My new Pentax Spotmatic F (SPF)

dantonvb · 10-05-2019, 07:44 AM

I received yesterday my new SPF, with SMC-Takumar 50/1.4, near mint condition, with operating meter.
Using a SR 44 battery (1.5 volts) I compared the mettering with my K-5ii in center weighted mode:
SPF: f8 and 1/125s (iso 100)
K-5ii: f8 and 1/500s (iso 100)

Difference of two stops.

Do you think that the SPF meter is defective?

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**boriscleto** · 10-05-2019, 08:08 AM

No. The SP F used a 1.35v Mercury battery. It does not have a bridging circuit.

There are several solutions, Wein cell batteries, a simple adapter for PX75 hearing aid batteries, a battery adapter that lowers the voltage etc.

**tonyzoc** · 10-05-2019, 08:34 AM

Originally posted by dantonvb

I received yesterday my new SPF, with SMC-Takumar 50/1.4, near mint condition, with operating meter.

Using a SR 44 battery (1.5 volts) I compared the mettering with my K-5ii in center weighted mode:

SPF: f8 and 1/125s (iso 100)

K-5ii: f8 and 1/500s (iso 100)

Difference of two stops.

Do you think that the SPF meter is defective?

I've got an SPF and I get similar numbers with the SR44. The camera circuitry is supposed to knock the voltage down but doesn't seem to. I used an adapter with the 1.55v batteries and it gets closer but not perfect. I usually shoot B&W so I use the meter, under expose a little, use the sunny 16 rule...negatives come out fine. Unless you're shooting Ektachrome, you should be fine.

**MossyRocks** · 10-05-2019, 08:58 AM

My understanding is that it is a balanced meter so the voltage doesn't matter much so long as there is enough to run the meter. I've been using 1.5v 625 batteries in mine for the last 20 years without issue.

wings · 10-05-2019, 11:18 AM

That looks like new. Congratulations.

**boriscleto** · 10-05-2019, 12:17 PM

Originally posted by tonyzoc

I've got an SPF and I get similar numbers with the SR44. The camera circuitry is supposed to knock the voltage down but doesn't seem to. I used an adapter with the 1.55v batteries and it gets closer but not perfect. I usually shoot B&W so I use the meter, under expose a little, use the sunny 16 rule...negatives come out fine. Unless you're shooting Ektachrome, you should be fine.

Originally posted by MossyRocks

My understanding is that it is a balanced meter so the voltage doesn't matter much so long as there is enough to run the meter. I've been using 1.5v 625 batteries in mine for the last 20 years without issue.

The original Spotmatic, and the SP II, were not voltage dependent. The SP F is.

**ChrisPlatt** · 10-05-2019, 02:27 PM

aohc.it website states:

According to information from Gene Poon from Spotmatic discussion group such 1.35V voltage cells can be replaced in the Spotmatic series cameras with any matching 1.5V battery (silver oxide type are good). That's because original SP, SPII, SPIIa, SP500, SP1000 all use a bridge circuit where the meter measures the balance between the two legs of the bridge. Both legs of the bridge would be equally affected by any "normal" voltage variations. SPF uses a dual coil meter, the two halves equally affected by any voltage variations.

pentaxuser.uk states:

SP F.
• Mallory PX625, Duracell PX625A, Excel Z625PX, Eveready E-625N.
• The Spotmatic F uses a dual coil meter movement that, like the bridge circuit, cancels out battery voltage variations on the level we are dealing with here. So it is immune to the difference between 1.35v and 1.5v, too. The original battery for the Spot F was a mercury type. In this case, Pentax used the identical circuit in the KM and K1000, without any electronic changes. They substituted the silver types with NO ALTERATION at all.

My SP-F had been serviced by Eric Hendrickson before I ever used it. He is the person I'd trust to know best whether adjustment is normally required.

Chris

Last edited by ChrisPlatt; 10-05-2019 at 02:35 PM.

**beachgardener** · 10-05-2019, 02:32 PM

That is a very nice looking spotty

and thank you all for the battery information.

here is mine

stevebrot · 10-05-2019, 03:08 PM

Originally posted by dantonvb

SPF: f8 and 1/125s (iso 100)
K-5ii: f8 and 1/500s (iso 100)

Difference of two stops.

Are you using the same lens on both cameras? If so, it is likely that the K-5II reading is the larger part of the problem. Do the comparison with the K-5II attached to a lens where the camera is able to control the aperture. Stop-down metering on the K-5II is not bad, but also not reliable.

Secondly, did you remember that the SP F does not require diaphragm stop-down to meter when used with an SMC Takumar lens? The meter switch should be in the OFF (down) position and the A/M switch in the A (auto) position such that your SMC lens is wide open to meter.

