Does photo paper have an ISO rating?
I just made a 8x10 pinhole camera out of foamcore last night because I was bored. Since I found out you can contact print with paper, I figured I would buy some 8x10 paper since it's pretty cheap, because I don't know but I figure 8x10 film is expensive.
I found pinhole exposure calculators online at mrpinhole.com but they depend on the ISO of the film you use. But the paper I was going to buy (Illford multigrade IV from amazon.com) doesn't have an ISO rating. It seems like it would make sense that it would.
Anyway, is that a decent paper? I heard that I could buy laser-cut pinholes online, is that true? How important in a pinhole camera is it that the paper be held perfectly flat? Since focus shouldn't be an issue I figure it should be pretty forgiving.
Micro-drill pinholes: http://www.pinholeresource.com/shop/...category_id=16
All photographic paper has a ISO rating: http://www.ilfordphoto.com/Webfiles/...0200232336.pdf
The best way to determine how sensitive the paper is that you are using is through testing.
Paper flatness all depends on what YOU want as a result. In paint can pinhole cameras, the film or paper is curved along the wall of the can. In a traditional pinhole camera, the paper or film is held flat. If you want it wavy, try it out.
That Illford paper data sheet was unclear to me because they seemed to use weird units like P500. I was wondering if it had a simple ISO number that I could use as if it was film. Like ISO 8. There's a bunch of stuff there about filters.
There is a paper ISO rating and a film ISO rating. They are not related.
Ilford MGIV paper has an ISO of about 25. It is not orthochromatic though and has two contrasts at two wavelengths. Graded papers often can be used more effectively than MG papers.
you can get laser cut pinholes from pinholebilly on eBoo,
or through pinholeresource.com ...
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A company in the US makes metal slides with micro holes cut in them at varying diameters. They are rather inexpensive and come packed in neat little boxes for handy use. Tom Miller, an expert pinhole photographer, uses these for his cameras. I'm surprised that he has not chimed in here. He gives workshops at the Photographers Formulary.
can you relate ISO Paper speed to ISO Film speed?
In scientific reports ASA Film speeds are given to photographic papers ranging from 1/100 to 10 ASA Film.
Bettersense: First, welcome to the interesting world of pinhole. You may find it taking more and more of your photographic time. Follow your passions.
As for film flatness, it not only is not an issue, but there are some unique things you can do with pinhole regarding purposely unflat film, such as anamorphic cameras (film wrapped in a cylinder, the pinhole at the end of the cylinder); curved film planes, etc.
There is a slight "defocusing" effect when using a pinhole camera for extremely closeup subjects, an example being when the subject matter is the same distance as the focal length of the camera, in which case the image blur at the film plane caused strictly by geometric effects is double the diameter of the pinhole itself. When I intend on shooting dioramas or other close-in subjects, I use a camera with a purposely smaller-than-"ideal" pinhole diameter.
The quality of the pinhole is at least as important as getting the "ideal" diameter. Actually, there is no "ideal" size from an image aesthetic perspective; it's all good. Smooth, thin-walled pinholes are important, whether hand or commercially made, as they make for smoother tones.
Paper negatives: I've shot paper negatives for the last 15 years, both in glass-lensed and pinhole cameras. The biggest problem I found was high contrast in bright light. The problem with MG paper is that the high-contrast part of the emulsion is activated by the UV/blue light, which predominates in daylight. Therefore, I've chosen to use grade 2 paper; I like RC finish for negatives, as it sits flatter during contact printing, so I use Arista's RC grade 2.
Secondly, I find with pinhole cameras that you can lose shadow details in daylight when trying to keep the highlights from blowing away, so I've taken to preflashing the paper in the darkroom prior to loading in camera. I use a faint, 7.5w type S-11 bulb, suspended about 30" above the work surface in a metal soup can enclosure with a 3mm aperture; typical preflash times for Arista grade 2 are 10 seconds. This yields a faint, gray tone to an otherwise unexposed negative. It helps to bring up shadow details. I actually preflash all my paper negatives, even when used in glass-lensed cameras.
Good luck and have fun.
Bettersense, I agree with most of the above and here is what I would recommend with just about any ilford b&w paper. First of all, preflash the paper. Assume a paper sensitivity of ~ISO 3 and flash it ~3 stops below what you will expose it for your shot. The sensitivity wil be boosted to ~ISO 5-10 or even higher, and you will also get the benefit of a bit less contrast. Next, expose it rated at ~ISO 10 and develop by inspection in slightly diluter-than-normal developer. Maybe two bath dev, just play around.
Oh, and take two or more shots of everything, remember paper is cheap! So make backups so that you can expeirment a bit with development. Also remember that the warmth of your fingertips can be used during development to boost blacks in some selective areas, so you can fight back contrast a bit that way too.
Remember that the paper is mostly blue/edge green sensitive.
Just enjoy and experiment!
Yes, you can relate ISO Paper speed to ISO Film speed.
Originally Posted by AgX
You expose a series of paper negatives until one is properly exposed and one that will scan properly to form a good reversal image. At that point, you have the ISO. Then you compare that ISO (In-camera) to the paper ISO and begin constructing a conversion table.
OTOH, you have to remember that this is not a true emulsion ISO, as the paper picks up speed from back reflections.
An alternative method, which is much harder, is to do exposures on a spectrosensitometer and then integrate the area under the curve.
I have used both methods. I find therefore that Ilford MGIV paper is close to a true ISO of 25, all things considered such as the high average contrast and the back reflection. I have posted some of that here before.