How do I know what primes to buy?

I’m a big advocate of prime lenses in place of zooms.  But if you’re not sure which focal lengths you use the most, here’s a way to find out:  Extract the EXIF data from your images, find the FocalLength entry, and count the number of occurrences of each focal length:

$ sort /tmp/index | uniq -c | sort -nr
     33    exif:FocalLength="18/1"
     12    exif:FocalLength="55/1"
      6    exif:FocalLength="24/1"
      6    exif:FocalLength="23/1"
      6    exif:FocalLength="21/1"
      4    exif:FocalLength="27/1"
      4    exif:FocalLength="25/1"
      4    exif:FocalLength="20/1"
      3    exif:FocalLength="50/1"
      3    exif:FocalLength="40/1"
      3    exif:FocalLength="29/1"
      2    exif:FocalLength="44/1"
      2    exif:FocalLength="37/1"
      2    exif:FocalLength="34/1"
      2    exif:FocalLength="30/1"
      2    exif:FocalLength="28/1"
      1    exif:FocalLength="53/1"
      1    exif:FocalLength="46/1"
      1    exif:FocalLength="45/1"
      1    exif:FocalLength="36/1"
      1    exif:FocalLength="35/1"
      1    exif:FocalLength="33/1"

From this, I see that I use 18mm, 55mm, 24mm, 20mm, and 28mm the mose, in that order. So I’d be looking at 18mm, 50mm, and 24mm primes soonest.

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  1. #1 by Joshua on July 19, 2012 - 6:02 PM

    And 35mm after that.

  2. #2 by Joshua on July 19, 2012 - 6:33 PM

    Here’s how the above data breaks down when rounded to the nearest prime focal length:
    18mm – 33
    50mm – 18
    24mm – 16
    20mm – 10
    28mm – 9
    35mm – 6

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