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  • Writer's pictureJo

Maths & Magic

Updated: May 16, 2021

I am the proud owner of a small wooden box! It is a beautiful box, handmade in Slovenia and carved out of dark walnut wood. My box is special for it’s a magic box; every time I use it magic happens! My wonderful wooden box is a pinhole camera.

A pinhole camera is a lens-less camera. It is simply a box, or a canister that is made light-tight, with a tiny pin size hole at the front. The light passes through the pinhole imprinting an image on to film situated at the back of the box.

Pinhole cameras in one form or another have been around for hundreds of years. They can be made from anything, providing light cannot get in. There have been some very imaginative pinhole cameras made out of fizzy drink cans, biscuit tins, matchboxes – even turning rooms into giant pinhole cameras using blackout blinds at the windows.

There are 5 main characteristics unique to a pinhole camera:

  • Pinhole cameras have an almost indefinite depth of field and as such everything appears in focus.

Depth of field is the distance between the object nearest to you and the object farthest away from you that are in acceptably sharp focus in a photograph.

  • Although in focus, the images are soft for there is no lens to sharpen then – this gives them a dreamy effect.

  • The image on a pinhole camera is upside down.

In fact, all images on all cameras are inverted but on ‘proper’ cameras they have mirrors or prisms so that the image is shown the correct way around. Even the human eye creates inverted images, but the mighty and powerful brain does its magic and corrects the image for us – thank goodness!

  • Wide angle images stay rectilinear as there is no lens distortion: straight lines remain straight lines!

The glass in a camera lens bends the light to reach the camera sensor and the wider the field of view the more the bend. If you look at a wide-angle camera lens the glass is much more spherical in shape than that of a standard lens. This bend, or curve, allows the lens to capture a wide scene. However, the bending can cause distortion and lines will curve out at the end of the image. Pinhole is lens less so no distortion.

  • Exposure times are usually exceptionally long to allow enough light to get in through the teeny tiny hole. This can result in motion blur around moving objects and even the absence of objects that moved too fast. Sometimes you will often see ghostly apparitions (but let’s be clear, they really are not actual ghosts.....or are they?!).

Exposure time is the time the sensor (in digital photography) or film, as is the case here, is exposed to the light by the opening of the shutter.

Now don’t tell my wife but I have quite a few cameras (oops, I fear that might be too late!). These comprise of a few mirrorless digital cameras and a selection of film cameras in various formats. In my previous blog I expressed my enthusiasm for the processes involved in film photography and my love of the fact that film photography makes you slow down – makes you think more. Well, a pinhole camera takes that to a whole other level (as Greg and John like to say, repeatedly, on MasterChef!).

My walnut box, made by ONDU Pinhole and affectionately but not surprisingly known as Ondu, has a little window in the back that is revealed so that I can see what number negative I am on, on the roll of film. The pinhole itself is at the front of the camera and in this model it measures a miniscule 0.25mm in diameter. There are two knobs on the top of the camera for winding on the film and the whole thing is light sealed by magnets. And that’s it and I love it!

For a simple box there is still however a lot of work to be done and instead of the camera doing its thing - algorithms and microchips and all that techno wizardry – it requires my real-life brain to step up, which is an interesting challenge!

So, to take a photograph you must first measure the light. I use a light meter and measure the incidental light.

An incidental light reading measures the light that is falling onto the camera as opposed to the light reflecting off the scene.

A light meter made by Sekonic. The white bulb measures the incidental light.

The measurement is calculated using my highest f-stop number on my light meter, which is f/22.

An f-stop is the number that you see on your camera lens when you adjust the size of your aperture. F-stops are fractions, and so an aperture of f/2 is much larger than an aperture of f/22. The light is reduced or increased by stops. A small f-stop fraction is a large aperture that lets in a lot of light and a large f-stop fraction lets in a small amount of light.

The f-stop on a pinhole camera is calculated by dividing the diameter of the pinhole by the focal length (stay with me!).

