I'm planning to get a Sony NEX-7 converted to do infrared (IR) photography by lifepixel, who did the conversion on my Nikon DSLR several years ago. Now they have, in addition to the previous full-time-IR conversions, a "full spectrum conversion", in which they remove all filtering in front of the sensor and one can take either visible, IR, or UV by putting appropriate filters on the front of the lens.
It sounds like a real convenience to have to carry just a couple of extra filters instead of an entire extra body for IR (in addition to one for regular visible-light photography). However, I'm concerned there may be disadvantages I'm unaware of. The one I can think of offhand is that one would have an extra filter (possibly two) that would degrade the image to some extent. B&H carries the filters I would need, but they aren't listed as multi-coated. Does someone here have any objective feel for how much the image would be degraded? I'm not worried about pixel-peeping levels, but only a level of degradation that would be noticeable in 12"x18" prints. (I'm using the Sony 18-200mm lens for convenience, so I'm already not getting the very best sharpness out of the Sony images, and that's OK.)
If I'm stacking two filters on the 18-200mm lens (one to get the wavelengths I want, plus one polarizer), is it likely to experience undesirable levels of vignetting? Or is a polarizer inappropriate for IR photography anyway?
Might there be any other disadvantages to the full-spectrum conversion (compared with the IR-only conversion)?
Thank you,
Lisa
