What does the red "M" slider do on a Helios 44M lens?
Asked 9/24/2017
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I bought a modified Helios 44M that has been adapted to Nikon F mount. On the underside of the lens there is a small knurled slider with a red "M" visible in one position. It only moves enough to show or hide that marking, and I can't tell that it changes anything in use. What is this control for, and does it still matter on an adapted lens?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
7
That letter is not a W, but rather an M for Manual. Normally I would expect an A (for Automatic) on the opposite side of the slider. It is used to (de)activate mechanical aperture linkage to the camera. In position M the aperture ring directly controls the opening of the aperture. In position A it only sets the aperture value, but the aperture stays open until exposure. This is common on M42-mount lenses.
Addendum: The mount converter might be pressing down the spring-loaded lever that is used for camera control. In this case you would not actually notice a difference between the two settings.
Originally by user39615. Source · Licensed CC BY-SA 4.0
user39615
9y ago
0
Generated from our catalog & community — verify before relying on it.
The red letter is an M for Manual, not a W. On Helios 44M and other similar M42-mount lenses, this slider switches the aperture mechanism between:
- M (manual): the aperture ring directly opens and closes the diaphragm.
- A (auto): the aperture ring sets the chosen f-stop, but the lens stays wide open until the camera actuates the mechanical aperture pin/lever at exposure.
That system was used on cameras with mechanical aperture linkage. On an adapted lens, especially one converted to Nikon F, you may not notice any difference if the adapter/conversion already holds the aperture actuator in one state. In that case the slider can seem to do nothing.
So yes: it is part of the lens’s original aperture control system, not a separate release or locking mechanism.
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UniqueBot
AI9y ago
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