Spotmatic F with odd meter issues ...

Daire Quinlan · Oct 26, 2012

I just got a Spotmatic F that seems to be behaving a bit weirdly. Stick a super-takumar on the front (not smc) and the meter is reasonably accurate. However if I hit the stop down switch the meter immediately dives by about two stops, even if I haven't stopped down the lens. My understanding was that with the F there was no connection between the stop down switch and the meter electronics so I'm at a loss to understand how this is happening.

I have a couple of SPs as well so I understand the difference between the operation of the switch in the different models. Anyone any ideas ? I've got to disassemble it anyway to clean it up so I may poke around in the meter electronics at the same time.

PentaxBronica · Oct 26, 2012

I've not handled a Spotmatic F but I do have an original Spotty.

I always thought that when using the pre-SMC Takumars on the F (or ES or ES II) the stop-down switch worked just like that on the original - set lens to Auto, then when you push the switch it'll stop the lens down and turn the meter on?

I would suspect the film speed selector if your metering is wobbly, both my KM and K1000 (essentially the same mechanism) have problems there.

Ian Grant · Oct 26, 2012

I had a Spotmatic F back in the early 70's and I've had another for about 9 years.

The stop down switch must cut out the SMC full aperture metering system. I'd expect the meter to read incorrectly with a non SMC lens without the meter switch being used as there's no lug on the lens registering the aperture the lens is set to.

Ian

Hatchetman · Oct 26, 2012

I think(?) it may be working correctly. It was designed for an SMC lens, otherwise it works like the original Spotmatic, so when you hit the switch the meter turns off.

Bill Burk · Oct 26, 2012

It's possible that the meter is "off" until you push the Depth of Field Preview (Meter On) switch on the Spotmatic F.

I don't have any Takumar's (robbed long ago). But with no lens on my Spotmatic F, I get meter needle all the way to the top - the meter off state. When I move the "Aperture" slider in the body, the meter comes on and responds. This is expected "Always On" mode of the SMCT lens.

A Takumar or Super Takumar lens will not move the "Aperture" slider. The meter will not be on until you turn on the Depth of Field Preview switch.

Bill Burk · Oct 27, 2012

In other words, on a Super Takumar lens or Takumar lens, there is a connection with the meter switch and the meter electronics on a Spotmatic F. Soon as you put an SMCT lens on, the meter switch is disconnected and the meter is always on.

You don't have to disassemble the camera to discover this. Just take off the lens and slide the aperture cam (inside top of lens mount).

The meter is only accurate with Super Takumar or Takumar lenses when Depth of Field Preview switch is up. The meter is only accurate with SMCT lenses when Depth of Field Preview switch is down.

With Super Takumar or Takumar lenses, you can use the Manual / Auto slider on the base of the lens as you wish. With SMCT lenses a tiny pin enforces the fact that you must always keep this slider on Auto. If you override this tiny pin and leave the SMCT slider on Manual, you will double-compensate for aperture and the metering will be far-off. (How can this happen you ask? If you also shoot a regular Spotmatic and interchange lenses you might leave a lens on Manual - it's happened to me).

Ian Grant · Oct 27, 2012

Bill Burk said:
In other words, on a Super Takumar lens or Takumar lens, there is a connection with the meter switch and the meter electronics on a Spotmatic F. Soon as you put an SMCT lens on, the meter switch is disconnected and the meter is always on.

That's a bit confused :confused:

There's a lug on the SMC Takumar lens that turns the meter on, however it does not de-activate the stop down metering switch which if used then gives false readings. So just trying it with a correct reading of a 30th @f5.6 when the stop down switch is used it claim itneeds a 30th @ f11 (both with SMC Takumar lens).

I had great difficulty persuading my wife not to use the meter switch on her K mount Pentax with its standard lens, this gave similar false readings.

Ian

Bill Burk · Oct 27, 2012

Ian Grant said:
That's a bit confused :confused:

There's a lug on the SMC Takumar lens that turns the meter on, however it does not de-activate the stop down metering switch which if used then gives false readings. So just trying it with a correct reading of a 30th @f5.6 when the stop down switch is used it claim itneeds a 30th @ f11 (both with SMC Takumar lens).

