This week I received my "$299-deal" EOS-M converted to standard 720nm IR by Life Pixel and have started taking shots. I did some systematic tests today for hotspots on the lenses I would typically use.
I am sharing the results with the community in case this is useful for others -- I used a lot of the current shorter L primes, modern zooms, a couple of EF-Ss and the two original EF-Ms. http://sdrv.ms/16B8HGmSummary results:
- 18-55M starts to show noticeable hotspot from ~f/11 upwards at 18mm, less pronounced at higher zooms.
- 22M starts ~f/16 upwards, not strong.
- 17-55S starts faintly at ~f/16.
- 35L and 100L ditto.
- 135L starts faintly at ~f/22.
- 70-200IIL and 24-70IIL starts ~f/16 to varying degrees at all zooms (24-70 ok at higher zooms).
- 16-35IIL starts faintly ~f/16 and gets pretty bad, and starts ~f/8 at 25mm and 35mm.
- 10-22S, 24-105L and most primes very clean.
Looking at the thumbnails exaggerates the effect and is handy to spot trends. Even the worst performer is very usable at wider apertures. Whether any are noticeable in practice will depend on the subject and conditions!
There are a number of lens IR performance lists on the web, but I don't know of one for the EOS-M specifically, nor for the EOS-M lenses. Hope this helps!