[danlam]

Hi all,

I am sort of confused on how to use Auto mode on the lenses. Would someone please be able to walk me through it?

Cheers

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Last edited by danlam; 01-07-2017 at 03:56 AM.

[arnold]

Auto in this case only means the lens will automatically stop down the the selected aperture when the shutter is tripped. It allows you to do your viewing with the lens wide open. That is the normal position. Manual is for those cameras that can't trip the auto pin on the lens.
The manual switch on the camera is used to stop the lens down to get a light meter reading for Spotmatics earlier than the "F" model.

[stevebrot]

First rule with your S-M-C Takumar lens:

• Don't attempt to move the A/M switch on your lens unless it is mounted to the camera, has a rear lens cap attached, or has a K-mount adapter mounted. The reason is complicated, but forcing the switch when not mounted may permanently damage the lens aperture mechanism.

Now, with that out of the way, here are the bullet points:

• The A/M switch enables/disables the lens' automatic aperture
• In the M (manual) position, the aperture is fully manual, meaning it is stopped down all the time
• In the A (auto) position, the aperture actuation is "automatic" meaning that when mounted to a supporting camera the lens will stop down prior to exposure and open again automatically after the shutter closes. This is done using the silver pin that protrudes from the back of the lens. Compatible cameras have a "flipper" in the mirror box that strikes the pin during the exposure sequence.
• Auto aperture actuation has nothing to do with exposure automation or automated aperture control
• Adapted lenses will stay wide open unless the A/M switch is in the M position

Regarding metering:

• Most M42 screw mount bodies with TTL metering use stop-down metering, meaning that the body will stop the lens down when the meter switch is turned on
• S-M-C and SMC Takumar lenses support wide-open metering on some bodies (e.g. Spotmatic F, Spotmatic ES, Spotmatic ESII, and Electro Spotmatic) with no stop-down required. The first rule (see above) is due to this ability.

Does this help?


Steve

[danlam]

First rule with your S-M-C Takumar lens:

• Don't attempt to move the A/M switch on your lens unless it is mounted to the camera, has a rear lens cap attached, or has a K-mount adapter mounted. The reason is complicated, but forcing the switch when not mounted may permanently damage the lens aperture mechanism.

Now, with that out of the way, here are the bullet points:

• The A/M switch enables/disables the lens' automatic aperture
• In the M (manual) position, the aperture is fully manual, meaning it is stopped down all the time
• In the A (auto) position, the aperture actuation is "automatic" meaning that when mounted to a supporting camera the lens will stop down prior to exposure and open again automatically after the shutter closes. This is done using the silver pin that protrudes from the back of the lens. Compatible cameras have a "flipper" in the mirror box that strikes the pin during the exposure sequence.
• Auto aperture actuation has nothing to do with exposure automation or automated aperture control
• Adapted lenses will stay wide open unless the A/M switch is in the M position

Regarding metering:

• Most M42 screw mount bodies with TTL metering use stop-down metering, meaning that the body will stop the lens down when the meter switch is turned on
• S-M-C and SMC Takumar lenses support wide-open metering on some bodies (e.g. Spotmatic F, Spotmatic ES, Spotmatic ESII, and Electro Spotmatic) with no stop-down required. The first rule (see above) is due to this ability.

Does this help?


Steve

Hi Steve,

Thank you very much this is very helpful.
Is there a way of checking whether or not the first rule has been broken? Will I see evidence in photos taken? How would I know that the lens aperture mechanism has not been damaged permanently?

[stevebrot]

How would I know that the lens aperture mechanism has not been damaged permanently?

If it works properly on the camera.


Steve

[stevebrot]

There is more:

On your Spotmatic (pictured in your post), you will generally shoot with the A/M in the A position. The flow goes like this:

• Frame your subject
• Move the meter switch to the on position. The lens will stop down.
• Move the aperture ring or shutter dial to center the meter needle. Move the meter switch to the off position to open the lens back up.
• Focus and shoot
• Repeat the above step until either the light or the subject changes.

Steve

[stevebrot]

If it works properly on the camera.


Steve

Sorry for being short. With the lens on the camera:

• Aperture ring moves freely
• A/M switch moves freely
• Lens stops down for exposure when switch is in A position
• Lens stops down when meter switch is turned on and A/M is in A position
• Lens remains stopped down when switch is in M position

Steve

[stevebrot]

Most of the above (except the first rule) is in your camera's manual. It is available at:

Pentax Manuals: M42 Manuals

There are both 20 page and 36 page versions for Honeywell Spotmatic and 20 page for Pentax Spotmatic.


Steve

[danlam]

Most of the above (except the first rule) is in your camera's manual. It is available at:

Pentax Manuals: M42 Manuals

There are both 20 page and 36 page versions for Honeywell Spotmatic and 20 page for Pentax Spotmatic.


Steve

Cool thanks very much for all the info Steve. Very helpful!

[goatsNdonkey]

I just want to say that I like that lens pictured on your Spottie! It was my first big upgrade for my Ricoh TLS Singlex slr, when I replaced it's f2.8 Ricoh normal lens with a Super-Takumar 55mm f1.8 picked up used at Central Camera in downtown Chicago, in the late 1970s!

[danlam]

I just want to say that I like that lens pictured on your Spottie! It was my first big upgrade for my Ricoh TLS Singlex slr, when I replaced it's f2.8 Ricoh normal lens with a Super-Takumar 55mm f1.8 picked up used at Central Camera in downtown Chicago, in the late 1970s!

Cheers, I do not really know much about lenses or photography at this point - I only got into this around three months ago - I bought a whole bunch of Pentax SLRs from a thrift store and turned out that they worked and the lenses were good.

[Xmas]

Cheers, I do not really know much about lenses or photography at this point - I only got into this around three months ago - I bought a whole bunch of Pentax SLRs from a thrift store and turned out that they worked and the lenses were good.

Read manual, buy a film and a battery, shoot dog gfriend or wife... local mini lab prints Etc.

[stevebrot]

Read manual

Important!

and a battery

The original batteries were now illegal mercury button cells. The drop-in replacement is a 387S silver cell or similar. There is a voltage difference from the original, but the Spotmatic circuitry is minimally effected under most light conditions.

Pentax Asahi Spotmatic Film Camera Batteries at Batteries Plus Bulbs

Steve

[danlam]

Important!



The original batteries were now illegal mercury button cells. The drop-in replacement is a 387S silver cell or similar. There is a voltage difference from the original, but the Spotmatic circuitry is minimally effected under most light conditions.

Pentax Asahi Spotmatic Film Camera Batteries at Batteries Plus Bulbs

Steve

I replaced the batteries with some energizer battery which makes the light meter work - I heard that the reading may not be as accurate as the original merc batteries.

[Xmas]

Important!

The original batteries were now illegal mercury button cells. The drop-in replacement is a 387S silver cell or similar. There is a voltage difference from the original, but the Spotmatic circuitry is minimally effected under most light conditions.

Steve

My three spots are within 1/3 stop of OM4 & Weston II bright day to indoors silver, alkaline or zinc.
But the battery needs to be in serviceable condition, silver or zinc preferred. Most Pentax Film SLR used differential circuits and don't need a mercury cell.
The photo resistor cells can age and be replaced and calibrated.