There is also the chance that the coupling mechanism on the body, particularly alignment of the tab for lens orientation that engages the boss on the lens rear, is not proper.

It is also possible that the SP F's meter simply needs adjustment.

I hope this helps.

Steve

stevebrot · 10-05-2019, 03:12 PM

Originally posted by ChrisPlatt

aohc.it website states:

According to information from Gene Poon from Spotmatic discussion group such 1.35V voltage cells can be replaced in the Spotmatic series cameras with any matching 1.5V battery (silver oxide type are good). That's because original SP, SPII, SPIIa, SP500, SP1000 all use a bridge circuit where the meter measures the balance between the two legs of the bridge. Both legs of the bridge would be equally affected by any "normal" voltage variations. SPF uses a dual coil meter, the two halves equally affected by any voltage variations.

pentaxuser.uk states:

SP F.
• Mallory PX625, Duracell PX625A, Excel Z625PX, Eveready E-625N.
• The Spotmatic F uses a dual coil meter movement that, like the bridge circuit, cancels out battery voltage variations on the level we are dealing with here. So it is immune to the difference between 1.35v and 1.5v, too. The original battery for the Spot F was a mercury type. In this case, Pentax used the identical circuit in the KM and K1000, without any electronic changes. They substituted the silver types with NO ALTERATION at all.

My SP-F had been serviced by Eric Hendrickson before I ever used it. He is the person I'd trust to know best whether adjustment is normally required.

Chris

Thanks for adding this to the discussion. My experience is that the SP F is not voltage dependent.* The circuit diagram also indicates such. That being said, I do use an MR-9 adapter for convenience, if nothing else. My SP F meter agrees well with my K-3 both for open-aperture and stop-down aperture measurements. If one is uncertain regarding voltage, the MR-9 adapter + SR43 cell is a very workable and cost-effective solution.

Kanto Camera (Japan) | MR-9 (voltage stepdown)

Steve

(...no relation to Kanto Camera except as a satisfied customer...)

* I have three cameras that take the PX625 that do not have a bridging circuit and the difference is obvious with and without proper voltage.

Komainu · 10-07-2019, 07:15 PM

First of all congrats on that good looking camera.

I recently got another SPF which is currently being serviced by Hasegawa repair.
Just to add on the battery discussion, he did test the meter using a regular 1.5v cell and a rubber band. I believe the battery should be fine, so the meter might need an adjustment if you cant discard other reasons.

10-05-2019, 03:08 PM	#9
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by dantonvb SPF: f8 and 1/125s (iso 100) K-5ii: f8 and 1/500s (iso 100) Difference of two stops. Are you using the same lens on both cameras? If so, it is likely that the K-5II reading is the larger part of the problem. Do the comparison with the K-5II attached to a lens where the camera is able to control the aperture. Stop-down metering on the K-5II is not bad, but also not reliable. Secondly, did you remember that the SP F does not require diaphragm stop-down to meter when used with an SMC Takumar lens? The meter switch should be in the OFF (down) position and the A/M switch in the A (auto) position such that your SMC lens is wide open to meter. There is also the chance that the coupling mechanism on the body, particularly alignment of the tab for lens orientation that engages the boss on the lens rear, is not proper. It is also possible that the SP F's meter simply needs adjustment. I hope this helps. Steve Last edited by stevebrot; 10-05-2019 at 03:29 PM.

10-05-2019, 03:12 PM	#10
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by ChrisPlatt aohc.it website states: According to information from Gene Poon from Spotmatic discussion group such 1.35V voltage cells can be replaced in the Spotmatic series cameras with any matching 1.5V battery (silver oxide type are good). That's because original SP, SPII, SPIIa, SP500, SP1000 all use a bridge circuit where the meter measures the balance between the two legs of the bridge. Both legs of the bridge would be equally affected by any "normal" voltage variations. SPF uses a dual coil meter, the two halves equally affected by any voltage variations. pentaxuser.uk states: SP F. • Mallory PX625, Duracell PX625A, Excel Z625PX, Eveready E-625N. • The Spotmatic F uses a dual coil meter movement that, like the bridge circuit, cancels out battery voltage variations on the level we are dealing with here. So it is immune to the difference between 1.35v and 1.5v, too. The original battery for the Spot F was a mercury type. In this case, Pentax used the identical circuit in the KM and K1000, without any electronic changes. They substituted the silver types with NO ALTERATION at all. My SP-F had been serviced by Eric Hendrickson before I ever used it. He is the person I'd trust to know best whether adjustment is normally required. Chris Thanks for adding this to the discussion. My experience is that the SP F is not voltage dependent.* The circuit diagram also indicates such. That being said, I do use an MR-9 adapter for convenience, if nothing else. My SP F meter agrees well with my K-3 both for open-aperture and stop-down aperture measurements. If one is uncertain regarding voltage, the MR-9 adapter + SR43 cell is a very workable and cost-effective solution. Kanto Camera (Japan) \| MR-9 (voltage stepdown) Steve (...no relation to Kanto Camera except as a satisfied customer...) * I have three cameras that take the PX625 that do not have a bridging circuit and the difference is obvious with and without proper voltage. Last edited by stevebrot; 10-05-2019 at 03:24 PM.

