pinhole exposure times

Hey all

I wanted to shoot some images with the pinhole option of my Diana camera. I was

wondering if anyone knows what the aperture of the pinhole on the Diana camera

is, in order to calculate the exposure time. In one, but only one place, on the

internet I saw that it is f/ 150.

anyone have another opinion?

 

THANKS

May be even less. What film you are going to use? Many common films today are very forgiving then exposure gets longer then 5-10 seconds. That is to say exp. of 20 sec or 40 sec. or 60sec will ptoduce comparably similar result. I would try 1 shot for 30 sec. 1 for a minute and 1 for 3 - 5 minutes .

Sorry, I don't know the aperture for the Diana, however I do a fair amount of pinhole work

with a Zero Image camera. It's aperture is f/138 and I'd imagine the apertures would be

similar. I shoot Ilford FP-4 at EI 64. My exposures in sunlight are 1 sec. In open shade

about 12 sec. Beyond that I use a light meter and a reciprocity table to establish my

exposures.

You can calculate it just like the aperture of a lens. Divide the diameter of the pinhole into the distance from the pinhole to the film and that gives you the effective aperture. In the case of my own pinhole camera, the pinhole is 0.5 mm and the distance from the pinhole to the film is about 85mm giving an aperture of about f/170. Using a lightmeter , you can work back to an exposure time.

Go into a sewing supply store with your Diana and try different needles to see which is the largest that fits into the aperture. Notate the number of that needle. Then look at this chart for diameters of needle numbers:

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4 - .036<BR>

5 - .031<BR>

6 - .029<BR>

7 - .026<BR>

8 - .023<BR>

9 - .020<BR>

10 - .018<BR>

12 - .016<BR>

13 - .013<BR>

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All diameters are in inches.

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Then measure the distance between the aperture plane and the film plane in inches. This is your focal length.

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Divide the focal length by the diameter and you have your f stop.

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For instance, assuming your needle is a number 10, and your focal length is 3 inches: 3/0.018 = 166 2/3. Use f/160 in your calculations. It is 1/3 stop below f/180, which is two stops above f/90, which is two stops above f/45, which should be on your light meter. So, f/160 is three 2/3 stops above f/45.

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Assuming bright conditions and a 125-speed film, at f/16 your shutter speed should be '125. That means f/22 at '60, f/32 at '30, f/45 at '15, f/64 at '8, f/90 at '4, f/128 at '2, and f/180 at 1 sec. That means f/160 at just shy of 1 second.

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I would just call it f/180 if I was using neg film. It will make calculations more quick, and 1/3 stop of overexposure won't hurt your negs.

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You are better off using longer exposures with pinholes, in order to minimize camera shake from opening and closing the shutter. Use ND filters or slower films to get those speeds. You can rate Pan F at 25 easily...in fact, I find that I have to anyhow in order to get detail in the shadows.

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Be sure to look at the reciprocity chart for your film.

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keith

Just asked my friend who owns one of the new Dianas. The focal length of the lens is 75mm. I still don't know exactly what size the hole is, however.

 

keith

hi dora,

 

as many have suggested here, the reciprocity departure of your film has a much greater impact on the exposure than the exact f-stop and will make it very difficult to over expose your images with pinhole photography, within moderation. sometimes i use a red or 2x ND filter for even longer exposures and my experiments have shown that with some (traditional grain) films such as neopan and fp4, the difference between 1 minute and 4 minutes in flat sunlight has very little effect on stationary highlights. remember also, you can always add or subtract a little development to control your highlights.

 

rj

Dora,

 

A lot of good comments here. Importantly, as Robert points out, with pinhole times it is hard to overexpose, and there is a lot of leeway in exposure with these times.

 

I have a Holga pinhole, about 50mm, with a pinhole of f/192. It's about the optimal size for that focal length. With a focal length of 75mm, f/192, f/200, f/180 as suggested by Robert, f/225 - any would be ok.

 

Nice thing about f/180 for cameras with these sorts of focal lengths and presumably proximate f/stops: Most meters go to f/90, and you just multiply time by four (before applying reciprocity). I just do that with my Holga. So I'm actually using f/180. No meaningful difference between that and f/192.