Re: reciprocity failure of paper negs.

I get the message. More is better, but don't forget to go to bed.
  ----- Original Message -----
  From: Guy Glorieux
  To: pinhole-discussion@pinhole.com
  Sent: Thursday, November 29, 2001 6:47 AM
  Subject: Re: [pinhole-discussion] reciprocity failure of paper negs.

    
  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
    
    
    
Received on Thu Nov 29 15:51:44 2001