Pinholes need to be very small to provide a useful image. Consequently the corresponding f-values are small, in most cases f:100 or smaller. This results in either very long exposures, or requires the use of very high ISO values. As we will see in the example images this is less of a problem than what could be expected because as the resolution of the pinhole is low, the images tolerate very strong noise reduction processing without losing there character or mood.
Another consequence of the very small size of the aperture is that dust on the camera sensor assembly becomes much more visible than when using glass lenses and larger apertures. Dust that is not visible at all in normal use becomes very visible when using a pinhole, requiring extensive use the a “heal tool” during file editing.
The positive side of using a small aperture is that depth of field is very deep. Pinholes cannot be focused like glass objectives. In contrast there is an optimal pinhole diameter for maximum resolution, which depends on wavelength (colour) of the light, and focal length. As a consequence of this, macro extension tubes can be used to increase the focal length.
The two Thingyfy pinhole objectives arrived today. They seem fairly well built and solid. They have a 58 mm filter thread and the MFT mount at the rear is part of the barrel. The finish seems to be black anodised inside and outside. They fit the camera mount just a bit tight, but nothing to worry about. The 26 mm focal-length Pinhole Pro with multiple pinholes, selected with a ring similar to an aperture ring with click stops, seems to me the most versatile and useful of the two. The range of pinhole sizes is broad (0.80 to 0.10 mm) and allows quite a lot of control over sharpness. It also has pinholes large enough to work nicely with “macro extension tubes” to obtain longer focal lengths. In this case the extension tubes are not used for closer focusing, but instead to increase the focal length.
The wide-angle 11 mm focal length Pinhole Pro S11 has a single pinhole, of a size slightly large for maximum resolution at its focal length, allowing its use with a short extension tube in addition to directly mounted on the camera.
When I came back home from the post office there was still enough light to take a few test photographs of clouds in the sky.
Pinhole Pro S11
With this objective vignetting is very obvious as well as some colour shift towards the edges of the frame. A pinhole will never be very sharp and at this very short focal length (wide-angle) the geometry of the light path results in strong vignetting. Pinholes are used for the “character” of the photographs they produce and vignetting and low resolution are what makes them interesting. Their limitations are specially noticeable in small sensor size cameras like the micro four thirds camera I use.
The Pinhole Pro S11 can be combined with a 10 mm extension tube to form a 21 mm f:150 pinhole.
With a focal length of 26 mm, vignetting is much less than with the wide-angle pinhole. By selecting the pinhole size, it is easy to control the (lack of) resolution to one’s taste.
With 16mm + 10mm Kenko DG macro extension tubes focal length is doubled to 52 mm.
This combination works satisfactorily resulting in a moderate teleobjective. It became too dark before I could try using the extension tubes individually. These give 36 mm and 42 mm as focal lengths when combined individually with the 26 mm Pinhole Pro.
All illustrations, text and measurements are of my own authorship, and copyrighted.
(c) 2018 Pedro J. Aphalo