Sunday April 27 was Worldwide Pinhole Photography Day.
Pinhole Photography means capturing images without the use of any lens, and the pinhole is all there is to refract the light from the subject onto the image plane. Think of an infinite number of overlapping rays of light being channeled through the tiny hole, coming from myriad points of the subject, then spreading back out again to duplicate the image of the subject onto a flat surface. That surface can be a projection screen of some sort, a piece of light sensitive film, or a digital light sensor plate.
The smaller the pinhole, the sharper the possible resolution of the image.

I used a 0.3 mm hole in a piece of aluminum sheet from a disposable pie pan, mounted into a Pentax body cap. Front mount plane on a Pentax DSLR is about 30 mm from sensor plane. With a 20 mm extension, that brought my hole to imaging plane distance to 50mm (equivalent to "focal length" in optics language), for an effective yield of f/167.

With a conversion chart, I was able to calculate my exposures. Hand meter showed about f/8 @ between 1/30 and 1/60 second for my setups, @ asa 800. So my pinhole exposures @ f/167 were in the range of between 10 and 20 seconds... I had camera body on tripod, with remote release cable, and mode set to "B."

For subject matter, I just used small objects artound the house and studio.

Interesting thing, at such a small aperture and great depth of field, every single mote of dust on the camera's CCD sensor showed up clearly in the images.

Please click on thumbnails to see enlarged.
All images are ©2014 E. J. Kowalski.