Pinholes are an alternative to lenses, Pinholes don't let as much light through as a lens, but they do give enormous depth of field. You can buy pinhole plates but I have made my own with small drills and stainless steel (or brass) shim material available from engineers merchants or model shops.
I've found that holes in the region 0.4mm to 0.8mm diameter are suitable for large format photography. I've tried these on an APS-sensor digital SLR too but the smallest drill size I have, 0.4mm, was too fuzzy for my taste. Smaller formats need smaller holes, and I found that I got better results from a piece of black masking tape pricked with a needle! On 35mm cameras I use a drilled body cap on extension rings to give me "zoom" control, but don't expect to get wide angle with an SLR because the mirror prevents the use of short focal lengths.
|Home made pinhole plate taped to a lens plate for use on a large format camera. I use the central 0.8mm hole for composing then switch to one of the smaller holes for exposure. Black self-adhesive tape is stuck over the unwanted holes.||Rear view of pinhole plate. Note that it has been painted matt black to reduce internal reflections. The distance between the holes is minimal and doesn't affect framing since I tend to be generous with the edges!||Closup of the pinhole arrangement.|
A pinhole is capable of giving a range of apertures: the greater the distance between the pinhole and the film, the greater the aperture and hence the greater the depth-of-field. Aperture from f200 to over f1000 are normal in pinhole photography. The trade-off is that you need long exposure times, so a tripod is a almost a necessity for pinhole photography.
Pinhole focal length
The distance from pinhole to the film is called the focal length. As this distance is increased, the field-of-view on the film narrows. On a view camera this means that the focus control that racks the front standard becomes a zoom control.
Pinhole exposure times
How do we know what the exposure should be? We can use a light meter, but not directly as most meters are not marked for the sort of apertures we use in pinhole photography. There are equations that relate pinhole diameter and focal length to aperture and light meter setting. There is also an equation that gives the optimum focal length for a pinhole (though this is based on diffraction theory rather than aesthetics). The equations are shown here, but I find the tables of more practical use in the field - I keep these tables in my A6 looseleaf field notebook for reference.
fpin = aperture of pinhole
fmeter = aperture set on light meter
Dpin = diameter of pinhole
d = distance from pinhole to film, that is, the focal length
doptimum = the smallest distance from pinhole to film to minimise diffraction effects
Tpin = actual exposure time for pinhole (not including any reciprocity adjustment)
Tmeter = exposure time indicated on meter
Formula 1: doptimum = (25 * Dpin) ^2
Formula 2: fpin = Dpin / d
Formula 3: Tpin = Tmeter (fpin ^2 / fmeter ^2)
Formula 1 gives the optimum focal length for best definition and shortest exposure times, but this may not be your objective, so feel free to ignore this for aethetic reasons! Formula 2 gives the aperture of any pinhole/focal length combination. Most exposure meters are not calibrated in pinhole-size apertures so a conventional light meter used in conjunction with formula 3 will calculate a realistic exposure time to which you will need to add any reciprocity compensation for the film you are using.
When used in a spreadsheet, these formulae give a more useful set of tables. These are the ones I use for my 0.4mm to 0.8mm pinholes (all lengths are in millimetres); they print on A4 paper to be cut to A6 size:
- Tables 1 and 2: exposure compensations for meter set at f16, metered speeds from 1/250s to 2s
- Table 3: pinhole apertures
So you've spotted a scene that might make a good pinhole photo. What do you do?
decide what pinhole diameter to use. No decision if you've only got one size, otherwise you have to balance exactly the same factors you would if you were choosing a lens:
- do you want a separation of planes like a wide-angle lens, or a compression like a long-focus lens? The more wide-angle the effect, the smaller the pinhole you'll need.
- do you want to work near optimum distance for your pinhole to maximise the definition? If "yes", you are restricting yourself to a limited range of focal lengths for each pinhole. Maybe you can sacrifice definition for more mood?!
- what sort of exposure time is desirable? It may be that your subject dictates an exposure time (perhaps a portrait where you want short times, or running water where you want just the right amount of blur). If exposure time is most important to you, you need to work backwards through the following steps.
Here's the workflow I use. This is an aperture-priority approach. If you need exposure-time-priority, work backwards from step 5 to step 1:
- Fit the pinhole to your camera and compose the picture by moving the camera backwards and forwards or, if using a large format camera, rack the focusing control until the image looks correct on the screen. I use the 0.8mm pinhole for composing since this gives the brightest image, but it is still very dim compared with an f5.6 lens, so make sure you've got an effective focusing cloth! Then I switch to a smaller diameter for the actual exposure.
- Measure the focal length (mm). Look up the nearest focal length in Table 3: Pinhole Apertures. Go across the table to the column representing the pinhole you will use and read the aperture.
Example: I measure the distance from my pinhole to film plane as 128mm. I choose 130mm in the left hand column of table 1 and look across to the 0.5mm column where I see that the aperture is f260.
- Use an exposure meter to find the shutter speed of your scene at f16.
Example: you get a reading of 1/30s.
- Move to Tables 2 and 3 Pinhole Exposure Compensation and locate the nearest aperture in the left hand column corresponding to the aperture from step 2. Move along this row across the columns to the column corresponding to the metered shutter speed. The number in the table is the exposure you need to give your picture.
Example: the nearest aperture in table 2 to f260 (from step 2) is 250. Moving right to the 1/30s column shows that the actual exposure time should be 33 seconds.
- Compensate for reciprocity for the film you are using.
Example: you are using Kodak Tmax100 so you would need to give an actual exposure time of 45s.
The Pinhole Photography Ring has some useful Web sites. Analogue Photography Users Group has an alternative processes forum that includes pinhole topics. Alternative Photography has a section on pinhole photography.