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08-16-2007, 01:27 PM   #1
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PEF vs. DNG

This may have been discussed before, if that is the case please direct me to the appropriate posting. If not - what is your opinion - PEF vs. DNG??? (K10D)

I use Camera RAW + PS.

Thanks.

Martin

08-16-2007, 01:37 PM   #2
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QuoteOriginally posted by martin s Quote
This may have been discussed before, if that is the case please direct me to the appropriate posting. If not - what is your opinion - PEF vs. DNG??? (K10D)
PEF.

1) PEF is ≈10MB, DNG is ≈16MB.
This means two things:
a) You'll squeeze much more PEFs into your memory card.
b) continuous shooting mode is quicker with PEFs, K10D flushes buffer quicker. DNG needs to write additional 6MB into card and that makes clearing of buffer slower.

2) you can convert PEF into DNG later (if you need), but you can't convert DNG into PEF.
08-16-2007, 01:48 PM   #3
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QuoteOriginally posted by martin s Quote
This may have been discussed before, if that is the case please direct me to the appropriate posting. If not - what is your opinion - PEF vs. DNG??? (K10D)

I use Camera RAW + PS.

Thanks.

Martin
PEF is Pentax version of RAW, and DNG is Adobe's version of RAW. Adobe's goal is to have all manufactures standardize on DNG. Since, I use Adobe Photoshop CS3 and Lightroom as my editors I prefer DNG. All my older RAW files have been converted to DNG.
08-16-2007, 07:11 PM   #4
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QuoteOriginally posted by fwbigd Quote
PEF is Pentax version of RAW, and DNG is Adobe's version of RAW. Adobe's goal is to have all manufactures standardize on DNG. Since, I use Adobe Photoshop CS3 and Lightroom as my editors I prefer DNG. All my older RAW files have been converted to DNG.
I have CS3 and it can read PEF format, is there something CS3 can do in DNG format, but can't in PEF?

08-16-2007, 07:39 PM   #5
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QuoteOriginally posted by martin s Quote
This may have been discussed before, if that is the case please direct me to the appropriate posting. If not - what is your opinion - PEF vs. DNG??? (K10D)
As has already been pointed out, PEF and DNG are both raw formats. I will add only one or two things.

They save exactly the same data. I've talked to an Adobe engineer about this and been assured of this.

PEF is smaller on the SD card not because it's inherently more compact -- it's not -- but because Pentax doesn't compress the DNG files it writes. I'm not sure why they don't, but I would not be surprised if it was simply to provide a slight boost in favor of their own format. Because the PEF files written to the card are smaller, I use PEF while shooting. Once the files are on my computer's hard disk, then I convert to DNG. And after conversion, the DNG files are even smaller than the original PEFs.

I convert to DNG not because there's any real advantage to doing so (well, aside from the fact that the DNG files end up being smaller), but mainly because I suspect, in the long run, DNG is likely to be a more widely support file format than PEF. I am pretty confident that Adobe Lightroom version 5, when it's released, oh, in 2012, will support DNG. Not so sure it will support PEF. Not sure Pentax itself will continue to support PEF.

As for writing to the card, I am not sure there's any difference in speed. I know it seems logical that the larger file should take longer to write, but the file isn't actually LARGER, in the sense that it contains more data. It simply takes up more room on the disk. It does so because it's uncompressed. But I'm not sure that writing to disk actually takes any longer. I certainly have never noticed a difference when I've shot with both formats.

My hope is that, in the near future, Pentax will release a firmware update that will allow us to save files to compressed DNG in the camera. Until they do, I'll save as PEF and convert later.

Will
08-16-2007, 09:42 PM   #6
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QuoteOriginally posted by WMBP Quote
As for writing to the card, I am not sure there's any difference in speed. I know it seems logical that the larger file should take longer to write, but the file isn't actually LARGER, in the sense that it contains more data. It simply takes up more room on the disk. It does so because it's uncompressed. But I'm not sure that writing to disk actually takes any longer. I certainly have never noticed a difference when I've shot with both formats.
Sorry, but it doesn't make sense. File writing time doesn't depend on what is contained in that file, it's purely depends on it's size (in other words: how much space it takes on disk).

10MB vs 16MB means that additional 6MB of data needs to be written in case of DNG. That is 60% overhead. K10D writes onto very fast cards at rate ~10MB/s and that means that PEFs are written onto card in ~1 sec., DNGs in ~1.6 sec. Difference will be even larger in case of slower cards.

However compressing PEF also takes time of course. But it's less than writing additional 6MB into memory card. I tested that just after purchase of K10D. I've made continuous shooting in RAW until buffer filled up and then was taking time how long will it take for K10D to finish writing into card. With PEFs it took significantly less time.
08-16-2007, 10:55 PM   #7
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QuoteOriginally posted by Edvinas Quote
However compressing PEF also takes time of course. But it's less than writing additional 6MB into memory card. I tested that just after purchase of K10D. I've made continuous shooting in RAW until buffer filled up and then was taking time how long will it take for K10D to finish writing into card. With PEFs it took significantly less time.
I'll pass over the matter of what that "additional 6MB of data" you say is in the DNG and just address this point about compression. I think this indeed is an important point, but my experience of it is different from yours.

I just did some tests here, and I repeated each test four times. Shooting with a K10D, manual focus, in continuous mode, I can get off exactly 8 shots in a row saving as PEF before the camera stutters the first time. Saving as DNG, I can get exactly 10 shots off before the camera stutters for the first time. The 10 DNG shots take a fraction of a second longer, but that's not surprising at all, as 10 shots is two shots more than 8. Shooting DNG doesn't capture any less or any more data initially and doesn't make the capture process itself any faster. I repeated these results over and over: exactly 8 shots PEF every time, then the camera balks; exactly 10 shots DNG every time, then the camera balks. The ONLY explanation I can think of for that difference is the overhead caused by compressing the PEFs.

