Lenses for Spotmatic F

Yesterday I bought a Spotmatic F in nice condition. As I already own an older Spotmatic and an SP500, I initially thought the meter switch was not working properly but after a last resort look at the manual, it appears to be o.k. as it is different from the original Spotmatic.

If I understand it correctly, with lenses designed for open aperture metering, the meter is on all the time and the switch at the side of the lens does not need to be operated and with lenses without the means to transmit aperture position to the body, the switch is pushed up to stop down the lens to meter in the same way as the older Spotmatic.

If I want to get some more lenses which are compatible with the open aperture metering of the F, what markings/designations do I need to look for? Are there any third party lenses which are compatible?


Steve.

I know the Super-Multi-Coated and SMC lenses have open aperture metering. There's a couple extra lugs on the back of the lens. I've never used an F tho, so my experience is limited.

Tamron made a Spotmatic F/ESII Adaptall mount I use one with my 17, 28 and 135mm Tamron lenses.

The later Pentax SMC Takumars have the F/ESII additional features but any other M42 lens can be used with sop down metering.

Ian

Steve,
As you say, the 'switch' is used for what are known as non-'SP-F cammed' lenses. Look on the rear of any 42mm lens you're considering. The SP-F cam is distinct from the aperture stop-down pin and rotates around the circumference of the lens rear element when you turn the aperture ring. The cam tells the camera body what lens aperture has been selected. As has already been said, lenses labelled 'SMC' or 'Super Multi Coated' have the cam, but there are some that have it but aren't labelled SMC, etc.. (I have a 55/f2 that is a straight Super Takumar but is cammed. I've read somewhere that Pentax used up their old stock of non-SMC optics in new-style lens bodies and knocked them out on lower range models). Some third party lenses and accessories (eg extension tubes) were made with the cam, but personally I'd spend a bit more and go for the real deal (if only for that silky smooth focussing action of Pentax lenses!)

The SP-F's meter being switched on whenever the lens cap's off has always been a great source of annoyance to me (as with the K1000), as someone who doesn't use a cap except when the lens is rolling round in the gadget bag. It's not just the fact of using up battery power unnecessarily, but also the fact that without the cap (and the meter therefore switched on), I dread to think what a shock it gives the system if the camera happens to be pointed inadvertently at the sun or some other bright source. In the never-ending discussion about replacements for the mercury batteries for which that era of Pentaxes were designed and whether the small extra voltage of a silver cell will affect the reading of SPs and SP2s, it does seem to be generally agreed that it doesn't matter a hoot with the SP-F as it has different meter circuitry (getting into the realms of balanced and unbalanced bridges.)

The SP-F does seem to be regarded as a bit of an anomaly in Pentax circles - even in Danilo Cecchi's book on Pentax 35mm SLRs, he's rather dismissive of it as a bit of a gap-filler between the stop down metering screw mount range and the open-aperture metering K bayonet mount range that shortly followed it, but lack of metering switch aside, I think it's a rather neat camera!

Happy lens hunting!
Steve

Steve Roberts said:

As has already been said, lenses labelled 'SMC' or 'Super Multi Coated' have the cam, but there are some that have it but aren't labelled SMC, etc.

Click to expand...

That's what I wanted to know. It's easy to spot the difference when you can actually see the rear but I didn't know what to look for in a description.

So if it's labelled SMC or Super Multi Coated and has an M42 mount then it should be compatible.

Steve Roberts said:

In the never-ending discussion about replacements for the mercury batteries for which that era of Pentaxes were designed and whether the small extra voltage of a silver cell will affect the reading of SPs and SP2s, it does seem to be generally agreed that it doesn't matter a hoot with the SP-F as it has different meter circuitry (getting into the realms of balanced and unbalanced bridges.).

Click to expand...

I'm certain that the Spotmatic F has the bridge circuit - but so have the earlier models. In my non F Spotmatic and my SP500, I use any 1.5 volt cell I can make fit and I have had perfectly exposed slides from both of them.


Steve.

