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Mathieu Stern, the “weird lens guru,” recently published this video in which he removes the lens from a Vest Pocket Kodak camera and mounts it on a Sony A7iii. In the description of the video, Stern says only that the lens “was mounted using m42 [helicoidal] adapter + M42 to C mount adapter + rubber bands from [an] old bike tire.”

I’m interested in buying one of these old lenses and using it with my Canon EF-M mount camera. Can anyone tell me more specifically what kind of helicoid adapter I’d need? (It’s easy to find adapters that go from M42 lenses to EF-M cameras, so adapting the lens to the M42 mount would effectively answer my question.)

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While I agree that it is fun to adapt "weird" lenses, I also agree with Alan Marcus' implication that there are better lenses to adapt.

  • The Camera Wiki page about the Vest Pocket Kodak states that the lenses used on those cameras were about 72mm f/6.8. That gives you a FOV equivalent to about 115mm on a full-frame sensor. Some models have faster apertures (f/4.9), but are attached to more complicated mechanisms that would be more difficult to disassemble and adapt.

    This can be somewhat ameliorated by using a focal reducer in your adapter stack. This would "convert" the lens into a 52mm f/4.9, which is similar to the long end of a typical kit lens.

  • Shots in the video that were made with the adapted lens appear slightly blurry and heavily processed. Another issue with old lenses is veiling glare caused by insufficient or absent lens coatings. If you want a character lens, these features are great. Otherwise, it could be disappointing.

If you'd still like to adapt the lens, the main task is to get the right flange-focal distance. It appears fairly long for this lens. Some components to consider:

  • M42-to-EF-M adapter, focal reducer, or helicoid adapter.

    • The FFD of EF-M and Sony E mounts are the same (18mm). So the length of this component should match that shown in the video.
    • Since you are using a crop-sensor camera, I'd favor using a focal reducer. Though costly, it could be worthwhile if you have other M42 lenses. You could also use an EF-to-EF-M focal reducer with M42-to-EF adapter ring. The advantage of this option is adapter rings are available for other mounts (NF, OM, PK, C/Y).
  • M42-to-M42 helicoid, which you will use to focus. The video appears to show a 17-31mm helicoid. A shorter 12-19mm is also available. You can estimate the length you'll need by free lensing. (Search "M42 helicoid" on your favorite auction site.)

  • M42 body cap with appropriately sized hole drilled into it. Wrap rubber bands or tape around the end of the lens to hold it in place. If you don't want to wait for shipping, the cap of the 1L bottles of some sports drinks also fits M42. (It is held in place by friction. Here is a photo.)

Another issue is the shutter mechanism. I cannot tell from the video whether the shutter speed is adjustable. There are two options:

  • Set ISO and a long exposure on the camera. Set aperture and shutter speed on the lens.
  • Keep the lens shutter open and use the camera shutter to expose the image. This is the more convenient option. However, I cannot tell from the video whether the shutter has a bulb mode or if it would have to be disassembled. It's probably easy enough to figure out once you have lens in hand.

Here are relevant screenshots from the video for reference:

remove lens 1 remove lens 2 adapter + helicoid + cap + rubber band shutter release

  • What sports drink has caps that have an M42 outer thread? – rackandboneman Aug 29 at 7:50
  • @rackandboneman The bottle cap does not have outer threads. However, it does fit into the M42 mount. It is held in place by friction. Here is a photo. – xiota Aug 29 at 8:12
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The Kodak Vest Pocket cameras were made in 120/620 film size, likely a 100mm lens. The 127 film size models, likely 75mm. These were cameras made for black & white film, the lenses were not well color corrected. Films in that era were sensitive mainly to blue light, no need to color correct to bring the three primary colors to the same focus. Why not mount a more modern camera lens?

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    Why adapt any lens? Because it’s fun. – bdesham Jul 30 at 0:04

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