Paper for Pinhole cameras - how much exposure?

wallacjm

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I work in a public school. In April I am my 1st and 2nd graders will be taking pictures with them. I am using paper that was given to me without the original box.
Before I let my students use the cameras, I need to figure out what ISO the paper is. I believe it may be Kodak or Ilford. I know it is RC paper.

Could someone recommend tests that I could do to figure out the correct ISO for this paper?
 

NedL

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My advice: don't even worry about ISO... base everything on "sunny 16". If I knew how big your cameras will be we could narrow this down a bit... but cut up a piece of paper. On a full sunny day, make exposures: 15s, 30s, 45s, 1m, 2m. Develop and choose the best. Then on the day you use them, just double that exposure for each stop below EV15@ISO100. If it is late afternoon or early-ish morning, add 1/2 stop for less blue light...
 

MattKing

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I've tweaked your title, to encourage those who have already done some experimentation to chime in.
It is probably helpful to understand that photographic paper is a lot less sensitive to light than most films. For that reason, paper isn't assigned the same sort of "ISO" rating as film is.
@NedL 's suggestion is a good one.
The size of your camera - focal length - and size of pinhole/effective f/stop will help us help you.
Just a reminder: if you are going to make several separate and different test exposures, you will need to mark somehow the individual sheets in order to tell which is which. Clipping different numbers of corners is one way.
 

koraks

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wallacjm said:
I am using paper that was given to me without the original box.
Click to expand...

Have you verified the paper is still OK to use? Kodak hasn't made any RC paper for ages. Any that's still around may be fogged beyond usability, even for experimental uses.
A box of fresh paper doesn't cost an arm & a leg if you buy something like Arista EDU in a small size.

Arista EDU Ultra VC RC Glossy 5x7/250 Sheets

Arista EDU Ultra VC RC Glossy 5x7/250 Sheets - The Arista.Edu Ultra Line of Film and Paper is the educator’s choice for their students.Arista.EDU Ultra VC RC Paper is a high quality, economical, medium-weight resin-coated enlarging paper for traditional black and white printing.…
www.freestylephoto.com
 

mtnbkr

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IIRC, when I was shooting paper negatives in my Crown Graphic, I rated them somewhere in the 1-3 ISO. Exposures seem to be in the ballpark.
 

Kevin Allan

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I shoot Ilford MG V RC at ISO 6. If you preflash the negatives, then ISO 8 is achievable, but testing would be necessary to eastablish the appropriate pre-flash time with your light source.
 

DWThomas

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About a dozen years ago I did some pinhole shots using Arista.EDU #2 RC Paper with a slight pre-flashing and found readings at EI 6 worked fairly well. That produced exposures between one and two minutes at f/275 on a very slightly hazy sunny day; an early adventure with my home built 8x10 camera. (I've mostly used Fuji HR-T X-ray film since.)
 

336v

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I use Ilford RC B/W paper as negative in the camera, and setting exposure assuming ISO=3 gives me good results.
 

Kino

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If this is of any help...

Paper negative on Ilford MGRC DeLuxe Glossy rated at 3 ISO, 8x10 sheet in 8x10 camera.

Really, you just have to do some tests...

 

RalphLambrecht

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Kino said:
If this is of any help...

Paper negative on Ilford MGRC DeLuxe Glossy rated at 3 ISO, 8x10 sheet in 8x10 camera.

Really, you just have to do some tests...

Click to expand...

Photographic enlarging paper is around ISO 3, but be careful, as it's very sensitive to blue, resulting in very high contrast. For pinhole use, I'd recommend a yellow filter, which reduces the ISO even further
 

koraks

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RalphLambrecht said:
it's very sensitive to blue, resulting in very high contrast
Click to expand...

These are different things, though.
It's mostly blue-sensitive, that's one thing. Which makes sense if you look at how multigrade/variable contrast paper works.
It's high contrast - which is a different matter.
It's theoretically (and practically) possible to make a low-contrast, blue-sensitive material. It just so happens there's no use case for it, so nobody bothers to put it on the market.
 

mzjo

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FWIW The out of date Ilfospeed that I use in 9x12 film holders seems to be about 3ISO. The Fomaspeed that I use in the same camera in 5x4 film holders is about 10-12ISO. Can't beat testing, it"s what gave me an image (in a diy half-plate box) for the last WWPPD. I now have a new box, using 5x4 and 9x12 paper negs for the 2026 edition.
 

xkaes

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I agree with what's been said. A good starting point is ISO 3, but you should test the paper first to see if it is fogged -- as also mentioned. No exposure needed. Just develop a piece for five minutes and fix it. Compare that to a piece that is only fixed. See a significant difference???
 
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