more time in the post processing step. I'm going through 20GB of photos I just took while in spain, and converting them to DNG before I got started with it, would be a pain. I could save the resultant images as DNG, or have Lightroom convert to DNG upon import, but that still is more time that doesn't translate into any percieved benefit (since Lightroom already manages the metadata for me).

If my camera could shoot DNG natively, then perhaps I would consider shooting DNG.

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Ah, I see. So not all cameras support DNG in camera. That makes sense. Perhaps a list of cameras that support DNG would be useful? photo.stackexchange.com/questions/762/… –  Jonathon Watney Jul 17 '10 at 22:21
    
I always convert to DNG during import to Lightroom. It does take a bit longer - but once I click on import, I go to make a coffee and when I get back the import & DNG convert is done, so I don't really notice the extra time (not that I have the option of shooting in DNG) –  Wilka Jul 18 '10 at 7:23

I guess technically speaking, DNG (although it is called a raw file or raw file archive) is not really raw in the truest sense. A "RAW" file is one that is essentially a direct dump of data from a camera's image sensor and image processors (i.e. Digic 4 in Canon), without any format conversion or processing applied. Such raw files are tuned to the hardware for optimal performance, and as such are unique to the hardware they are written by. Thats why each camera manufacturer has their own format. Saving to DNG within a camera would require conversion from the cameras native raw file format into DNG.

The advantages of a true RAW format over a DNG are probably limited. If you photograph action a lot, and use a high frame rate camera like Canon 1D series or the Nikon D3 series, shooting in the camera's native raw format will likely get you a higher FPS vs. shooting in DNG (if it is supported), since you eliminate the need to convert. If a high frame rate is not important, shooting directly to DNG is probably beneficial as it can shorten your import times for post processing.

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I think the bottleneck limiting FPS is usually the speed of writing to the card rather than conversion (this is why you can often get higher FPS with JPEG even though it requires more processing). –  Reid Jul 18 '10 at 1:50
    
@Reid: JPEG writes faster since it is a compressed format. Comparing raw to raw, the native format of a camera, while it will still write considerably slower than JPEG, will likely write faster than DNG when you add in the conversion since they are both large files. –  jrista Jul 18 '10 at 2:07
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I convert my Canon CRW files to DNG and get a 20% reduction in file size, so maybe you would get a faster shooting rate with DNG ...? –  Hamish Downer Jul 18 '10 at 14:39
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@Hamish: I guess the CRW format is less efficient? I've noticed that my .CR2 files tend to be smaller or the same size as my .DNG files. I would kind of expect that, as the DNG contains additional information. But, good point...if the DNG is significantly smaller than the native raw, it would likely write faster. However, in general, one should expect the files to be very similar in size. –  jrista Jul 18 '10 at 19:00
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DNG files can do additional lossless compression, which would take a (small, but) considerable amount of time to do in-camera, giving that camera an unfavorable disadvantage against competitors in terms of speed versus the amount of space saved. –  Dave Van den Eynde Jul 20 '10 at 11:17

There's one particular difference that I'm aware of: proprietary RAW formats contain complete data, while the DNG standard has a specific format, which may not match up to a RAW format. I'm aware some vendors, Nikon in particular, have been encrypting some of their RAW data so that it cannot easily be converted, if at all.

As requested, I found a source from my bookmarks regarding the encryption issue. Following is a quote from a forum posting I'm unable to find at the moment. Text is copied from http://www.photoshopnews.com/2005/04/17/nikon-d2x-white-balance-encryption/:

They (Nikon) decided to ENCRYPT the white balance data inside the NEF file for these cameras. Previously, the white balance data was stored in non-encrypted format, and was readable to third party raw converters using simple reverse engineering of the file format.

Referring to the D2X and D2Hs; the blog post is from April 2005, for what it's worth. It may have since changed - haven't been following the issue, I just use NEF - but it was a concern at the time.

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Do you have a source for these claims? This is a very strong argument against DNG, but should be backed up by reference(s). –  Håkon K. Olafsen Aug 5 at 7:41

Another advantage is that the manufacturer's raw files are better supported by post-processing software. For example, the raw converter I use, Bibble, supports basically all Nikon DSLRs and add support for new models quickly. The way they do this is to obtain raw files from each camera and test those and tweak as necessary. This is done using NEF, not DNG. Thus, for any given camera, the data flow from sensor to JPEG is better tested if it does not include DNG.

