Digital Pin Hole Photography


Earlier this year it was Pin Hole Photography Day, as I did not have the time to construct a camera, I decided to take a few shots with my first digital camera body. I found a body cap drilled out some years ago with a Pin Hole chip for use on a Eos film body, so I made and attached a new Pin Hole chip* as shown above.
(inset shows a way of trying to 'measure' the diameter of pin hole by scanning chip and a reference scale. scan and then view at 10x and use same scale 1 division will now =0.1mm)*

I took a number of shots first using a 28mm lens then the Pin Hole which was approximately the same focal length. On inspection of the images I was struck by the marks which only appeared on the Pin Hole images as can be seen below.

I have enlarged a section to show them better.


The only explanation I can offer is that as the Canon 300D sensor has a number of filters sandwiched in front of its sensitive surface so any 'crud' would be held some distance from this 'back focal plane' upon which the image is focused.

The image produced by the Pin Hole is a function of the focal length, pinhole size and shape i.e. a diverging package of light so any 'crud' on the surface would cast a shadow onto the sensor as I have attempted to illustrate below.

Whereas the lens is focusing a cone of image forming light around the crud the wider the aperture the wider the cone and hence the less defined the shadow cast.


I used RAW capture to minimise any smoothing due to the averaging of jpg algorithms.
You could use a lens selecting the smallest aperture possible and shoot against a uniform background overexposing by say 1 -2 stops which helps to make dust more visible, but a Pin Hole works even better !
I recommend using both, the Pin Hole gives you early warning and costs so little and you can use it to produce 'Pin Hole Images'

Phil G



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 * ref 'Images Without Lenses' section for more comprehensive notes on Pin Hole Photography

NB. The use of a filter or slip glass over the sensor is possibly a design feature to reduce the effect of dust on the image in a similar way to how a diffusion enlarger reduces the effect of dust etc... on a negative.