Getting info from Canon Europe is not something I find easy. Do Canon L lenses tramsmit infrared? I have a body that I have replaced and am wondering about getting the sensor modified to respond to infrared, but that is a waste of money if the lenses won't let these wavelengths through. I met someone last year who had done it and I think his kit is Nikon.
Thanks - Jonathan Cross
Canon's L-lenses are a mixed bag regarding infrared transmission. As others have noted, the problem lenses generate a very obvious hot spot near the center of the frame due to internal IR reflections. This can be corrected to some extent in Photoshop, but it kills the image contrast that is one of the most appealing things about IR.
My personal experience with an IR converted Eos-1Ds:
The 24-70 f:2.8 is wonderful, no problem at all. If anything in infrared its sharpness is greatly enhanced compared to visible light. I just printed an image at 24x36" from a single frame capture, and the detail in vegetation is astonishing.
The 24-105 f:4 is almost as good.
The 70-200 f:2.8 is unfortunately almost useless; there's a very obvious hot spot near the center of the frame in any sunlit scene, which includes 99% of appealing IR subjects.
The 100-400 zoom is not bad; no hot spot, and the apparent increase in sharpness overcomes much of this lens's corner softness.
The original 16-35 f:2.8 zoom can work, but there'll be an annoying small flare or hot spot if the sun is just outside the frame. It's worth trying to hide the sun behind something to avoid this. (I haven't tried the 16-35 f:2.8 II yet; I'm waiting for a sunny day and a bit of spare time.)