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05-23-2016, 10:59 AM   #1
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Spotmatic ESII problem. Lens locked in AUTO.

I have one of these sn 6652362.

The problem is that every SMC and Super Multi Coated Tak I own will not switch from AUTO to Manual when fitted to this camera. Every one of these lenses switch just fine when they have a rear cap on. Every one of these lenses switch just fine when fitted to another Spotmatic. The mounts do not appear to differ in any way.

I know about the tiny pin just outside of the screw threads.

Any thoughts or suggestions?

I'm baffled.

aoeu

---------- Post added 23rd May 2016 at 14:01 ----------

I doubt that it matters but my ESII is Honeywell branded and black.

05-23-2016, 11:20 AM   #2
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I have an ES, and it works the same way. Your camera isn't broken--it's designed to work that way!

The ES, ES II, and Spotmatic F have a little lever on the inside of the lens mount for open aperture metering, and S-M-C and SMC Takumars have linkages that connect to that lever. A few very late Super Takumars have that linkage also. There's also a little button on the back of each open-aperture-metering lens that has to be pressed in for the lens to switch to manual aperture mode. It just so happens that most lens caps push that button in. On the ES, ES II, and maybe the Spotmatic F, there's a step or groove cut into the lens mount so that the button is not pressed in, locking the lens into automatic aperture. Apparently they felt that open aperture metering meant you never should have to stop the lens down if it was compatible, though there is still a stop-down switch on the left so you can use older Super-Takumars. Since the original Spotmatic and the SP II don't support open aperture metering, they don't have the little groove and the later lenses will happily switch to manual aperture on those cameras.

The little button on the back is also the reason why open-aperture-metering Takumars shouldn't be used with the Mamiya-Sekor TL/DTL cameras: the button will jam in the screw holes on those cameras' lens mounts.
05-23-2016, 11:29 AM   #3
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I tried to measure the difference

in the mount between a Spotty and my ESII. With brass I didn't measure a distance differential.

In the next few days I'm going to look for my depth micrometer.

Why would Pentax decide not to allow manual switching?

More to my point what did Asahi do to prevent lens A/M switching? How?
05-23-2016, 12:23 PM   #4
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QuoteOriginally posted by aoeu Quote
in the mount between a Spotty and my ESII. With brass I didn't measure a distance differential.
They are the same, except that the ES II has a "step-down" at the inner margin of the mount that allows the pin to extend. This should be immediately obvious on examination.

QuoteOriginally posted by aoeu Quote
Why would Pentax decide not to allow manual switching?

More to my point what did Asahi do to prevent lens A/M switching? How?
If you know about the tiny pin, then you know that the A/M switch will not work unless the pin is depressed. The A/M switch is defeated to avoid accidentally screwing up the aperture-priority exposure automation and metering in general. That sort of feature is fairly standard for cameras that support open aperture metering. With non-SMC/S-M-C Takumar lenses, the A/M switch works the same as on Spotmatic and Spotmatic II bodies. Use the meter switch if you need DOF preview.


Steve


Last edited by stevebrot; 05-23-2016 at 01:01 PM.
05-23-2016, 12:30 PM   #5
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When you look at the lens mount flange on the camera body, on the inner circumference, there is a step or groove machined into the flange. This groove is just wide enough to clear the pin on the Takumar lens that needs to be depressed for the lens to be shifted into manual mode. I had to look at everything a couple of times to figure it out. As mentioned, this is a feature of the ES series and the Spotmatic F.
05-23-2016, 12:38 PM   #6
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I see it. My question is both why and how?.

What disambiguates the two seemingly similar physical M42 mounts?

aoeu
05-23-2016, 12:49 PM   #7
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QuoteOriginally posted by aoeu Quote
I have one of these sn 6652362.

The problem is that every SMC and Super Multi Coated Tak I own will not switch from AUTO to Manual when fitted to this camera. Every one of these lenses switch just fine when they have a rear cap on. Every one of these lenses switch just fine when fitted to another Spotmatic. The mounts do not appear to differ in any way.

I know about the tiny pin just outside of the screw threads.

