Quote Originally Posted by Chan Tran View Post
I wouldn't use the exposure factor at all since the aperture is known (i.e. f/333) the film speed or rather paper speed is known as ISO 3.2. What else does one need except for the reciprocity characteristic of the paper?
I doubt many meters can give a direct reading for f/333 or f/256. My Digisix stops at f/32 and my Sekonic L-508 ends at f/128. Pinhole Designer can actually output a table (Excel spreadsheet compatible) with a list of settings compensated for the exposure factor and optionally, reciprocity. The latter is only for some films and a bit suspect in at least one case I've tried.

One notes the shutter speed indication for f/22, uses that to index the table and get a value of how long to hold the button down. Such a table easily fits on a small card. Obviously one can mentally diddle the f/22 and shutter speed values by stops and come up with a new shutter speed, but the chart is simpler (based on my one day a year experience!)