Help with a pinhole camera and Fuji crystal archive paper

[narcosynthesis]

I am debating trying my hand at the art of pinhole photography, and was looking for some advice and opinions from those who know somewhat more than I do on the subject of the papers and setup needed...

Through work I have access to small amounts of Fuji crystal archive paper (around 4x10" sized sheets) and the means to develop them, so my thought is to experiment with them as the 'negative' in a pinhole camera.
I know the basic idea of pinhole photography, but it is the details that escape me in how exactly to get it setup. The idea would be to use something like a chocolate tin (Cadburys roses/Quality street - about 10" diameter) with the paper around the inside edge of the tin and a pinhole made on the opposite, the shutter being something like black tape that can be removed and replaced to 'seal' the pinhole.

The problem I have is that I have no idea how to calculate the exposure. Being that the pinhole will be made by me, I have no idea how to accurately calculate the aperture value of such a small opening, and also no real information on the paper and how sensitive it will be.

Is there anyone that can help put me on the right track? If I get a vague idea I can at least try a test print and adjust, but some starting value would be nice...

Any help would be most appreciated.

[Andrew]

you'd better get in quick because Worldwide Pinhole Photography Day is THIS WEEKEND, April 24th
http://www.pinholeday.org/

well a camera is just a light tight box, isn't it ! And, in general you'd paint the inside black to reduce unwanted reflections... and it's easier to manage if you make a box with some sort of a tripod mount so you don't get those silly images that are half full of foreground gravel and grass because the camera's sitting on the ground. Otherwise, look for a bench or rock to put your box on to get the camera off the ground.

If you already have a functional camera you can always use the existng camera to save time because all you have to do is put a pinhole into a body cap or on a lens board... Unless you want to bends and distortions of a curved film plane in which case you will need to make your own. Using an existing camera will save you a lot of time if you want to get going by tomorrow!

paper generally has an iso rating about 3 which means really long exposures so you might consider using film instead and even then you'll have to allow for reciprocity failure.

you can get an idea of your pinhole aperture by scanning it at highest res and counting pixels in the resulting image. There are obviously other ways of measuring or you can buy ready made pinholes if you want to get fancy.

Make an estimate of pinhole to film plane distance and F = distance / pinhole diameter

That should let you guesstimate an exposure but there's no substitute for a little bit of trial and error to get it right because you may have an error in measurements or you may not know exactly how your film/ paper will react to the long exposures at small apertures

there is an optimal diameter of pinhole for any given distance to film plane and there are some calculators available on the net if you google search but generally you aim for an f-value of about 150 to 300. Much bigger or smaller and the image quality goes off. My own feeling is that a nice smooth hole in a thin material is important too.
Have a look here: http://www.mrpinhole.com/calcpinh.php

You can buy thin brass shim at a hobby shop which is nice to work with but you can also use aluminium from a drink can. You'll need some fine abrasive paper because the nicest technique to get a small hole is to put your pin part way thru the sheet of metal so it raises a bump on the far side and then sanding away the bump. You can have several repetitions of the sequence to get a nice small hole but if you stab a pin all the way thru in one go the edges will be rough and you may tear a very fine shim.... it's much more reliable to wear down a thicker sheet of metal. And once you finish you can wash the pinhole with water and detergent to get as much rubbish out of the hole as possible.

there's a lot of information in the archives at the pinhole forum:
www.f295.org/Pinholeforum/forum/Blah.pl

[SMBooth]

This should get you going.

http://www.pinholephotography.com.au...t/project.html

[narcosynthesis]

Due to the practicalities of procuring and developing the images, I am 'stuck' with the Fuji paper if I want to follow through with the idea - while film may be more practical, it comes with the need to source film, chemicals, developing kit and so on, so impractical but cheap it is...
Similarly with the camera, I do have various 35mm SLR's that could be used with pinhole 'lenses', but based on the idea of a 4x10" negative I am really looking to (very small) budget DIY - basically a converted tin.

Checking out the pinhole calculator (with rough numbers):
10" focal length
0.05" aperture at f200 (larger than I was expecting, and somewhat easier to make with some degree of accuracy)
exposure time of 52 seconds with an ISO of 3 and a sunny day

The site does mention typical photographic paper used being around ISO10 - I am assuming this will be for typical darkroom B&W paper, to which I have no real idea how the Fuji Crystal archive compares - I am used to it being run through a digital minilab that exposes images automatically via RGB laser. At ISO 10 I get an exposure of 15 seconds, with some wiggle room in exposure value I believe I should get something, even if not really perfect quality.

I think some reading at f295.org may be in order before starting work too, I may miss worldwide pinhole photography day by a wee bit, but I can at least take it as inspiration

Cheers for the help.

[Andrew]

I'm curious, how are you getting you paper negs processed?

[SMBooth]

Ive heard of people using cibachrome in pinhole so a search on that and pinhole might point you in a direction. Hopefully you will post you results here when you have given it o go. I don't know anything about the paper you have, as I have only used B&W papers.

[narcosynthesis]

I'm curious, how are you getting you paper negs processed?

I have access to a Fuji minilab that prints to the crystal archive paper, so should be able to use the printer there (bypassing the exposure section, and just utilising the dev tanks).

Not something I can do on any real scale, but I can hopefully run a few images through, if only for the curiosity of seeing how it comes out.

[Tom J McDonald]

Do you have a method of turning the negatives into positives? Or just going to scan them?

[narcosynthesis]

Do you have a method of turning the negatives into positives? Or just going to scan them?

It is being shot straight to the Fuji paper, so I will have a print rather than negative.

Whether the print will be negative or positive I have absolutely no idea, as I know next to nothing about the paper other than 'it is used in the machines I have at work', only one way to find out though...
I guess if they are positive, then I have a print. If they come out negative, then probably scanning them and inverting them will be the plan.

[Tom J McDonald]

As far as I can tell, they will be a negative.