[santinowuzhere]

Hello everyone,

I have a Super Multi Coated Takumar 1.8/55mm lens, and I'm afraid I don't really understand whether to keep it on automatic or manual mode.

I'm currently using it on a Praktica LTL, but plan on eventually using it with my Spotmatic SP.

Mainly, I'm afraid of accidentally damaging the lens by messing with a switch that I'm unfamiliar with.

How exactly would this switch affect shooting, particularly on older bodies like the Praktica LTL or SP?

I apologize in advance for my ignorance. I've tried google beforehand, but I'm still not fully understanding the feature.

[boriscleto]

Using it on a M42 body with a aperture pusher, just keep it on Auto. The S-M-C lenses have a lock that will keep it on Auto unless a pin is depressed on the back of the lens. This is to keep it from being switched to Manual on a SP F or ES.

[stevebrot]

I'm currently using it on a Praktica LTL, but plan on eventually using it with my Spotmatic SP.

Mainly, I'm afraid of accidentally damaging the lens by messing with a switch that I'm unfamiliar with.

Leave the switch on A for both your Praktica and future SP cameras. The only use case for M is with Bellows or extension rings or when adapted to other mounts. In fact, it is best practice with SMC/S-M-C lenses to leave it on A almost all the time. The only time it is safe to move it from A to M is when the small interlock pin on the lens' mount face is depressed, such as by a rear lens cap, a mount adapter, bellows, other similar. Moving from M to A is always safe. Never force the A/M switch.

Camera cautions:
Don't move the switch when mounted to the SP F, SP ES, SP ESII, or Electro Spotmatic. Those models do not depress the interlock pin.
Some non-Pentax cameras have screws on the mount face that may foul the interlock pin on SMC/S-M-C lenses. Removal of the lens if fouled may be difficult in the extreme. Your Praktica has a smooth mount and poses no risk. (Just tested on my LTL 3... )


Steve

[MossyRocks]

With the spotmatic you can use it with the switch on auto, on the Praktica LTL I don't know what it supports so I would probably use it on manual to avoid wasting film.

[othar]

In addition to the comments so far:
The A/M switch on M42 lenses allows closing down the aperture of the lens with cameras that don't have an aperture pusher (or adapters that don't push the aperture pin in by default), otherwise those cameras could use this lens only wide open

[marcusBMG]

fyi:

M42 Lens Aperture Control on Modern DSLRs : 3 Steps - Instructables