RAW: Compressed versus Non-Compressed

Discussion in 'General Technical Discussion' started by fotographik, Jul 30, 2007.

  1. This may very well be a stupid question but here goes:

    The D200 allows me to save files that are either RAW or compressed RAW. Is that compression lossless? If it is lossless, are there any known drawbacks or advantages to using the compressed NEF format? (I'm presuming it would take a bit longer to write the file to the CF card due to the "compressing".)
     
  2. Baywing

    Baywing

    Feb 22, 2005
    CT USA
    I don't recall much about the D200, I had one for 6 months and that was over a year ago. However, I still have the D100 which has the same options. Compressed RAW, in theory, results in smaller file sizes, which should in turn, write faster, but that is tempered by the extra processing time. You can check the relative speeds very easily. Take 5 shots (continuous high, ie, fill the buffer) and time how long it takes to write. Try each mode, you'll see which one is the faster. With the D100, compressed RAW takes forever and a day....
    There have been MANY discussions as to whether compressions are lossy, I think they all are from an absolute point of view. From a practical point of view, you won't likely be missing much, as the compressed areas are usually sky. I normally shoot my D2x in large, fine jpeg with compression set for optimum quality. I get great 20x30's and have the added benefit of more buffer, which I need for my style of shooting.
    In the end, it's your choice which setting works best for your style, and that choice is made easier today by the lower costs of flash memory.
     
  3. I shoot everything on my D2x in compressed RAW and have not noticed any difference in images.. I also tried shooting in uncompressed RAW and compared the two.. I could not see any difference...
     
  4. Thank you both for your input. I appreciate it!
     
  5. Francois,

    I shoot compressed RAW almost exclusively, it gives me extra room on my storage card (about double uncompressed) due to the smaller file sizes.

    The loss that occurs is at the higher range (in other words whites) of the image, so it if you are frequently over exposing, you will have less data to pull back. Depending on your style, this may or may not be important to you.

    Nikon states that it is virtually lossless, but there is some loss of data.

    I haven't compared the write times in the camera, given that with the D200 it takes quite a few shots to fill the buffer, and frequently (but not always), the buffer clears befores the sequence is over.
     
  6. Thanks for the info Mark. Time for me to go out and experiment to see how it affects the whites!
     
  7. I could see the need for compressed RAW when the CP cards were only one Gig and cost a fortune. Now that the price has dropped and the capacity has quadrupled--probably more by the time I finish this message, why worry about it. It's the old story with computers; in the bad old days, memory was expensive and programmers' time was cheap so programs were tight and small; now memory's cheap and programmers aren't so we see bloated programs.

    Nikon says compressed RAW is "virtually" lossless but it has to lose something to be compressed--I've been through the argument many times before about how significant or not this is but in an area where people argue over the difference between the f1:4 and f1:8 models of a similar lens, why would we put up with any loss at the beginning of a series of losses as we go through the post-processing stages?

    Bruce
     
  8. You bring up a good point Bruce...CF cards are not all that expensive anymore so I won't worry about using the larger un-compressed NEFs. I played with the two formats a bit yesterday and (to me anyways) it's not worth hassling with.
     
  9. Bruce,

    True, cards are cheap, and they are reusable. The other factor to consider, which may or may not be an issue, is download speed from card to computer, plus storage.

    The compressed RAW files are typically about half the size of the uncompressed, so the flip of the larger file size is more storage requirements (which are also getting cheaper per GB).

    Best part is, you get great images no matter which.
     
  10. I seem to recall that the D100 had glacial write speed with compressed RAW.
     
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