Hello,
I want to add that the SMC Takumars which are suitable for measurement with open aperture have a very small pin on their rear side which prevents to switch the Auto/Manual lever on the lens from Auto to Manual if it looks out. Only if you push the pin in, you can move the lever. The flange of the camera body has a groove which prevents the pin from being pushed in. Older SP's don't have this groove. You can use the old meter-switch as a depth of field control. The SP F has definitely a bridge circuit too like the SP and SP II.

Steve Smith said:

I'm certain that the Spotmatic F has the bridge circuit - but so have the earlier models. In my non F Spotmatic and my SP500, I use any 1.5 volt cell I can make fit and I have had perfectly exposed slides from both of them.
Steve.

Click to expand...

There have been all kinds of myths, rumours and supposition on this subject, even down to an alleged difference between earlier and later Spots. Like you, I've never had any problem, though the extra 0.15v of a silver cell does make the meter needle swing rather further for a given f-stop change. By trimming a couple of internal resistor values it's possible to restore the meter to its original proportional action.

Steve

Two things you will immediately spot from a detailed photo of the back of the lens...

A very tiny pin with short travel. This functions to hold the Auto/Manual switch in Auto position - the lens switch is useful on older Spotmatics but disastrous (if you consider several stops overexposure disastrous) with the F and ES.

A square block.

Steve Roberts said:

though the extra 0.15v of a silver cell does make the meter needle swing rather further for a given f-stop change. By trimming a couple of internal resistor values it's possible to restore the meter to its original proportional action.

Click to expand...

As correct exposure is shown with zero current flowing through the meter, it will not make any difference to this. However, if you have remembered how far up or down you set the meter to over or under expose (similar to the f stop change swing you refer to) then this position will change slightly when changing from mercury to silver or alkaline.


Steve.

Steve Smith said:

As correct exposure is shown with zero current flowing through the meter, it will not make any difference to this. However, if you have remembered how far up or down you set the meter to over or under expose (similar to the f stop change swing you refer to) then this position will change slightly when changing from mercury to silver or alkaline.


Steve.

Click to expand...

Indeed - the indication of correct exposure is maintained, but the position of the needle above the centre for, say, +1 stop overexposure is in my experience considerable. The effect can be something of a nuisance when trying to put the needle bang in the middle as a minor change of aperture can send it swinging wildly upwards or downwards. The amount of swing doesn't actually matter if, like me you'd normally set it to dead centre then open or shut down a click, but trying to get the thing to centre in the first place often leaves me trying to set the aperture ring (unnecessarily) at some finicky point somewhere in between half stops. They do seem to differ between cameras, though. Don't tell the Environmental Police, but I do still also have two good PX400 mercury cells that I use from time !!!!
Steve

What a great thread! This past winter a friend gave me his father's Spotmatic F with three lenses.. one SMC 55mm 1.8, one Tamron with what appears to be a very early adaptall mount 35-80mm 2.8 zoom macro, (really nice macro!) and an Opticam Auto (?) 28mm 2.8. Between them, these three lenses cover just about every issue discussed above. If this thread had appeared four months earlier, I would have solved the mysteries of these lenses a lot easier than I eventually did.
By the way, in the short time I have had this camera, it has become my favourite 35mm camera. The SMC and Tamron are really good lenses, and from what I've seen, the Opticam is not too bad either.

Cheers,

Steve Smith said:

So if it's labelled SMC or Super Multi Coated and has an M42 mount then it should be compatible.

Click to expand...

I've seen (and owned) some Super-Multi-Coated Takumars that did not have the linkage. Also the front ring might have been changed (faked) by the current or a previous owner. If the aperture linkage is important for you then you should inspect the lens physically or at least ask for a sharp picture of the rear of the lens (cap off, of course).

For what its worth, I just went out with my Spotmatic F. I have 6 lenses from 21mm-200mm. Only two of them have the auto linkage. (50mm and 35mm) The other 3 do not. (Asanamua 21mm, super tak 28mm, super tak 105mm, and vivitar 200mm).

The wide angles did not bother me a bit using stop-down metering since I was aiming them at stationary subjects. The longer lenses were more of a pain. People kept going in and out of the shade. I just decided to shoot them only in the sun.

We will see how they turned out in a few weeks.