This particular camera has an f-stop equivalent of f/160. This means I have to get the calculator out and do some sums that involve fractions and parentheses and even algebra! As well as giving me brain ache this will give me the correct exposure time for this camera, which can be anything from a fraction of a second up to several days! My longest exposure to date is 3 1/2 hours, which was taken in our living room one evening that was lit only by table lamps. But the sums haven’t finished here, oh no! Each make and model of camera film has a limit before “reciprocity failure” kicks in, so now I must do another calculation to account for that!

If you are using a lower speed film in daylight or taking an exposure at night, at some point you are going to start challenging the limits of your film’s light gathering ability. As light becomes scarcer, science says that there will a diminishing response to low light levels which is known as a film’s reciprocity failure.

So now I’ve exposed the light for an aperture of f/22, then re-calculated for f/160 and if the resulting exposure time is generally a second or more, I then calculate the allowance for reciprocity failure and … abracadabra … this gives the total amount of time that I should allow for the light to enter through the pinhole. Phew, I need a lie down!

Another issue that needs to be considered is how close to position the camera to the subject. There’s no viewfinder or screen to look through like a regular camera but I do have one fact to help me and that is, the closer in distance the film in the camera is to the pinhole means the wider the angle of the field of view.

Field of view is the maximum area that a camera can record an image of. This is normally related to the focal length of the lens (the distance between the lens and the image sensor of the lens when the subject is in focus) but of course in pinhole there is no lens and no sensor, so the equivalent is the distance in millimetres between the film and the pinhole.

My Ondo pinhole camera creates images of 6x9.

The 6x9 format is considered a classic look. Before the 1960s the 6x9 format was very fashionable. Due to its large negative size, it provided a lot of detail and its elongated shape suited many subjects: it was even a popular canvas size for artists. But as is the case with fashions they don’t last. The 6x9 was replaced by a new younger model, the daring 6x7, and as far as I am aware, other than in the world of pinhole, no more 6x9 cameras are produced today.

I know from the maker of this 6x9 that the distance between the film and the pinhole is 40mm, which will give a viewing angle of 103 degrees - so it’s quite a wide angle. This means I need to position the camera close to the subject matter. Ultimately where you place the camera comes down to guessing and experience. My Ondo has been balancing on rocks and logs and connected to big tripods and mini tripods and even clamped to railings and fence posts to get close to subjects.

Once the sums are done, and the camera is positioned then I flick back the piece of wood that is covering the pinhole (the equivalent of the shutter) and … wait - with my stopwatch ticking away the minutes or simply “one elephant, two elephants” accounting for the seconds!

I shoot both black and white and colour film and as it is 6x9 format a roll of film allows for just 8 images. Consequently, I try to not waste a single image. I send my films to a lab who develop and scan them for me and it’s always exciting receiving the email with my images attached because only then do you find out if you have been successful and if your calculations are right.

Again, I love the processes involved and the anticipation. I love the simplicity of the camera. I love having a small kit bag compared to when I take my other cameras out to play! It's true, I don’t like the maths - but it exercises my brain and gives me an enthusiastic sense of achievement when the results are good. If the images are not as I hoped, then it’s a lesson for next time.

I’m still new to pinhole and there is a lot of experimenting to do with exposures and composition. Below are some of the images I have taken to date with my Ondu. You will note straight away the softness but also the moodiness that often results because of that.

Pinhole images are a bit like Marmite – some people love them, others hate them, particularly when we are so used to photographs with pinpoint precision, clarity, and sharpness. I sometimes think though those digital images are too clinical: I want to make photographs that distinguish my work from that of other photographers and let’s face it, everyone is a photographer today with their phones at the ready.

I would love to hear what you think of my pinhole images so do let me know in the comments and if you want to see more of my pinhole portfolio do take a peek at my YouTube channel at

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1 Comment

Fascinating.. thanks for the explanation.... 'rectilinear' is a fab word.... new to me and now wondering how on earth I can work it into a non photography related sentence... there's a challenge...

But tell me Jo..... how many cameras do you have now..... 🤔

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