IR

[compilerbitch]

I just got an IR filter (square, Cokin P-series, 89B). To the naked eye,
it looks completely black -- if you look through it, you can /just/ see
bright objects as a dim red image. I wasn't stupid enough to look at the
sun through it, of course (it's pretty much transparent at IR frequencies).

Anyway, putting it in the filter slot in the compendium shade on the
Cambo worked a treat. I focussed the image with no filter in place on
the ground glass, locked everything down, then inserted the BetterLight,
stopped down to somewhere between f16 and f22 and put the filter in
place. Doing a prescan, I found I'd way underestimated the sensitivity
at IR, so I ended up upping the line time to about 1/250th and dropping
the ASA rating to the minimum (just under 400). The focus looked OK, so
I made an exposure and checked it in Photoshop. It wasn't bad, but the
focus was slightly off -- this is not too unexpected for IR. I then used
the BetterLight's focus meter to get it dead on -- the next scan was
fine. This is a crop from that scan, actually a fairly small area in the
top right of the original.



The shot was taken in reasonably bright sunlight, about an hour before
sunset. I took the image data from the red sensor only, but
(interestingly) I found that all three sensors (R, G and B) seemed to be
about equally sensitive to IR.

Comments

[compilerbitch.livejournal.com]

Yes, I am planning to come to Bab5 this week. I wanted to go last week, actually, but I was feeling really dead tired and wanted to get some rest before my epic trip at the weekend (SFO to London Heathrow, arriving about 8am, pick up hire car, drive to Leytonstone in East London for breakfast and to pick up doseybat, then to Cambridge for lunch in College and my graduation in the afternoon (I'll post more about this later in a locked post), then to a hotel for the night. On Sunday, drove to Gatwick, got on a plane at 1pm to Dallas, Texas (10 hour flight), 2 hour wait at the airport, then a 3 hour flight to SFO. I got home at 1.30am Monday morning. Something like 13000 miles in 3 days).

I will friend cuthalion forthwith. :-)