Small-Format Pinhole Revisited

This morning I finally ordered the drill bits I need to make some pinholes. Even though I’m very happy with my Lensbaby pinhole optic, I can get wider with a body-cap pinhole, which is also much more compact.

My original plan was to add a 46-52mm step-up ring to the cap so I can add a filter. I’ve read that dust can potentially enter the pinhole and find it’s way onto the sensor, something that can’t happen with the Lensbaby, as its pinhole is printed on clear film. However, I’ve decided against that for the time being, as the area of the pinhole will likely be several magnitudes smaller than any gaps in the average lens.

I also planned on mounting the pinhole plate directly to the underside of the body cap, which means that the pinhole will be 48.5mm from the film plane, requiring a .26mm pinhole. This would be a good focal length for a “normal” angle of view. However, without interfering with the mirror, I can easily recess the pinhole into the body so that the distance is 37.5mm, making for a wider angle of view. That would require a .22mm pinhole. On an APS-C sensor camera such as the Nikon D90 DX format, it would be an approximate focal length of 56.25mm, considerably wider than the Lensbaby at 75mm (50mm x 1.5).

Large Format
I also plan on building some new 4x5 pinhole cameras, one 75mm “wide” (24mm equivalent focal length in the 135 format) and one 150mm “normal” (45mm equivalent in 135 format). These will require .32mm and .45mm holes respectively.

Medium Format
As good as large format pinhole photography is, medium format using 120 film is much more convenient, and less expensive to process. For this, I plan on buying the Holga 120WPC:

Holga 120WPC 6x12cm Pinhole Camera

Its 6x9 and 6x12 formats should provide plenty of area to develop a nice, “sharp”, detailed pinhole image. I’ve seen some really nice examples from this camera, so I feel it’s worth a try.

To make the pinholes, I’ll sandwich several sheets of thin brass painted on one side with superflat black paint between some thin sheets of plastic, and drill them together to make some pinhole blanks. This will prevent the pressure of the drill from distorting the hole in the very thin brass, and prevent the paint from filling the hole. I could also try drilling them first and painting them afterwards, and using the drill to open the hole back up. Then I can trim the plates to suit, and mount them with gaffer’s tape as needed.

For the 4x5 cameras, I’m toying with the idea of making matching body cap pinholes of the same focal length using a tube as an extension. These will not be for picture taking, but for judging exposure. Film has a characteristic known as reciprocity failure, meaning that its sensitivity to light is not linear; the longer the exposure, the less light it absorbs. This means I can use my Nikon N80 to take test shots with the same film stock as 4x5. I can then document the results so that I can take a meter reading and know, with a fair amount of accuracy, what the proper exposure is including the reciprocity factor. At this point, film is too precious to waste, especially 4x5.