I had great difficulty persuading my wife not to use the meter switch on her K mount Pentax with its standard lens, this gave similar false readings.

Ian

Haaa, You are right. With SMCT lens on Spotmatic F, the Depth of Field switch is electrically disconnected but not mechanically disconnected. You can push the switch up and the needle moves with changes - so you can be misled.

You bring up an important point: the metering is wrong with an SMCT lens on a Spotmatic F with the Depth of Field Preview switch up. I would say it stinks as a feature in this respect.

Trask · Oct 27, 2012

I have a Spotmatic, but prefer to put an M42 adapter on my Canon T90 and use my Pentax lenses that way. The best of both manufacturers.

PentaxBronica · Oct 27, 2012

The tiny pin to keep the SMC lenses on Auto on the Spotmatic F/ES/ES II is a very clever bit of engineering.

The lens mounts on these cameras have a groove for the pin to drop into. Mount the same lens on a Spotmatic or earlier Pentax M42 body and the lack of a groove causes the pin to be pressed in, so the lens works just like a Super Takumar.

Daire Quinlan · Oct 27, 2012

Ok, so confusion aside (and I'm definately getting a little more confused here, not less) there are a couple of points here I'd like to clarify.

With a super takumar lens mounted, and the DOF/meter switch in the 'down' position (ie, 'off' from the point of view of one of the older spotmatics) the meter on my F responds, and indicates what seems to be a roughly correct exposure. From what I'm reading above, this exposure reading should be disregarded, that the SP F will meter correctly with super takumar lenses ONLY if the metering switch is slid up. That this reading (When I switch up the meter) is about 2 stops too slow is certainly an issue, but needs to be considered in isolation. I've got 1.5v silver oxide cells in it, roughly 80% of the internet seems to think this is fine because of the SP f's bridge circuit, and there's a vocal minority that claim that this view is mistaken.

I actually have an SMC 28mm that I can grab tomorrow so I can check the flipside of the coin, open aperture metering with the right lens.

I've -also- discovered to my annoyance that one speed is flaky, or rather one EV, ie 1/250 at 400iso or 1/60 at 100iso. This is the same as another of my older spotmatics, and I bet it's the same cause as well. Dunno if you've ever dis assembled a spotmatic, but the shutter speed selecter linkage to the metering circuit is two thin copper discs with a small contact between them. Both cameras sat around for years before I got them, I'd say there's a tiny spot of corrosion in the spot that little contact was sitting all those years or something. Hopefully lots of actioning it might clear it up a bit.

summicron1 · Oct 27, 2012

have you considered just skipping the batteries in the thing and buying a handheld meter? The circuitry in these cameras is edging up to 40 years of age, the sort of batteries they were made for are no longer made, a handheld meter, coupled to a knowledgable brain, will be far more accurate. I find it so with my M4 and so on.

Bill Burk · Oct 27, 2012

Daire Quinlan said:
Ok, so confusion aside (and I'm definately getting a little more confused here, not less) there are a couple of points here I'd like to clarify.

With a super takumar lens mounted, and the DOF/meter switch in the 'down' position (ie, 'off' from the point of view of one of the older spotmatics) the meter on my F responds, and indicates what seems to be a roughly correct exposure.

Certainly have heard enough variation to believe there are different "versions" of the Spotmatic F. Mine is the "Needle is Up when Meter is Off" variant. Heard there is a version where the needle is centered - surely something they fixed, makes me think mine's a late model (Honeywell).

Ricardo Miranda · Oct 27, 2012

Right! This is the way the Spotmatic F works. Well, at least mine and that's what it says on Manual.
The switch on the left is no longer a meter on/off but it only switches between full aperture metering when down to stop-down metering when up.
The meter is a "always on" type and only switches off with a lens cap or when light falls behind a certain level.
To use SMC lenses, the switch needs to be down. With Super Takumar and other earlier lenses, the switches goes up to stop down the lens to actual aperture.
Hope this helps!

Mine is the "Needle is Up when Meter is Off" variant. Heard there is a version where the needle is centered - surely something they fixed, makes me think mine's a late model (Honeywell).

