Shoot with a Pinhole Lens + CHEAT SHEET!

NOTE: If you’re just interested in the cheat sheet, here it is! I can 100% guarantee this cheat sheet will give you nearly some of if not most of the possible solutions to the normal-ish shutter speed adjustments necessary to probably make you more successful at getting a close exposure to what is needed.

For those of you who are here to learn. Keep reading.

How Pinholes Work

This is a short albeit technical post on the topic of pinhole photography.

Pinhole photography is a style (field, perhaps) of photography where instead of using a traditional glass lens that refracts and focuses light to create a sharp crispy image and allows for different apertures and focus depths, you use a tiny little hole to allow light to pass into a camera body. The pinhole, because it is so small, allows for an image to be exposed on either a sensor or film.

When you think about it, it’s quite a marvelous approach to photography. It is simple and removes one of the heaviest pieces of the camera (the lens) making even my beefy medium format film cameras feel lightweight.

A pinhole will generally have a focal length equivalent to the distance of film plane to lens mount. On my Pentax 6x7 (which has a dedicated 3D printed pinhole “lens”) that’s roughly 95mm (48mm in full frame equivalence). However, because a pinhole is so tiny and allows such little light to pass through the camera, you will not be able to frame and compose your photo, so it’s a fun guessing game.

The MAJOR Challenge with Pinholes

One of the major issues we face with pinhole photography is that standard meters don’t have aperture measurements as narrow as a pinhole. Thus, we have to do some calculations to find the right shutter speed otherwise our images will all be badly or unpredictably exposed. I’ve seen several sights that give averages. (i.e. If it’s bright and sunny, expose for 1 minute, if you’re indoors, expose for 20 minutes.)

Personally, I find that type of photography anxiety inducing. I like to make a conscious effort to get as close to my vision of exposure before I pull the trigger. I’ve wasted too many rolls of film through carelessness or ignorance.

With every pinhole size, ISO choice, lighting situation, etc. adjustments need to be made.

Shutter Speed Adjustment

Where we are unable to adjust the pinhole (our aperture) as a fixed measurement, we are forced to make adjustments of shutter speed as those other parameters change. If you load a roll of film in your camera (like I do) you’ll have to stick with that ISO for the duration of the roll. As the lighting or scene changes, then you have to be ready to adjust shutter speed in order to expose the scene to your personal desire.

But how? Like I’ve already said, a standard light meter doesn’t have an aperture setting as narrow as a pinhole, and how do we even find the pinhole aperture f-number to make metering adjustments?

Finding Your Aperture Equivalent

There is a not so simple calculation that we have to use to figure out the aperture in f-numbers of the pinhole. Without this number, we can’t compare it to standard aperture sizes (f/5.6, f/11, etc.)

The diameter of my pinhole on my lens is 0.4mm. Using that number and the “focal length” of my lens, I can find the aperture. Use the following equation:

f/d = a

where f = focal length and d = pinhole diameter, let’s solve for a = aperture.

In my situation, 95 divided by 0.4 which equals 237.5. So the pinhole I am using on my Pentax 6x7 is an f/237.5, which doesn’t technically exist in the world of aperture sizes but neither do pinholes.

The Extension Factor

Now that we know your relative aperture, we can pretty easily discover the factor needed to increase our shutter speed to an appropriate length. Use the following equation:

(a/m)^2 = extension factor

where a = pinhole aperture and m = metering aperture.

I’ll take my 237.5 pinhole aperture, divide by whatever aperture I want meter with (f/22 in this case) and then square the result. What I’m left with is my extension factor of 116.5. That means that when I meter at f/22, all I have to do is multiply the calculated shutter speed by 116.5 and I’ll get the new shutter speed that will work with my 0.4mm pinhole.

I suggest putting together a cheat sheet of your own or using mine right here.

Conclusion

Pinhole photography, just like any other “fringe” photography style (ICM, Polaroid, etc.) is about mood, story, shape, and style. There is real power in those to help captivate a viewer. It is well worth experimenting with these outlier styles from time to time. They help stretch your creative brain and also re-inspire you with a fresh approach. Not everything has to be super sharply in focus with clear details and an obvious compositional approach. Let’s make photography fun again with a simple little pinhole.

-Jude