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Here's Thom Hogan's take on DNG. He feels pretty much the same way I do. bythom.com/dng.htm –  Reid Jul 18 '10 at 3:04
    
So why wouldn't Bibble also test the chain for DNG-pictures? Not sure I buy your argument. –  Håkon K. Olafsen Aug 5 at 7:40
    
Well, for one it would double their testing workload, since the number of formats per camera is doubled. –  Reid Aug 5 at 16:27
    
Since DNG is a standardised format (the whole idea), it would only add one test file to their test suite. –  Håkon K. Olafsen Aug 5 at 18:25
    
No it would not. You cannot assume that the standard is implemented correctly across all camera conversions. You need to test each one. –  Reid Aug 5 at 19:41

There is something particularly conceptually wrong with throwing away the stuff that comes out of your camera. If your camera shoots in DNG, then that's what you work with. If it shoots in RAW, the same. If it shoots in either, you have to figure out what the difference is in terms of metadata that is supported, as well as all of your workflow.

When your camera shoots in its own proprietary RAW format, and you convert that into DNG and throw away the former, you're essentially throwing something away and the sad part is that you probably don't even know what. It's like shooting in color negative film, and have the lab contact print that into color positive film, just because you're scared that someday your scanner will no longer scan negative film anymore.

If your workflow supports your proprietary format today, there is no reason to think that it won't support it tomorrow. So what is the net benefit of converting it into another proprietary format that is simply 'open' because Adobe has published the specs? That whole open/closed thing doesn't matter. What matters is the tools that you use and how they support them.

I've made the mistake of converting and throwing away the originals, and I did learn the hard way. I didn't lose any shots, but I lost my freedom to use them in the tools that I wanted, because those tools didn't support the DNG as much as I wanted to.

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I like your argument. But what do you think about the "all formats become obsolete"? I'm not sure it's an argument for or against either DNG or any proprietary format. I can still get my grandfathers WWII era film negatives developed at a cost, but I the digital world seems to move faster with little regard to backward compatibility... How much pain is it to open wordperfect documents or lotus 123 spreadsheets. Will RAW files be as hard to read in 20 years? –  beggs Jul 20 '10 at 9:21
    
I don't know how much pain it is to open WordPerfect documents or Lotus 123 spreadsheets. Even though I can't buy WordPerfect anymore (not the original DOS version, anyway) I can still open them fine in MS Word 2007. Will RAW files be hard to read in 20 years? Who knows? I can still open 20 year old GIF and PCX files. Besides, I don't know if you can still get your grandfathers era film negatives developed. Some film processes are no longer available, because of environmental issues with the chemicals, or simply because they are no longer commercially viable. –  Dave Van den Eynde Jul 20 '10 at 11:14
    
I believe there's an option to embed the original RAW file in DNG in case you want to extract it later. However, if you camera doesn't support writing compressed DNG natively, I'd probably wait. Otherwise, I'd convert to be future proof. –  Eruditass Jul 27 '10 at 3:59
    
just as an aside, yes, essentially all film ever made can still be developed with existing methods, at least to produce a black-and-white negative, as all film processes rely on silver halides for their initial latent image. E.g., if you find a roll of Kodachrome sometime after processing is discontinued in December 2010, that will be one of your options. –  ex-ms Aug 4 '10 at 19:19
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DNG always struck me as a solution in search of a problem. I can't think of a situation where it would make sense to use it even in-camera since the conversion from having all the data to only the bits that DNG supports is still a step away from having the raw data (the point of capturing the raw file in the first place). –  James Snell Aug 4 at 10:38

Losing the manufacturer-native RAW file feels akin to throwing away negatives just because you have some prints (okay, it's not that bad).

It seems logical that camera manufacturers are in a position know their cameras, their lenses, their systems, best. Though DNG is extensible, it's not controlled by camera manufacturers, and innovations they implement may conceivably not be easily reflected in DNG. They could, on the other hand, more easily extend their own RAW format(s). On the other hand, if they were constrained by DNG, it could conceivably stifle innovation. Is DNG always good enough for everything? Or is DNG just better for Adobe?

What if DNG becomes a standard and needs to be extended to support a new feature Canon rolls out, but Nikon has more sway with the standards board? Or maybe Canon wants to keep it proprietary? DNG breaks down and everyone's using their own formats again, and DNG. You'd have been better off just using a camera-native RAW format all along.

As for workflow, i'd support conversion to DNG if it makes software better, but if my Nikon saves its best image as NEF, you can be sure i'm saving that NEF file, even if i convert to DNG. If my next Nikon spits out DNG files, i will only opt for that if i can't get a NEF from it.

If your Pentax does both, i'd stick with the PEF file. If you use DNG in your workflow and have card space to burn and you'd rather have the camera do the DNG conversion in-camera, take advantage of that and save both. But throw away the PEF file? No way. What if your next Pentax doesn't save DNG? What if DNG eventually goes away? Will you some day kick yourself for not having that PEF?

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Your last paragraph doesn't make sense at all. If my next Pentax doesn't save DNG, then it doesn't save DNG. I still have my old Pentax's DNGs that will always be readable alongside my new proprietary PEFs. –  erjiang Jun 15 '11 at 14:28

Note: For your particular case where your camera actually shoots in DNG there's no reason not to use it as that IS the RAW format of your camera anyway. Note the definition of DNG is Digital Negative (DNG): an open lossless raw image format. That is, DNG is also a RAW format.

