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photo:raw

digital camera RAW files

introduction:

  • digital photography RAW files are the files that most cameras can output and allow to be saved on your memory card or computer which contain the raw digital data derived from the sensor with usually no image processing performed on the file but with added metadata stored within the file relating to the camera used, time, date, settings used (such as white balance, shutter, aperture, ISO) and in some cameras, GPS location data.
  • you cannot view the image of a RAW file without it first being processed by a RAW converter software.
  • unfortunately each camera manufacturer has its own proprietary formatting of the RAW file and this changes with each model they put out which usually means when you buy a new camera, you will need to update your RAW converter software (fortunately, when you buy the camera it usually comes with the manufacturer's version of RAW conversion software included to get you started).
  • RAW files tend to be quite large (10-20Mb is common for 10 mpixel cameras), although some manufacturers have smaller files due to lossless compression of the RAW files.

advantages of RAW files:

  • altering white balance is significantly easier and as it is in 12-14bit space rather than jpeg's 8 bit space gives better results.
  • the 12bit or 14bit data space of RAW files allows each pixel to have 4,096 or 16,384 brightness levels instead of only 256 as in a 8 bit jpg
    • this means MUCH better images IF you are going to do significant post-processing which may cause excessive posterisation effect if using only 8 bit data (you can see this in the final histogram as being jagged points instead of smooth curves)
  • RAW files hold more highlight data and thus allow errors in exposure to be more readily corrected as well has high contrast scenes better able to be post-processed. Thus blown highlights can be corrected more effectively although perhaps not completely.
  • as it holds all the RAW data, even better quality images may be obtainable in the future as RAW conversion software improves.
  • some manufacturers allow an alternative smaller RAW file which converts into a lower resolution image than the full RAW file (eg. Canon's “sRAW” file - although this is of dubious benefit but may be useful for action photographers who want to post-process their rapid burst images and are not so concerned with image resolution. 
  • as an attempt at creating a generic RAW file format which hopefully will be more likely to be accessible in the future, Adobe have created their RAW file format called DNG, so many users convert their original proprietary RAW files to DNG format.
  • each manufacturer tends to use their own file extension name for their RAW files:
  • Adobe: .dng - also can be created in camera by Pentax K10D, Leica M8, Hasselblad H2D, Samsung pro 815.
  • Olympus: .orf
  • Panasonic: .RW2
  • Canon: .crw
  • Nikon: .nef

RAW file processing software:

  • manufacturer's proprietary software - often limited capabilities and of course only does the one format:
    • Olympus:
      • Olympus Camedia Master - limited development options but good quality
    • Canon:
      • Canon ZoomBrowser EX with Raw Image Task
    • Nikon:
      •  
  • Adobe Photoshop:
    • uses Adobe Camera RAW (ACR) plug-in, the latest version of which can be downloaded for free (it's almost impossible to find the last updates for PS2 or earlier though).
    • this is installed in the FileFormats folder under Plug-Ins & is called Camera Raw.8BI 
    • development options such as adjusting the histogram curve, correcting for vignetting, etc.
    • unfortunately, Adobe tends to force you to upgrade to their latest Photoshop version by not making the Camera Raw plug-in updated for previous Photoshop versions - hence for new cameras, you now need to buy Photoshop CS/3 as CS/2 will not work for RAW conversions.
    • ACR v2.3 and higher supports DNG format
    • version 2.4 for CS - does not do Canon 350D, 5D, Olympus E500 and others
    • version 3.x for CS2  - does not do 2007 dSLRs such as Canon 1D Mark III
    • ACR v4 and higher is not compatible with PS CS, CS2 or earlier.
    • some manufacturers also provide their own Photoshop plugin but this tends to use a different interface in Photoshop than PS's Camera Raw plug-in:
        • this file is called ORF Import.8ba and installs in the Import-Exports folder under Plug-Ins
        • access via File:Import:Olympus RAW on the menu
        • not as many options as the Adobe RAW plugin, as only can change:
          • exposure compensation, WB with gray point specification, contrast, sharpness, saturation, & color space.
          • no histogram displayed, by default creates a 16 bit image.
          • slower to process. 
  • Adobe Lightroom:
    • designed specifically for photographers to improve their digital workflow
    • supports DNG format
    • faster than Bibble v4, but Noise Ninja not included
    • v1.0 supports same cameras as ACR v4.0
    • v1.1 supports same cameras as ACR v4.1
    • freeware using DCRAW but with some nice processing algorithms
    • freeware but no EXIF info, colour management, zooming or cropping
  • RAW Developer:
    • Pro version costs $US499 - this is what most professionals seem to use (LE version for $US99)
    • still doesn't support Olympus E510 or Canon 1D Mark III (as of June 2007)
    • complex, includes Noise Ninja
    •  
    • free; as good or (even better) as PSCS except that it doesn't have the chromatic aberrations correction.
    • bought by Adobe so no longer available.
  • dedicated astrophotography software:
  • see also on the web:
photo/raw.txt · Last modified: 2011/09/26 21:32 by gary