David J Brooks wondered: "I am suprized at the difference you get in shooting speeds by moving the filter from the front of the lens to infront of the sensor.
I cannot see way it makes that much difference as it is blocking light, one way or another, but it does." Dave, The extra sensitivity happens because not only has the R-72 filter been moved to behind the lens, but the IR cutoff filter has been removed altogether from over the sensor. In a conventional setup the only light getting through to form an image comes from the very small gap in wavelengths between the visible light that the R-72 blocks, and the IR light that the IR cutoff filter blocks. Converted cameras get as much IR image as their sensors can use. I also suspect that the "R-72" filter in these cameras isn't exactly an R-72 but lets through more visible light. That would be why blue skies aren't nearly black, and why colour photos look more natural, with that extra dimension coming from the IRs effect on foliage. It must be liberating to have an IR capable camera that isn't bound to a tripod. It's a handy thing that unfiltered sensors have extended sensitivity to IR, which is artistically interesting. Film has extended sensitivity to UV, which is mostly a PITA. Regards, Anthony Farr -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
