Can I use M42 35mm-film lenses on Micro Four Thirds, and will the focal length change?
Asked 5/2/2019
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I have some M42 lenses from shooting 35mm film and I’m considering an Olympus Micro Four Thirds camera. I know simple adapters exist, but I’ve heard that a 50mm lens behaves like a 100mm lens on Micro Four Thirds. Does the lens’s actual focal length change, or is it just the field of view that changes because of the smaller sensor? If I adapt my existing lenses, is there any way to get a view closer to what they looked like on 35mm film?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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The focal length stays at 50mm, but the field of view will be that which you would get from a 100mm lens on 35mm film. Depth of field characteristics at a given aperture will be that of a 50mm lens.
There are special adapters, called focal reducers or speed boosters, that shorten the effective focal length (like the opposite of a teleconverter). Since these are optical devices, they will interfere with other lens characteristics, but not necessarily in a disadvantageous way (in some cases, resolution and contrast will actually improve, and you gain some lens speed). These come in a wide variety of prices and qualities, and are specific to a front and rear lens mount just as glassless adapters are. Hint: If you have legacy lenses with more than one mount, eg Canon FD and M42, look into possibilities like getting the FD mount version and using a M42 to FD adapter on top of it.
Originally by user58185. Source · Licensed CC BY-SA 4.0
user58185
7y ago
0
Generated from our catalog & community — verify before relying on it.
Yes, you can use M42 lenses on a Micro Four Thirds camera with an adapter.
The lens does not change focal length: a 50mm lens remains a 50mm lens. What changes is the field of view, because the Micro Four Thirds sensor is smaller than a 35mm film frame. So a 50mm lens gives a field of view similar to what a 100mm lens would show on 35mm/full-frame.
In other words, it’s not really becoming a 100mm lens; the camera is just capturing a smaller central portion of the image projected by the lens.
Depth of field characteristics at a given aperture remain those of a 50mm lens, per the community answers.
If you want a wider, more “normal” full-frame-like view, there are optical adapters called focal reducers or speed boosters. These reduce the effective focal length and can also increase effective lens speed, though they add glass and can affect image characteristics. A standard glassless adapter will not restore the wider field of view.
So: your M42 lenses are usable, but they will look tighter on Micro Four Thirds unless you use a focal reducer.
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