On Thu, Jul 3, 2008 at 9:21 AM, Anthony Farr <[EMAIL PROTECTED]> wrote: > 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.
I knew some one out there would answer me.:-) > It must be liberating to have an IR capable camera that isn't bound to a > tripod. It is. Dave > > 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 > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. > -- Equine Photography www.caughtinmotion.com http://brooksinthecountry.blogspot.com/ Ontario Canada -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
