Infrared Filter

[mdaddyrabbit]

I want to try a infrared filter on my 20D, I am not sure what to get, I dont know anything about R72 or B93 I just like some of the effects I have seen. What to buy where to buy it, I looked at B&H, Are all IR filters this high? Please help me with what I need and a good place to buy.

[Longwatcher]

Don't know about 20D for sure, but most people, including myself, have had good luck shooting near-IR photos with Hoya R72 filters.

You are looking for a filter with a cutoff of around 720nm which is what the 72 in R72 means. In the case of the Hoya it has a fairly sharp cutoff, but still lets in a small amount of visible light mainly in the red portion of the spectrum.

From my research you don't want a IR filter with a cutoff over 850nm for any current consumer digital SLR (as opposed to industrial/military). And most of the Canon's seem to need around 750nm cutoff or lower.

A cutoff is the point at which the filter cuts off more then 50% of the light in that portion of spectrum and below. A good filter will show in a chart as having a very steep line at that point in the graph depiction of amount of light versus region it lets through.

Hope that helps you a little bit in finding a filter.
If confused get a Hoya R72, it is the most likely to work and still get you IR shots.

[mdaddyrabbit]

WHere might I get the best price for a R72?