EI rating for pinhole paper negs?
I thought this would have been already asked, but there's only 3 pages in the paper neg forum and I can't see the answer (although I'm sure I'll see it as soon as I've asked such a simple question and feel like an ass about it).
Anyway, seeing as I've just been gifted a jobo and enlargers, I'm getting ready for paper developing. One thing I've wanted to try for ages is a suitcase-based pinhole camera using paper negs. I've done it in high school many many years ago, and from what I remember it was along the lines of 'poke a pinhole in a shoebox, take a photo, develop, adjust your exposure time if too dark or light'.
But this time I want to use real calibrated-sized pinhole (i've got a lot from Skink to use), I've got a real lightmeter (digisix), I can calculate focal length and f/aperture, all I need to know is what to rate the paper in EI terms to calculate exposure times.
For the record I'm using Ilford Multigrade iv paper, in Multigrade liquid dev for now (maybe when that's out I'll try bromophen too).
An awful lot of electrons were terribly inconvenienced in the making of this post.
f/64 and be there.
witha yellow filter, which will help controlling the contrast in outdoor shots ,I used an EI of 3 for that combination of paper and developer with sucess.
Originally Posted by Dr Croubie
I pre-flash my paper ( search on APUG or F295 for lots of good info about that ) and I too rate MGIV at 3 with a yellow filter, or 12 without a filter. But that is for cameras with lenses. With MGIV the yellow filter can also help control contrast as Ralph mentioned.
For pinhole, I make a series of tests and figure out the bright sun "sunny 16" for each camera separately, for the paper I intend to use in it. It's easy to go from there with a light meter. It does not take long to do this testing... just use little scraps of paper and quickly develop them, adjusting time as you go. I usually find that I'll refine that time slightly as I use the camera. So, for each of my cameras, I only need to remember one number: this one is 20s, another is 45s, another is 1m, and so on.
Also remember that the amount of blue light is what matters most. So late in the day, you might want to add a stop to what your meter says, and similarly you might make adjustments depending on the colors in the scene you are photographing. A couple weeks ago I was at the beach and I forgot to reduce the exposure because there was a huge amount of UV reflecting off the water....
The manufacturer of the paper also makes a series of pinhole cameras. For that series of cameras they have a PDF of an exposure calculator, which can be printed on a normal office printer to help with relating a lightmeter reading to the tiny effective aperture of the pinhole. There is a huge amount of information on the IlfordPhoto site - the datasheet for the paper can also be useful.
In his book "Avancerad mörkrumsteknik" from 1988 (available in english) Lars Kjellberg gives masses of information about various papers, including speeds according ANSI. In it he gives speeds between 250-400 depending of filtration for Ilford Multigrade III.
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Jojje, take care - the units for those speeds may be the ISO paper system these days, or an out of date measurement system of some sort. Harman give a "film"-speed equivalent to ISO3 for MGIV and that seems about right.
Yes, EI3 worked for me when using a yellow taking filterand using Dektol1+2 as a developer. if that still gives you too much contrastuse a higher developer dilution.I've been using Dektol up to 1+8.
Originally Posted by MartinP
hi dr c..
paper photography can be dependant on the time of day and season
the iso can be said to be variable seeing its emulsion only responds a certain band/s of light.
have fun with your project and notice the time of day and weather / conditions
it will help you determine your exposures.
paper, dry plate, wetplate &c all require the photographer be more actively involved, and imho so much more fun
i hope you post your resukts in the paper neg group!
I always forget to look in the groups here at APUG. There's a pinhole group too!
Thanks Martin and Ralph I knew there was a catch - I even double checked Kjellberg's figures! ISO-paper system..?
(I almost always use 120-film with my pinholes.)