Checking out autofocus in the Near IR using a modded 20D with clear glass over the sensor and a Wratten 89B (IR-Pass) used as a pop-in Front Filter. Images on the left show the full frame of the 20D, on the right 100% 1:1 central crops (if you have clicked on "original" size below). In all cases only the central focus spot was used. In practice, for daylight landscape photography it's more practical to activate all the focus spots, especially since you cannot see where the center spot is pointing through the blackened viewfinder. Newer DSLR models like the 450D, 40D and 50D have Live-View that is a great boon for both framing and focusing IR. Though one-click autofocus may sometimes be still required for fast moving subjects, sports, birds in flight and similar. Even though the 28mm and 50mm lenses can be opened wider, in actual use I would prefer to close them down even further to f4 or f5.6 to sharpen up things. These lenses have to be closed down that far even for visible-light astrophotography. As seen also for visible light astrophotography, the Canon lenses >=100mm in focal length seem usable wide open, or close to it. Note that the above crops are not only a test of the autofocus, but also of the capability of the lenses to perform in IR when wide open, or nearly so, e.g. other images available at http://www.pbase.com/samirkharusi/infra_red demonstrate the excellent IR images possible from the 14mm and 28mm when closed down.

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