Originally posted by RioRico Some cheap IR-pass filters may have hot-spots with uneven light transmission
And certain lenses are know to contribute to this effect - the DA15 has a hot spot with the R72 it isn't as bright as the hotspots caused by other lenses - but it
is there.
Originally posted by Just1MoreDave Digitalis saved a bit by using a lens that takes a 49mm filter.
Indeed I did, however I currently have a Lee R730 square filter on order to be used with other lenses and camera systems
Originally posted by RioRico I forgot to mention that fast lenses aren't necessarily your friends when shooting IR. Remember that you're already losing a lot of resolution, since EMF is only hitting the R pixels, not the G and B. The Bayer filter is RGBG so you've lost 75% of the pixels -- that 12mpx camera now outputs an image with 3mpx real resolution. That means that the image looks a bit fuzzy.
Ever heard of forbidden transmissions? the G and B pixels are still receiving light - because the molecular structure of the organic dyes used in the CFA in our cameras are much smaller than the wavelength of IR. Infared wavelengths can pass right through/around them
Honl Flash filters photographed under visible light:
the same flash filters as seen through a Hoya R72 IR filter:
just a word of warning with IR photography - lenses like the DA 15mm f/4 ED AL have superb handling of flare under visible light - but this is the kind of flare you get with the Hoya R72 on the DA 15mm f/4: