I am getting the wrong exif value for ISOSpeedRatings for a particular test file. I've looked over the file in a binary editor, and the structure of the IFD seems correct. Other software reports the correct value, 138, but ImageMagick reports 1 when I use identify -verbose.
I haven't seen any incorrect values for ISOSpeedRatings for other files. Hopefully, you can download the sample file from https://www.dropbox.com/s/7nqbihosjr3hfw3/P1290018.TIF.
I am running on Mac OS 10.7, and downloaded ImageMagick from MacPorts.
I've looked at the 6.8.6-7 source code, properties.c, and can't spot the problem.