Any thoughts or suggestions?

I'm baffled.

aoeu

---------- Post added 23rd May 2016 at 14:01 ----------

I doubt that it matters but my ESII is Honeywell branded and black.
Look at the lens while the aperture is set to something like f/22 and fire the shutter. It should stop down at the moment of the exposure just like a K mount M series or K series lens. At least that's my understanding.
05-23-2016, 12:55 PM   #8
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QuoteOriginally posted by UncleVanya Quote
Look at the lens while the aperture is set to something like f/22 and fire the shutter. It should stop down at the moment of the exposure just like a K mount M series or K series lens. At least that's my understanding.
You misunderstand my question.
Switchiing from A to M is forbidden in this case.

Peace?
aoeu

05-23-2016, 01:13 PM   #9
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QuoteOriginally posted by Stevopedia Quote
The little button on the back is also the reason why open-aperture-metering Takumars shouldn't be used with the Mamiya-Sekor TL/DTL cameras: the button will jam in the screw holes on those cameras' lens mounts.
There is a "hack" that allow (sort of) safe mounting. With the rear cap on, put the A/M switch in the M position. Doing so will retract the pin and the lens will clear the screw hole. Care must be taken when removing the lens, however. The switch must be set BACK TO THE M POSITION to avoid jamming on dismount.


Steve
05-23-2016, 01:22 PM   #10
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QuoteOriginally posted by aoeu Quote
What disambiguates the two seemingly similar physical M42 mounts?
See miner74's comment copied below...

QuoteOriginally posted by miner74 Quote
When you look at the lens mount flange on the camera body, on the inner circumference, there is a step or groove machined into the flange.
QuoteOriginally posted by aoeu Quote
My question is both why and how?
How? The little pin extends into the space made by the step, locking the A/M switch. The step is missing on all Pentax M42 bodies except Spotmatic models F, ES, ES II and Electrospotmatic.

Why? See my comment copied below...

QuoteOriginally posted by stevebrot Quote
The A/M switch is defeated to avoid accidentally screwing up the aperture-priority exposure automation and metering in general.
Again...this sort of interlock is standard for open-aperture meter cameras. You don't want the camera applying a bias to the meter* if the aperture is stopped down. That is why DOF preview levers/buttons are always spring-loaded. I suggest that you re-read the replies on this thread.


Steve

* What the body does in response to movement of the aperture coupling.

Last edited by stevebrot; 05-23-2016 at 01:38 PM.
05-23-2016, 01:37 PM   #11
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QuoteOriginally posted by UncleVanya Quote
It should stop down at the moment of the exposure just like a K mount M series or K series lens. At least that's my understanding.
That is the automatic aperture feature which is different than open-aperture metering. All Pentax bodies from the model K (1958) on support automatic aperture.


Steve
05-23-2016, 03:24 PM   #12
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QuoteOriginally posted by aoeu Quote
You misunderstand my question.
Switchiing from A to M is forbidden in this case.
I don't think I misunderstood the stated problem - I do think I misunderstand the issue. What is the value of using M if you have an open aperture metering camera? Why would you want to switch to M mode while using this lens on this camera?

QuoteOriginally posted by stevebrot Quote
That is the automatic aperture feature which is different than open-aperture metering. All Pentax bodies from the model K (1958) on support automatic aperture.
The distinction is lost on me. But if I understand I think you would meter with the aperture closed down and then reopen it (or leave it closed) until ready to shoot then the camera would close it (if not wide open) and take the picture. In this case the camera never closes it until the picture is made - correct? Is there a DOF preview option on these cameras? That's the only reason I can think of for wanting to stop down when the meter already works correctly while open.
05-23-2016, 07:05 PM   #13
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QuoteOriginally posted by aoeu Quote
You misunderstand my question.
Switchiing from A to M is forbidden in this case.

Peace?
aoeu
On Pentax M42 cameras with full aperture metering when using SMC lenses, switching from Automatic to Manual aperture is accomplished by using the stop-down/meter switch on the left side of the mirror box.
05-23-2016, 07:33 PM   #14
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QuoteOriginally posted by UncleVanya Quote
The distinction is lost on me.
Not a problem. All open-aperture meter cameras are auto-aperture, but not all auto-aperture cameras feature open-aperture metering.

