Now, to continue the discussion, I would like to know how the photographers get away with the long exposures usually required for pinhole photography when the backs have a limit for exposures of one or two minutes?
Chris Ireland uses a Phase One back and mentions exposure times of 1 second up to 9 mins (at f180!).
How can he do that? Wouldn't the sensor have gone into meltdown before it got to 9mins?
Phase One IQ180 and Mamiya Leaf Credo are each spec'd for 2 minute max exposures.
Phase One P20+, P21+, P25+, P30+, P45+ are each spec'd for max one hour exposures. Of these the P45+ is generally acknowledged as the king of long exposure amongst all backs, especially at times over 30 minutes.
So 9 minutes is not even breaking a sweat for a P45+.
Given that there is not that much scene detail (cause it's a pinhole, not an uber sharp modern lens) you can safely apply fairly aggressive single-pixel noise reduction and exceed the stated specs by a bit.
My pinhole was a larger-than-normal pinhole and I hand held it at something like ISO800. Probably some camera shake, but I mean, it's a pinhole - I wasn't exactly obsessed with sharpness :-).
These times are:
- at lowest ISO
- at ambient temperatures around 68F (20C). Longer is possible at lower temperatures, less at higher temps.