DIY pinhole lens' aperture is ƒ00, which can't be changed and pictures turn out mostly black

Question

I just made a pinhole lens for my Canon EOS 1000D (Rebel XS), but now I have no idea what to do next. The bulb-mode is on and ISO is 400. Camera says the aperture is ƒ00, which I can't change. What does it mean? Is there no diaphragm?

Does the camera even recognize my lens? If it doesn't, is there a setting to tell the camera there is a lens even if it isn't recognized?

Also, if I take a picture, there is a lot of black and barely a little point can be seen. Not only trough the viewfinder, but also on the picture at the screen.

I constructed the lens by making a hole in the middle of a bodycap with a drill. Behind the gap I put a piece of aluminium, and I made a small point in that with a needle.

Can anyone help me? I really really want this to work, because I'm a huge fan of pinhole photography.

Answer 1

DSLRs read the aperture data from the lens via electronic connections. Reading ƒ/00 basically means that either there is no aperture data on the lens' chip or that there is no electronic connection at all, which is probably the case with your DIY pinhole lens.

The diaphragm resides always in the lens, not in the DSLR. So: there is no diaphragm if you haven't built one — and it would be rather useless in a pinhole lens.

There is no setting to tell the camera that there really is a lens even if the camera doesn't recognize it. This is more a problem for the autofocus system, your DSLR should be able to take a picture even without a lens.

The reason your photographs come out almost black might be because your exposure time is not sufficient. To determine a "correct" exposure, you should either calculate the aperture of your pinhole lens or go and experiment, which is usually easier or at least a lot more pleasant option than to worry about the math.

Anyway, Wikipedia gives a concrete example on calculating the aperture of a pinhole lens:

The f-number of the camera may be calculated by dividing the distance from the pinhole to the imaging plane (the focal length) by the diameter of the pinhole. For example, a camera with a 0.02 inch (0.5 mm) diameter pinhole, and a 2 inch (50 mm) focal length would have an f-number of 2/0.02 (50/0.5), or 100 (f/100 in conventional notation).

If your pinhole's aperture is ƒ/100, note that it is approx. 5⅓ stops* smaller than a ƒ/16 lens, and therefore needs approx. 39 times** longer exposure, if other settings are intact. The Bulb setting you are using doesn't have a fixed exposure time — with bulb, the camera exposes as long as you hold the shutter.

Viewfinder can't be much helped, though. You could get a rough estimate of where you are pointing your camera at by first using a regular lens and when done switch the pinhole.

_{*) See: http://imaginatorium.org/stuff/stops.htm
**) (100 ÷ 16)² = 39,0625}

Answer 2

A pinhole is essentially a very small and fixed aperture, so you will need to use Manual mode and set a nice and long exposure (A second or five should be good to see what kind of exposure you're getting for starters) to determine just what you're getting out of it.

Also, you will need a lot of light to get any picture at all on your viewfinder since there is so little light passing through the pinhole. Depending on the hole you've made and the exact placement and distance, it could be the equivalent of f/64 or more, so think accordingly.

Answer 3

The camera cannot read the lens aperture, that is why it says F00.

That is good for you because you have a pinhole lens which, well, does not have an aperture by definition. (Note that sometimes a camera reports this when using legacy lenses too simply because it cannot determine the aperture).

Canon makes no pinhole lens, so there is little chance the camera will recognize it.

What you need to do next is either stay in bulb mode or go to manual exposure if you want the camera to time things. The point is that there is only ISO and shutter-speed to control at now.

If your photos are coming out dark then either take a longer exposure or raise the ISO or both. You'll have to experiment. Try 30s, 60s, 2mins.... until you get a bright enough image. In bulb mode that means hold the shutter open and let go after the set time has passed looking a watch. Raising the ISO will let you get away with a shorter exposure.

Answer 4

While a mechanical lens can't communicate its value electronically to the camera, a pinhole lens does have an f-stop value. The pinhole itself is literally the aperture of the "lens", and the focal length is the distance from the pinhole to the focal plane. And the f/number is simply the focal length divided by the aperture.

You can find this focal length value by looking for the ⌀ symbol on your camera body, which represents the location of the sensor (see What does the theta symbol near the flash represent?). Measure from there to the location of your pinhole. (Technically, since there's no lens, this isn't really a "focal length", but it functions in the same way.)

Measuring the size of the pinhole itself is somewhat more difficult to do with meaningful precision, but one suggestion would be to put the material you've put the hole in on a scanner, scan at a certain DPI, and then check how many pixels across it is. (I'm not sure I'd use that method in a scientific paper, but it should be good enough to get a reasonable idea.)

Then, simply divide the first number by the second, and there you go. For what it's worth, Lensbaby says the f-number of their Pinhole Optic is f/177. That sounds ginormous, but is only 7 stops down from f/16, the same as from f/16 to f/1.4.

This will help you calculate the exposure value you need, and therefore the shutter speed. But it also may end up being imprecise enough that trial and error is the better method than all the math in any case. After all, there's very little cost to trying with a digital camera.