Bill Erickson wrote:
> I'm planning an image of a dark corner in an old building. The > exposure calculates out to about five days with a paper negative. At > what exposure time does one begin to run into reciprocity failure with > paper, and what are the parameters? Bill, I wrote a little piec last year entitled "Reciprocity Nightmare" which may be relevant here and which went as follows (hope it is of help): "I had a dream... It was a dark, lonely night and I was out with my 8x10 PH camera. The New Moon was further darkened by an incredibly rare simultaneous eclipse of the sun and the moon. I could barely see my hands and feet as I walked to the scene I was about to shoot for that winning picture for the First International Nocturne Pinhole Exhibition. Ten times before leaving I had checked that my film holders were fully loaded with film. A single word kept swirling in my mind: r e c i p r o c i t y I must not fail, I must not fail, I kept repeting to myself in the darkness of the darkest forest. Formulas kept poping up in my mind: 10% compound; one-over-the square-root of the inverse of the sunny-16 times three times the speed of my film; add twice the diameter of my pinhole divided by the focal length of my camera to the exposure time estimated for the 3rd f-stop on my right and multiply the cosinus by the coefficient of uncertainty... I knew I could do it. How could I fail with all this simple mathematics so well spelled out on The list. Something tryied to grab me in the dark. I gave it a sharp blow and the thing went blonk. Nothing could stop me from winning the top prize of the Nocturne Pinhole Exhibition at Pinhole Vision. Finally I reached the scene. It was a wonderful landscape I had spotted two days ago after hours of walk in the country side. I set the camera on the tripod. The temperature was a chilling 25 below freezing but I was well covered for a long wait. With my flashlight, I carefully read the spotmeter's reading and worked out the reciprocity factor on my PDA. 258 hours, 64 minutes and 12 seconds... Hmmm... Add a couple hours, just to make sure... It was just that simple! I knew I could do it. But, rats, I suddenly realized that the final deadline for submitting the print was tomorrow with an exposure time of well over 10 days. I forgot to factor that into my equation... -:(( Guy Glorieux