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10-05-2019, 08:08 AM	#2
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	No. The SP F used a 1.35v Mercury battery. It does not have a bridging circuit. There are several solutions, Wein cell batteries, a simple adapter for PX75 hearing aid batteries, a battery adapter that lowers the voltage etc.

10-05-2019, 08:34 AM	#3
tonyzoc Loyal Site Supporter Join Date: Jul 2018 Posts: 992	Originally posted by dantonvb I received yesterday my new SPF, with SMC-Takumar 50/1.4, near mint condition, with operating meter. Using a SR 44 battery (1.5 volts) I compared the mettering with my K-5ii in center weighted mode: SPF: f8 and 1/125s (iso 100) K-5ii: f8 and 1/500s (iso 100) Difference of two stops. Do you think that the SPF meter is defective? I've got an SPF and I get similar numbers with the SR44. The camera circuitry is supposed to knock the voltage down but doesn't seem to. I used an adapter with the 1.55v batteries and it gets closer but not perfect. I usually shoot B&W so I use the meter, under expose a little, use the sunny 16 rule...negatives come out fine. Unless you're shooting Ektachrome, you should be fine.

10-05-2019, 08:58 AM	#4
MossyRocks Loyal Site Supporter Join Date: Nov 2017 Location: Minnesota Photos: Gallery \| Albums Posts: 2,982	My understanding is that it is a balanced meter so the voltage doesn't matter much so long as there is enough to run the meter. I've been using 1.5v 625 batteries in mine for the last 20 years without issue.

10-05-2019, 11:18 AM	#5
wings Senior Member Join Date: May 2017 Posts: 209	That looks like new. Congratulations.

10-05-2019, 12:17 PM	#6
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	Originally posted by tonyzoc I've got an SPF and I get similar numbers with the SR44. The camera circuitry is supposed to knock the voltage down but doesn't seem to. I used an adapter with the 1.55v batteries and it gets closer but not perfect. I usually shoot B&W so I use the meter, under expose a little, use the sunny 16 rule...negatives come out fine. Unless you're shooting Ektachrome, you should be fine. Originally posted by MossyRocks My understanding is that it is a balanced meter so the voltage doesn't matter much so long as there is enough to run the meter. I've been using 1.5v 625 batteries in mine for the last 20 years without issue. The original Spotmatic, and the SP II, were not voltage dependent. The SP F is.

10-05-2019, 02:27 PM	#7
ChrisPlatt Site Supporter Join Date: Nov 2007 Location: Rockaway Beach NYC Posts: 7,694	aohc.it website states: According to information from Gene Poon from Spotmatic discussion group such 1.35V voltage cells can be replaced in the Spotmatic series cameras with any matching 1.5V battery (silver oxide type are good). That's because original SP, SPII, SPIIa, SP500, SP1000 all use a bridge circuit where the meter measures the balance between the two legs of the bridge. Both legs of the bridge would be equally affected by any "normal" voltage variations. SPF uses a dual coil meter, the two halves equally affected by any voltage variations. pentaxuser.uk states: SP F. • Mallory PX625, Duracell PX625A, Excel Z625PX, Eveready E-625N. • The Spotmatic F uses a dual coil meter movement that, like the bridge circuit, cancels out battery voltage variations on the level we are dealing with here. So it is immune to the difference between 1.35v and 1.5v, too. The original battery for the Spot F was a mercury type. In this case, Pentax used the identical circuit in the KM and K1000, without any electronic changes. They substituted the silver types with NO ALTERATION at all. My SP-F had been serviced by Eric Hendrickson before I ever used it. He is the person I'd trust to know best whether adjustment is normally required. Chris Last edited by ChrisPlatt; 10-05-2019 at 02:35 PM.

10-05-2019, 02:32 PM	#8
beachgardener Site Supporter Join Date: Sep 2013 Location: Australia Photos: Gallery Posts: 3,842	That is a very nice looking spotty and thank you all for the battery information. here is mine

10-07-2019, 07:15 PM	#11
Komainu New Member Join Date: Oct 2019 Location: Tokyo Posts: 21	First of all congrats on that good looking camera. I recently got another SPF which is currently being serviced by Hasegawa repair. Just to add on the battery discussion, he did test the meter using a regular 1.5v cell and a rubber band. I believe the battery should be fine, so the meter might need an adjustment if you cant discard other reasons.