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04/20/2006 02:47:38 PM · #1 |
What is the difference between Hoya's R72 & RM90 and why a near $200 price tag difference? And which is better for using on a Canon DSLR?
(Yes, I the following "R72 passes only infrared rays above 720nm; RM90 passes only that above 900nm." but what does that mean in the real world?)
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04/20/2006 03:13:11 PM · #2 |
The 720nm cutoff of the R72 is much closer to the visible red spectrum, in fact it does pass some deep reds. The 900nm cutoff of the RM90 is much farther into the IR spectrum.
Canon DSLRs already incorporate a "hot mirror" that reflects the bulk of infrared, so using the RM90 would result in VERY long exposures. The R72 will at least give more manageable exposure times, though hand-held shots are not going to be possible. The R72 is the right choice for Canon DSLRs (with the exception of the 20Da and modified units of course.
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04/20/2006 04:26:17 PM · #3 |
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04/20/2006 04:34:43 PM · #4 |
| Can you do IR with the 300D? |
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04/20/2006 04:41:45 PM · #5 |
Originally posted by DrAchoo:
Can you do IR with the 300D? |
Yes. As with other Canon DSLRs, exposures are long (several seconds and up even in bright daylight), and you need a filter with a shorter wavelength cutoff (like the R72).
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04/20/2006 06:12:22 PM · #6 |
Originally posted by kirbic:
Originally posted by DrAchoo:
Can you do IR with the 300D? |
Yes. As with other Canon DSLRs, exposures are long (several seconds and up even in bright daylight), and you need a filter with a shorter wavelength cutoff (like the R72). |
There's another way to do IR while getting around the problems of sensors with IR-blocking coatings. Some cameras replace the sensor with a single-use strip of some type of plastic loaded with light-sensitive chemicals, and you can choose strips that are sensitive to IR light. :)
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