Supposing your pinhole has a focal lenght of 50mm (the distance between pinhole and film) and your pinhole diameter is 0.3mm, your F-stop is 50/0.3 = 166.6. As high f numbers common on pinhole cameras are not available on the majority of light meters, you set your aperture on your light meter to f/22 and increase the measured time by 58 ! ...> (167/22)**2 ...
Has anyone yet measured the distance from the pinhole assembly's opening (iris?) and the film plane of a Mamiya RB67 film back? That would be great to have documented either here on the forum, or somewhere else in the Zone documentation.
Following up on my own comment, I've measured the distance from the film plane to the pinhole opening in my pinhole assembly. It looks to be ~68mm. So, with that distance, and a pinhole diameter of 0.9mm, that would... if I've got the formula correct ( Distance / diameter = f-stop )... equate my current pinhole to being F/75.6 or.... according to to the calculator provided by mrpinhole, it is F/76 (https://www.mrpinhole.com/calcpinh.php)
I hope this info is helpful to others!
Supposing your pinhole has a focal lenght of 50mm (the distance between pinhole and film) and your pinhole diameter is 0.3mm, your F-stop is 50/0.3 = 166.6. As high f numbers common on pinhole cameras are not available on the majority of light meters, you set your aperture on your light meter to f/22 and increase the measured time by 58 ! ...> (167/22)**2 ...
And take care of reciprocity failure...
Has anyone yet measured the distance from the pinhole assembly's opening (iris?) and the film plane of a Mamiya RB67 film back? That would be great to have documented either here on the forum, or somewhere else in the Zone documentation.
Following up on my own comment, I've measured the distance from the film plane to the pinhole opening in my pinhole assembly. It looks to be ~68mm. So, with that distance, and a pinhole diameter of 0.9mm, that would... if I've got the formula correct ( Distance / diameter = f-stop )... equate my current pinhole to being F/75.6 or.... according to to the calculator provided by mrpinhole, it is F/76 (https://www.mrpinhole.com/calcpinh.php) I hope this info is helpful to others!