One of my students was telling me that she had recently read an item which stated the archival properties of jpgs were not as good as RAW format.
In researching I haven't been able to find anything on archival standards. Most comments on RAW archiving seem to centre around whether current RAW standards will be supported in future software development as opposed to how long an image might last in either format.
Can anybody shed some light on this?
Posted by David Bostedo on October 17, 2008 at 7:18 PM
Well Dave - either way you're guessing that one format will survive the other. In this case, jpg has been a more universal standard, so it's likely to outlive any RAW format. The other thing is, RAW is usually proprietary, and JPG (and I suppose DNG) are open stadards, so someone could always write new software to support them without reverse engineering anything.
...opposed to how long an image might last in either format.
I'm not sure what you mean by this - do you mean physically on a disk? It's possible that one format or another could be robust in terms of recovering from corruption that may occur over a long time on a disk; But I don't know why JPGs wouldn't be better in this regard too, for the same reasons as above, with one caveat. Maybe because JPGs are compressed in a lossy manner they're harder to recover? (Like a bit error in JPG could take out a whole section of the image, where a single bit error in RAW might only corrupt that one bit?)
I don't quite know enough about JPG compression to make a definitive statement, but JPG compression does depend on blocks of pixels.
David is right, but lossless formats like DNG or TIFF are still better options than a lossy format like JPG and are open/universal, as opposed to proprietary raw formats.
As I understood the student's comments it was that with all conditions being the same, medium, storage environment etc. a jpg image would not have the same longevity as a RAW image. It does seem to make sense that a lossy format might have something to do with that.
On the longevity issue. JPG's are a lossy file. The longer you store it, the more lossy it gets.
David, these are 1's and 0's stored on a disk or some other media. A 1 and a 0 is no different between jpg and raw. If you are going to lose 1's and 0's in one format, you are going to lose them in the other format if "all conditions being the same". The only sane thing I read above is that if you lost a single bit in a RAW file, you lose a bit or pixel maybe, while it would be more damaging to the jpg format. I can buy that. Once a file loses it's checksum, the whole file may be corrupted.
I personally store three copies - the original untouched file, a tiff file, and a jpg file. Depending on what I want later with the file, I select the proper file and don't have to go retouch anything. It's there ready to go. And if I want to start all over, the original is right there, too. All have the same same filename with different extensions. So, if I search for them, they all pop up together.
If the student thinks jpg's will vaporize before raw, I wonder which word processor and spreadsheet format he thinks will outlast the others before vaporizing off the disk?
Troup
Posted by James Hersey on October 18, 2008 at 11:38 AM
I vote for the RAW or DNG for archiving but on images that have taken a lot of post capture work I save a tiff (master) along with the RAW. One reason for saving the RAW/DNG as digital raw conversion technology changes you may be able to get more from a RAW image in the future than you can today. I feel I can get better conversion with CS3 or lightroom of my first digital raw files for a 10D than I was getting form the conversions I had then. I don't use DNG at this point but as I see the loss of RAW conversions for a file format I have then a conversion to DNG would be required. As for that matter it might mean converting for CD's to a newer format to store the images should CD's be left out in the future. I use hard dives and CD's at this time.
I have done the same thing as James, gone back to old RAW files and remastered them, due to both the superiority of ACR in CS3, and because I have gained in knowledge.
Discussion
6 repliesIn researching I haven't been able to find anything on archival standards. Most comments on RAW archiving seem to centre around whether current RAW standards will be supported in future software development as opposed to how long an image might last in either format.
Can anybody shed some light on this?
I'm not sure what you mean by this - do you mean physically on a disk? It's possible that one format or another could be robust in terms of recovering from corruption that may occur over a long time on a disk; But I don't know why JPGs wouldn't be better in this regard too, for the same reasons as above, with one caveat. Maybe because JPGs are compressed in a lossy manner they're harder to recover? (Like a bit error in JPG could take out a whole section of the image, where a single bit error in RAW might only corrupt that one bit?)
I don't quite know enough about JPG compression to make a definitive statement, but JPG compression does depend on blocks of pixels.
Guy
As I understood the student's comments it was that with all conditions being the same, medium, storage environment etc. a jpg image would not have the same longevity as a RAW image. It does seem to make sense that a lossy format might have something to do with that.
David, these are 1's and 0's stored on a disk or some other media. A 1 and a 0 is no different between jpg and raw. If you are going to lose 1's and 0's in one format, you are going to lose them in the other format if "all conditions being the same". The only sane thing I read above is that if you lost a single bit in a RAW file, you lose a bit or pixel maybe, while it would be more damaging to the jpg format. I can buy that. Once a file loses it's checksum, the whole file may be corrupted.
I personally store three copies - the original untouched file, a tiff file, and a jpg file. Depending on what I want later with the file, I select the proper file and don't have to go retouch anything. It's there ready to go. And if I want to start all over, the original is right there, too. All have the same same filename with different extensions. So, if I search for them, they all pop up together.
If the student thinks jpg's will vaporize before raw, I wonder which word processor and spreadsheet format he thinks will outlast the others before vaporizing off the disk?
Troup