Now, there very well may be variables here, in fact, I suspect that there are. In other words, your mileage may indeed vary. In my initial tests, I was using a 1 GB Lexar 60x card. So I then switched to a SanDisk Extreme III 2GB card and repeated the tests. This time, I got 10 shots off PEF before the stutter, but I got 11 shots DNG off before the stutter -- in other words, the results were pretty similar. Repeated the tests again and again, same results. And once again, the speed with which the shutter clicked was the same regardless of the raw format being used. The difference was in the number of images captured before the camera stumbled.

Be happy to hear from anybody who wants to give this a try. If you want to try it, try to remove as many other variables as possible from the picture. All my tests were done with the camera in manual focus, manual mode with fixed settings and fixed ISO. Don't want the camera having to think about focus or exposure or sensitivity or anything else. Just how many shots can it capture.

Personally, I call it a wash. DNG isn't faster. It just seems to get a couple more shots off in a burst before collapsing. But it isn't slower, either. I will continue to shoot PEF simply because I can get more shots on the card that way.

Will
08-17-2007, 06:06 AM   #8
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I am using Lightroom and when I try to export a photo as DNG, it shows an option for how good a quality imbedded JPEG is going to be. This leads me to believe that DNG stores two copies of an image: raw and JPEG. This actually makes sense to do. Most upscale DSLR's(K10D, D200, 5D) let you store two images of a photo: raw and jpeg. The problem is management: importing pictures into Lightroom, for example, causes doubling of a picture. By keeping JPEG and RAW in one file, makes it much easier to manage.

08-21-2007, 08:17 AM   #9
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QuoteQuote:
I convert to DNG not because there's any real advantage to doing so (well, aside from the fact that the DNG files end up being smaller), but mainly because I suspect, in the long run, DNG is likely to be a more widely support file format than PEF. I am pretty confident that Adobe Lightroom version 5, when it's released, oh, in 2012, will support DNG.
Smaller? I just tried reimporting some .PEF files and the DNGs are half size! You just doubled my storage space! Thankyou! I have to ask, though - why do you copy them to your HDD as DNG first, rather than, say, converting them during import from your card?
08-21-2007, 09:29 AM   #10
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QuoteOriginally posted by agentdeclan Quote
Smaller? I just tried reimporting some .PEF files and the DNGs are half size! You just doubled my storage space! Thankyou! I have to ask, though - why do you copy them to your HDD as DNG first, rather than, say, converting them during import from your card?
I suspect you meant to ask why I copy the files from the SD card to my hard disk as PEF, rather than importing from the card directly into Lightroom and converting to DNG during import.

Answer: Because I've found that, with my system at least, doing this in three steps is more reliable than trying to do everything at once. I was having trouble with Lightroom skipping files during import. Apparently I was not the only person having those problems. May have been a bug that was fixed in the 1.1 release, but I don't care. It's easy to mount the card on the desktop and copy the files there, then open LR and import the files in situ (in other words, leaving them where they are already -- just getting them into LR's catalogue), and as a final step, to select and convert to DNG. Have not had a problem doing this, and really, it takes me no more time.

Will
08-21-2007, 09:41 PM   #11
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Yes that's what I meant...
Thanks for the tip, Will.
Now I have to see if I can get Lightroom to convert my .PEFs to .DNGs but keep all the adjustments I've made. I suspect not.
08-21-2007, 09:44 PM   #12
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QuoteOriginally posted by agentdeclan Quote
Now I have to see if I can get Lightroom to convert my .PEFs to .DNGs but keep all the adjustments I've made. I suspect not.
Yes, it will keep your changes. I do it often, if I forget to convert to DNG before I begin editing.

When you convert to DNG, Adobe simply substitutes the DNG as the new data source for the image. Since the data is identical, just about the only thing that actually changes is the amount of space used on your hard disk.

Will
09-09-2007, 04:13 PM   #13
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I keep reading the PEF to be faster than DNG, but the only review which actually tested this says the right opposite.

"I'll start with the K10D's continuous shooting mode. In JPEG mode, the camera kept shooting at 3 frames/second until I ran out of memory (using a Sandisk Extreme III SD card). In RAW (PEF) mode the camera took ten photos at the same rate before it started slowing down. When shooting in the DNG format the camera took thirteen photos (once again at 3 fps) before slowing down. That extends to RAW+JPEG mode as well, where the K10D took six PEF+JPEG or eight DNG+JPEG photos before hitting the buffer limit. I'm guessing that the added overhead of compressing those PEF files is what causes the speed difference here (DNG files are uncompressed)."

DCRP Review: Pentax K10D

SORRY, WMBP had already corrected these in his second response.

Last edited by pcarfan; 09-09-2007 at 04:27 PM.
09-09-2007, 07:44 PM   #14
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QuoteOriginally posted by Edvinas Quote
Sorry, but it doesn't make sense. File writing time doesn't depend on what is contained in that file, it's purely depends on it's size (in other words: how much space it takes on disk).
Not necessarily true. Compressing data takes time, so it's a matter of "can the image be compressed in less time than it takes to write 6MB of data?"
09-09-2007, 08:55 PM   #15
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QuoteOriginally posted by Edvinas Quote
b) continuous shooting mode is quicker with PEFs, K10D flushes buffer quicker. DNG needs to write additional 6MB into card and that makes clearing of buffer slower.
As others have pointed out, this is NOT true.
DNG RAW buffer clearing time is FASTER than PEF.

This showed that the compression time is more than the time required to write to card for the extra DNG file size.
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