While there're very strong arguments about DNG VS RAW let me summarize a couple of things from the practical point of view:

DNG is a better format 99% of the time. Original RAW is only important if you are using propietary editing tools (like nikon capture nx 2, for example) or if you're going to participate in a contest (or forsee that you may) that requires you to provide the original RAW. Even in those cases I would recomend using DNG with the original RAW embedded in the DNG.

What we sometimes forget is that the RAW image is not the final image, the only value it really has is to provide authenticity to the photo if that is required. The RAW file is equivalent to the negative, you have to develop it for it to have real value. What has value are the final images that you can extract from that RAW file, and for that I've never been able to notice any difference between developing the file from RAW or from transformed DNG.

Against what is usually believed, DNG is not an Adobe format, is an open RAW format created by Adobe, but it's open, which means the information about the format is available to everyone, unlike propietary formats which are usually revered engineer.

This has a couple of implications:

  1. If you're using independent software (i.e. not your camera manufacturer software) they're doing a conversion anyway from the original RAW to something they can understand. As far as I know none (or at least not the most used programs) work directly with RAWs, they interpret the information and then store the changes in different formats. That means if you're using Camera Raw or Lightroom to edit your images, working with the original RAW posts no benefits.
  2. When you transform your RAW to DNG some information is lost, however, once again, if you're using some of the most used comercial tools (basically anything that is not your camera manufacturer software), the information that is thrown away anyway is information that can't be used by the software in any case... and the information that is thrown away is never part of the information that conforms the image.
  3. Some photography contests require you to provide the original RAW file and DNGs are not valid unless that's the native format of your camera. That's a point to take into account and if you feel a photo may be contest worthy you should emb the original RAW into the DNG.
  4. DNGs are smaller, which translate in less space used and faster load times in most programs.
  5. There's the theoretical possibility that some of the information of your RAW that Photoshop doesn't understand today, turns out to be used in a future version of Photoshop and by converting it to DNG you lose it. This is a really slight possibility.
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Downvote - There is no evidence to support the assertion this answer is based on (that DNG is better than RAW.) You may prefer it and you may have reasons why but that's different. –  James Snell Aug 4 at 10:35
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I've explained two reasons why I consider DNG is better than RAW. Specification is open and it's smaller which results in less space used and faster processing. You may disagree but don't tell me there's "no evidence" –  Jorge Córdoba Aug 4 at 10:41
    
@JorgeCórdoba I have personal experience that the reverse is true. At the time, DxO did not want to read DNGs because they don't support it. In their own words: "DxO has never supported DNG files as an input option. DNG files have had their EXIF altered, and our program can not read altered EXIFs because they change the critical information needed to make our program able to do the corrections that it can do." –  Dave Van den Eynde Aug 7 at 8:19
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You can find more information and debate about that particular issue with DxO here: photo.net/digital-darkroom-forum/00bj5j but basically, if a given provider refuses to accept a file that's a completely different topic. If they'd say they won't open jpg because it's compressed and they lose quality that their right, but it's commercial reasons, not technical reasons... –  Jorge Córdoba Aug 7 at 8:23

Whether there is any benefit of shooting in the proprietary format depends on the particular implementation of the two raw formats by the manufacturer. For example, is the DNG format storing the same metadata? Is it using lossless compression? If the files give identical results and contain identical metadata, then it might be beneficial (more future proof) to shoot DNG in camera.

That having said, one of my cameras shoots DNG only. When importing to Lightroom, I still let it "convert" to DNG. When the file is processed this way, LR adds fast load data and some other information that makes it easier to edit the files. So in my case the workflow and processing time is the same as with camera that stores only proprietary format.

To sum it up, I would compare the outputs for quality and metadata. If there is no difference, I would shoot DNG. If there is difference, I would shoot the format that gives better results and makes the camera more happy. I would convert to DNG in Lightroom anyways. My workflow is based on LR, YMMV.

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Since my other answer (while popular) is not really an answer to the question, I'll go ahead and post the right answer.

If your camera shoots in DNG 'natively', then I would go ahead and go with DNG, because it's what the manufacturer adopted as its 'raw' format. It will contain every bit of information the camera can produce. I believe that this is what Leica is doing, but I'm not sure.

If your camera offers both DNG and their own 'proprietary' RAW format, then I'd consider using the proprietary format if your workflow allows it. In my case, if LR would support the raw format I'd use that. You have to wonder what advantage the camera manufacturer saw in supporting its own proprietary format in addition to DNG and my suspicion would be that it couldn't contain all the bits of information they wanted or in a format they wanted or the software just omitted some bits out of lack of time to implement it.

If you're worried that your proprietary format may one day be no longer readable, convert to DNG but for the love of god and all that is holy do not throw away the originals.

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