So an analysis of which focal lengths are used how often is quite easy:
$ exiv2 -g Exif.Photo.FocalLength *CR2 | cut -b 82- | uniq | sort -n | uniq -c
4 24.0 mm
1 27.0 mm
1 28.0 mm
1 34.0 mm
3 35.0 mm
1 45.0 mm
1 48.0 mm
6 50.0 mm
8 70.0 mm
1 85.0 mm
1 97.0 mm
1 127.0 mm
1 135.0 mm
1 173.0 mm
7 200.0 mm
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