How to Find the Working Distance of Any Lens for Custom Camera Mounting

Over the years, cameras have slowly evolved into what we use today. However, just because you’ve changed cameras doesn’t mean you have to throw out all of your old lenses. Freelance photographer Mathieu Stern has turned this challenge into a career. From the modern day lenses to old large format lenses, Stern has figured out a way to adapt old camera lenses to fit on modern DSLR cameras. To help save money and provide new insight into your camera, he created this short video to show how you can adapt any camera lens to fit your camera with one simple trick:

Each manufacturer (Nikon, Olympus, Canon, etc.) has their own flange focal distance. In order to find the right lens adapter to mount a different lens, you have to be able to calculate this distance (i.e., the distance between the back of your lens and the camera sensor).

flange focal distance

Unfortunately, this information isn’t always readily available. To determine this information on your own, you will need a white surface, a ruler, a light source (e.g., window, lamp, etc.), and a camera lens.*

After obtaining the necessary supplies, prop up the white surface near the light source, and move the lens around to focus a projection onto the white surface.

how to find flange focal distance

Once you have the projection in focus, measure the distance between the white surface and the lens with the ruler.

finding the right lens adapter

Now, subtract the flange focal distance (the distance from the mounting flange to the sensor) from your last measurement (working distance). This will calculate the exact size of adapter you need to focus the lens on your camera.

*It’s important to note that although this technique works with most cameras, it isn’t foolproof.

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One response to “How to Find the Working Distance of Any Lens for Custom Camera Mounting”

  1. Jp says:

    Thanks for the great insight into this topic. It can be daunting for the average Joe to understand the concept.

    However, the method above is only a rough guide. There is a very high accuracy required when we talk about the distance of the lens to the sensor.

    Using the above method, the accuracy might be 0.5mm. Maybe more if the user is careful enough.

    However, even if you’re off by 0.1mm, you might lose infinity focus.

    I guess a better approach might be to set the lens to focus at its farthest distance (infinity focus) & then try to get a far part of the scene in focus in the sensor.


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