I’ve finally had the chance to do some experimenting with my old dslr today.  It’s a Sony A580, which I sent it off to have the inbuilt filters in front of the sensor removed.  So, now it records more of the light spectrum.  Not infrared at the “see heat in the dark” end of things, but definitely more than our eyes can see.  I’ll play with filters to control the light more (it’s a “full spectrum” conversion, meaning it has UV through to IR), but today I just wanted to try it out, and see how well I could focus.   It proved very much a matter of taking a photo, chimping, and changing the settings, what I see through the viewfinder is no longer at all accurate in terms of exposure and what is recorded.  These photos were all at shutter speeds five times or so faster than I would expect to use in this light.  Which makes sense, because there is much more light being let in.  Someone, somewhere probably has some kind of fancy calculation rules for working this out, but for now I’ll just spin dials until it looks right.