This journal discusses photography in all its guises with an emphasis on the art of making photographs.

One response to “The real capacity of storage cards”

1. Samuli Vahonen

   March 22, 2008 at 4:11 am

   Thomas, the RAW files are packed (lossless packing like zip) and the file size is determined by the content of the file. File size is smaller if any of the condition(s) below is/are true:

   • picture has a lot of smooth out of focus areas
   • lens is not very sharp
   • lens has poor micro contrast (can still be “sharp” – applies to most of Canon lenses)
   • there is not much noise (bigger ISO > bigger RAW file size)
   • too small aperture (f/11 or smaller) is used and diffraction eats all the small details in photo
   • tripod (and flash) is not used (traditional rule 1/focal length does not work if you want every pixel to be sharp, this is based on ancient sharpness requirements with film and small print size. The circle of confusion is about 0.3 etc. which does not apply if you print larger than A4/Letter size)
   • even very slight focus errors will cause softness causing smaller file size (micro focus adjustment on 1D Mark III is really good to have knowing quality control of Canon lenses).

   I have never got more than 16MB files from Canon lenses when using ISO 100 with 5D but for Example Carl Zeiss Distagon T* 2.8/28 constantly produces files which size is over 19MB, and sometimes file size gets to 22MB. Also difference in large prints (e.g. 75cm x 50cm / 30″ x 20″) you really can see the difference between Carl Zeiss and Leica lenses compared to Canon lenses. Canon lenses are optimized to produce big contrast but they are really poor in micro contrast and small details. Of the lenses that you have only the Canon EF 200mm f/2.8 L has decent micro contrast; you may end up with a file size close to 16MB if you take a photo in which everything is inside DOF, there is a lot of detail and a tripod is used.

   Also it seems that the anti-alias filter has something to do with this: I switched to the Canon 1D Mark III and even though it has 2.5 fewer megapixels yet the file size is quite close to the 5D’s file size. Also due to live view and exact focusing I get more constant results with manual focusing and I no longer need to focus bracket to get excellent results.