Tipster: How To Measure Exposure Times For Pinhole Photos


For World Pinhole Photography Day we're celebrating the magic of pinhole photography with our community. Today we want to talk about exposure time when doing pinhole photography, more specifically how to take a metering if you find yourself without a light meter. For this tipster we used the Diana F+ Glass Lens Set paired with a roll of Potsdam Kino B&W 120 ISO 100.

If you are new to pinhole photography, the first question that will arise is, how can I accurately measure exposure times? The main characteristic to keep in mind is that it requires a long exposure time. When dealing with long exposure, one of the first obstacles you will face is getting acquainted with the law of reciprocity.

Photos by Elisa Parrino

What is the reciprocity law?

The law describes the rules that govern the light hitting the film and the relationship between the shutter, the aperture, and the ISO of the film that determines a good exposure. The failure of this law is the term used to describe photographic film's non-linear response to low light exposure.

What it means is that once the light levels reaching the film drop below a certain threshold, the effective sensitivity of the emulsion decreases. This is because in chemistry, the longer time a reaction requires, the lower the power will be, until carried to the end of such process.

It is important to know the existence of such a rule if you are getting serious about long-exposure photography, as the time can be affected as early as 1 second of exposure time. However, it must be said that the quality of light is also important as the hour of the day.

But to what extent does the reciprocity law affect our film? Do we truly need to be worried from 1 second on? And what if you go out to shoot without a light meter that can tell you the exact exposure time needed? How can you calculate the compensation needed?

While browsing online, we found a useful chart designed by Richard Koolish that is an extremely handy tool to have if you need to know your exposure time but find yourself without a piece of technology to help you meter the situation.

To make this work, you must know the aperture size of your pinhole camera. That is the only mandatory piece of information. It is a simple wheel composed of three elements: shutter speed, ISO, and the f-number. Simply set the ISO of your film, with the lever point at the sun condition, and look at where your f-number is matching with the exposure time.

Photos by Elisa Parrino

As we wanted to test how accurate this exposure was, we didn't apply any other compensation. The ISO of our film was low (100 ISO) and since the hour of the shooting was in the middle of the day we trusted the calculation, and waited to see the results. From the moment that we opened the tank and saw the negatives we knew that the exposure was correct, and we were happy with the scans as well. The glass lens had given a good overall sharpness through the picture and although with a pinhole image it is never absolute, in these pictures it's good enough.

We are happy that this chart has worked well for us and that we now know when the exposure is between one second and three seconds there isn't a need for a drastic compensation. The exposure was correct thus the failure of the reciprocity law is not compulsory at this stage.

Which one is you favourite metering system when doing pinhole photography? Share your work flow in the comments below.

written by eparrino on 2023-04-30 #gear #tutorials #pinhole #medium-format #balck-and-white #120-film #world-pinhole-photography-day #potsdam-kino #diana-f-glass

Mentioned Product

Lomography Diana F+

Lomography Diana F+

Take timeless and dramatic photos on 120 film with the Diana F+. Create stunning soft-focused images and customize it with sweet lenses or even an instant back for additional effects and flexibility.


  1. eparrino
    eparrino ·

    @klawe Cool!

  2. stereograph
    stereograph ·

    Nice article,
    but with the glass lens on, it its not a real pinhole shot, @eparrino! :-)

    Actually the longer the exposure time is the more pinholy it gets,
    sharpness decreases with time due to atmospheric disturbances, water freeze, and people disappear.
    I like to put the camera on in low light conditioins for, lets say 3 or 4 hours,
    i don't need to care about anything, no Schwarzschild no ASA.

    Challenging it gets with exposure times between 1,2,3 minutes to 10 - 15min,
    here the reciprocity failure will take his biggest share, if you calculate wrong.
    Its always underexposure, so just let it sit longer and catch some more light!

    when i have 1 or 2 seconds i shot out of the hand and can even do multiple exposures:

  3. eparrino
    eparrino ·

    @stereograph Indeed the longer the better! You are right. The more challenge it is the more fun you'll can have when you see your negatives. But I hope that more people start to approach Pinhole photography, and are not scared about it, especially when if you start reading all the info available on the web, it can be overwhelming. So I wanted to start from something easy ;)

  4. astonuts
    astonuts ·

    @stereograph @eparrino I was to say the same and had a bug when I read "glass lens". I happen to use my Diana F+ with the glass lens and want to try that camera for its pinhole ability.
    Your comment about short times for reciprocity law failure is very interesting @stereograph Maybe I will start with longer exposures to avoid being disappointed.

  5. astonuts
    astonuts ·

    There's a interesting article for Diana use as pinhole here too :

  6. stereograph
    stereograph ·

    @astonuts Amy's Article is very helpful!
    Since i read it, i calculate my exposure also with f/128 for the Diana.
    My meter goes to f/90 when i shot with 100ASA
    i measure with 50ASA an have a proper reading on f/90
    plus Schwarzschild - Bam!

  7. astonuts
    astonuts ·

    @stereograph yes indeed ! Anyway I often measure with an app on my smartphone and some apps go much further than f/128 ...

  8. astonuts
    astonuts ·

    @stereograph but I haven't yet found an answer to this question : how do you frame ? Is the pinhole wider than standard lens ?

  9. trad69
    trad69 ·

    My calculator says Ilford on it but looks the same as the one shown - it usually seems to give the right answer. Recently used some half plate HP4 which expired in 1970s and didn't need to give any more. Likewise I have added markers for my various home made pinhole cameras. Still trying to find the right size pinhole for 35mm - my normal 18/1000in one which is fine for 120/LF 5x4-10x8 came out fuzzy on a Leica.

  10. trad69
    trad69 ·

    @klawe thanks for that I might have to buy a more precise small pinhole than I can make to do justice to the Leica with the drilled (non-original Leica) body cap which is probably quite a short distance.

  11. trad69
    trad69 ·

    Thanks- I hadn't thought of extension tubes will have a look for some (thankfully mine is a very old screw Leica)

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