I shot for 12 years with a stop-down meter camera (e.g. Spotmatic). Without automatic aperture, it would have been a pain. With auto-aperture, it was easy. Use the meter switch to stop down the aperture and turn on the meter and adjust shutter/aperture to center the needle. Turn the switch off (aperture opens fully), focus and shoot as much as you wish until light or subject changes. Auto-aperture takes care of opening/closing the iris for each shot by flipping a "paddle" in the mirror box that engages the stop-down pin that protrudes from the back of the lens.

Open aperture metering, OTOH, allows metering with the lens wide open. This is accomplished by coupling the aperture ring to the body's meter mechanism. That coupling is the non-crippled part of the non-crippled K-mount and one of the distinguishing features of the S-M-C and SMC Takumar lenses. The Spotmatic F features manual open-aperture metering allowing the meter to remain active while actively shooting and for the user to adjust exposure if needed. As with the regular Spotmatic, aperture automation is handled by engaging the stop-down pin on the lens rear. Operation is similar to the KX, KM, and K1000.

Herein is where some of the confusion arises. S-M-C and SMC lenses have a second, very small pin on the lens mount face that has nothing to do with aperture automation, but does help support trouble-free open aperture metering. That pin allows the lens to detect when it is mated to an open-aperture meter body and engages a lock on the A/M switch. This sort of interlock prevents having the lens stopped down when doing open-aperture metering (the aperture ring coupling still being engaged).

As for the OP's ES II, it and the ES add aperture-priority exposure automation to the mix. In use, both models operate in a manner very similar to the K2, ME Super and numerous other Av/M capable cameras that use the the original K-mount lens.


Steve

Last edited by stevebrot; 05-23-2016 at 07:39 PM.
05-23-2016, 07:53 PM   #15
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QuoteOriginally posted by stevebrot Quote
Not a problem. All open-aperture meter cameras are auto-aperture, but not all auto-aperture cameras feature open-aperture metering.

I shot for 12 years with a stop-down meter camera (e.g. Spotmatic). Without automatic aperture, it would have been a pain. With auto-aperture, it was easy. Use the meter switch to stop down the aperture and turn on the meter and adjust shutter/aperture to center the needle. Turn the switch off (aperture opens fully), focus and shoot as much as you wish until light or subject changes. Auto-aperture takes care of opening/closing the iris for each shot by flipping a "paddle" in the mirror box that engages the stop-down pin that protrudes from the back of the lens.

Open aperture metering, OTOH, allows metering with the lens wide open. This is accomplished by coupling the aperture ring to the body's meter mechanism. That coupling is the non-crippled part of the non-crippled K-mount and one of the distinguishing features of the S-M-C and SMC Takumar lenses. The Spotmatic F features manual open-aperture metering allowing the meter to remain active while actively shooting and for the user to adjust exposure if needed. As with the regular Spotmatic, aperture automation is handled by engaging the stop-down pin on the lens rear. Operation is similar to the KX, KM, and K1000.

Herein is where some of the confusion arises. S-M-C and SMC lenses have a second, very small pin on the lens mount face that has nothing to do with aperture automation, but does help support trouble-free open aperture metering. That pin allows the lens to detect when it is mated to an open-aperture meter body and engages a lock on the A/M switch. This sort of interlock prevents having the lens stopped down when doing open-aperture metering (the aperture ring coupling still being engaged).

As for the OP's ES II, it and the ES add aperture-priority exposure automation to the mix. In use, both models operate in a manner very similar to the K2, ME Super and numerous other Av/M capable cameras that use the the original K-mount lens.


Steve
Yup. That sums it up pretty well. The interlock prevents exposure errors that will occur if an SMC lens is in M mode when on a full aperture metering body. If the lens is in A mode, stopping down using the meter/stop down switch will give correct exposure as well as DOF preview. Hopefully Pentax will make this simpler when they release the ESIII.
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