hassighedgehog Loc: Corona, CA

In 2002 when there was a solar eclipse in my area tried something similar (really made a camera obscura). Took a cardboard wine carrier and poked a hole in the bottom. Used that to focus the eclipse on to the flat side of my home. Took pictures with my first digital camera.

BebuLamar

Wanted to get a pinhole but they are quite expensive.

htbrown Loc: San Francisco Bay Area

Brass shim or even aluminum foil. A sheet of very fine (2000 grit) sandpaper on a flat surface. Dimple the foil with a needle or a pin, sand until a tiny hole appears. If you want to get fancy, you can get a no. 80 drill bit to make your hole. The smoother the edge of the hole the better.

Drill a hole in a camera body cap and glue or tape your new pinhole over it. You have a pinhole camera.

You can get fancier with how you mount the pinhole, but not much cheaper. You probably have everything you need but the sandpaper, which is the most expensive item on the list above. I can find fine sandpaper at my local hardware store. You might also find it at a store that caters to automobile bodywork.

Bipod

Thanks for filling in the details of the pinholes. Very interesting.

It's too bad we don't know either the projection distance when the cap was on the D300
or the exact numerical aperture. Body caps don't sit right on the flange, usually, and
the pinhole can be mounted on either the outside or the inside of the cap.

A pinhole diameter of 0.0889 mm (0.0035 inch) seems a bit small for that projection
distance (around 46.5 mm -- FFD of Nikon F-mount -- give or take a mm or two).

I'd expect something closer to 0.222 mm (0.0087 inch) for optimum sharpness at infinity.

The Stanford Pinhole Calculator 3.0 gives:- 0.252 mm (0.00992 inch). for subject at infinity.
https://web.stanford.edu/~cpatton/phcalc3.htm

Pinholes tend to be used most of the time for subjects at their hyperfocal distance or
further away. So infinity is usually the proper subject distance to use when chosing
the optimal pinhole.

Regarding the formulas, K is a dimensionless constant (like pi) -- no unit of measure.
(Unlike pi, experts disagree on the correct value for K!)

Wavelength and projection_length should be in whatever unit of length you want
for the pinhole diamter, typically millimeters or inches. This involves some big
numbers, so a scientific calculator is handy.

Bipod

It's really great that your high school taught optics.

Around 240 BCE, Erastosthenes used the hight of the sun at miday
at two places a known north-south distancer apart. Sounds like maybe
your students could do that.

Maybe you'll appreciate the significant differences between pinholes and lenses.
Pinholes do not converge any two rays onto a single point. So the term
"focal length" applied to a pinhole is just an analogy. (Yet it's everywhere
in the scientific lterature about pinholes.)

More to the point, there is a divergence of opinion even among
famous physicists as to the optimum pinhole size for a given camera.
George Airy got it wrong--as Lord Rayleigh points out. But Lord Rayleigh
got it wrong, too. You can read his original paper here:
http://idea.uwosh.edu/nick/rayleigh.pdf

In fact, optimum pinhole size is a compromise beween diffraction
(if the pinhole is too small) and circle-of-confusion (if the pinhole is too large).
You always get both an Airy disk (diffraction)--however faint--and a circle-of-confusion.
(geometric optics--because the pinhole diameter is larger than infinitesimal).

One interesting thing is that, when the subject is at infinity, the circle-of-confusion
is exactly the size of the pinhole! Parallel lines do not converge or diverge.

Manglesphoto Loc: 70 miles south of St.Louis

Thank you very much for information.
All of these calculations are way beyond me, However I will try larger dia. pinholes at a later date.

For all of the pinhole stabbers: Drilling the hole eliminates the need of sandpaper and allows for closer to round and a known diameter hole than poking with a needle, more expensive, and not as easy to find drill bits in these small dia., but some interesting results can be obtained with ragged edged or multiple holes.

Bipod

Laser etched pinholes are available commercially.

The size of the pinhole is crucial for maximum sharpness. It depends on the distnace from the
pinhole to the film or sensor (which in turn depends on the format), and the distance to the subject.

FF and smaller cameas require really tiny pinholes. A #80 drill diameter is 0.0135 in (0.343 mm).
This is too large for FF. Watchmakers's drills go down to smaller sizes. For a Nikon F-mount,
#90 0,0087 (0.221) is about right. I tried #80 and it was very unsharp. The Stanford Pinhole
Calculator 3.0 gives the best values of any of the many calculators I've tried.
https://web.stanford.edu/~cpatton/phcalc3.htm

To get a truly sharp pinhole photo, you need to go to medium or (better) large format.
I have a Kodak Hawkeye Brownie (120 film) that I plan to covert to pinhole (in a way that
doesn't damage the camera an dis reversible).

Pinholes don't have a true front focal length. Instead, they have a hyperfocal distance: any
subject at this distance or further are the same as at "infinity". So most pinhole cameras are designed
for this infinity focus. (But If you plan to take only close-up picture --at less than the hyperforcal distance--
then a smaller pinhole should be used.)

The pinhole itself has only two characteristics: diameter and angle-of-coverage. Everything else--
hyperforcal distance, image diameter, angle-of-view--depends on both the pinhole diameter
and the pinhole-to-film distance.

For best results, the same care should be exercised in making a pinhole camera as in making a lens
camera.. Most of the defects one sees in pinhole photographs--distortion, vignetting, light leaks,
excessive unsharpness--are due to bad designs and/or shoddy construction.

Of course, if one is going for a "lomography" look, that's fine. But a lot of people have the wrong
idea about pinholes: that they create aberrations and distortion. In fact, pinholes are totally free of
aberrations and distortion -- far better in this respect than any lens.

The very best lenses sold by Nikon and Canon have more aberrations and more distoration than a pinhole.