pinholes and film speed

I have been testing with HP5+ film to see what film speed to shoot it at.
To my surprise, it seems as if its speed in my pinhole camera is about 1000!
It's rated at 400. The way I figure exposures is based on the fact that my
pinhole is f352. That's supposed to be 30 times whatever f64 is. So I
multiply the f64 time by 30 and then adjust for reciprocity failure, using a
formula I found online from Ilford: raise the metered time to the 1.48
power. This accords with most reciprocity failure charts that I've seen.

But to get my shadows thin enough, I have to shoot this at 1000. I have had
a lot of old cameras with old shutters that required different speeds than
the regular one because, I assume, the shutter is a bit slow. But a pinhole
doesn't have a shutter really! So, I wonder why you end up having to shoot
as if the film is much faster than it is? Has anybody else noticed this?

--shannon
Received on Wed Jul 3 17:39:52 2002