That is only applicable to the earlier 1964 Pentax Spotmatic model that had a long history of small improvements.

Bill Burk · Oct 27, 2012

Ricardo Miranda said:
That is only applicable to the earlier 1964 Pentax Spotmatic model that had a long history of small improvements.

I have this Honeywell Spotmatic F in front of me now, and that's how it behaves.

Ian Grant · Oct 28, 2012

I've had early and late Spotmatic F's and when off the needle's been at the top, however that may vary depending on the ISO & shutter speed/aperture the camera's set to.

Batteries aren't a problem as there's a modern one that works fine, I bought two on Thursday.

Ian

Ricardo Miranda · Oct 28, 2012

Please see what the manual says: http://www.cameramanuals.org/pentax_pdf/pentax_spotmatic_f.pdf
On page 1 there is a description on how the meter switches on by removal of the lens cap. Also on pages 20 and 21 there is a description of the "stop-down lever" as Pentax calls it.
If the needle is up, regardless of the state of the stop-down lever, the meter is active.

Bill Burk · Oct 28, 2012

Hi Ricardo Miranda,

You are right on the point I asserted incorrectly. I said Needle is up when meter off. That's False

With no battery, my needle is centered.

I can simulate a Takumar or Super Takumar lens by unscrewing the SMCT lens one turn. Now I believe the linkage is designed to shoot the needle to top when "Depth of Field switch is Down" as a feature to keep user from thinking exposure is correct. When I cover the lens completely the needle returns to center as the meter "powers off" and I can watch it shoot to top when I let in a small amount of light.

Bill Burk · Oct 28, 2012

p.s. Does anyone have a spare "rewind knob" for Spotmatic F? I lost it once then I hunted it down and found it. I didn't put Loctite on it so it fell off again and I didn't notice before the street sweeper came by...

Ian Grant · Oct 28, 2012

I can probably get you one in early December, there's usually a stall at the camera fair I go to which has parts cameras for £1 ($1.55) and postage of a rewind crank would be very low. I bought an SIa for parts but had it working perfectly within 20mins, so had to buy another a few months later but the rewind was missing, The cranks are identical.

Ian

Bill Burk · Oct 28, 2012

Ian Grant said:
I can probably get you one in early December, there's usually a stall at the camera fair I go to which has parts cameras for £1 ($1.55) and postage of a rewind crank would be very low. I bought an SIa for parts but had it working perfectly within 20mins, so had to buy another a few months later but the rewind was missing, The cranks are identical.

Ian

If you see one, great!... I've done the same, bought a parts Spotmatic for the rewind knob and it was mint under patina. Ended up taking the rewind knob and putting a knob from a Canonet on it and gave it to a work acquaintence (I wasn't totally evil, I gave it away with an SMCT 35mm f/2 and Soligor Spot Sensor).

Ricardo Miranda · Oct 28, 2012

Bill,
Thank you! Incidentally, the Pentax K1000 is the only other Pentax with the same type of "light switch" as I call it. The stop-down lever should be the same as the ES and ES II models.
Many people got confused with that lever, including me when I first got one. I was used to the SP and SP II and had a couple of rolls badly exposed because I was flicking the switch up whit the SMCT lenses. Didn't read the manual until it was too late!

RichardH · Oct 28, 2012

Bill Burk said:
p.s. Does anyone have a spare "rewind knob" for Spotmatic F? I lost it once then I hunted it down and found it. I didn't put Loctite on it so it fell off again and I didn't notice before the street sweeper came by...

Bill, I sent you a pm.

Richard

Bill Burk · Oct 28, 2012

RichardH said:
Bill, I sent you a pm.

Richard

Thanks Richard,

Ian, enjoy the show but Richard is going to get me a rewind crank. I'm using Loctite this time. Got the bottle of Threadlocker 242 blue out already...

Ian Grant · Oct 28, 2012

Bill Burk said:
Ian, enjoy the show but Richard is going to get me a rewind crank. I'm using Loctite this time. Got the bottle of Threadlocker 242 blue out already...

Saves me having a wasted Pentax carcus It's this kind of kind of help that makes APUG such a great site.

Ian

Spotmatic F with odd meter issues ...

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