Spotmatic F metering puzzle

JimboWalker · 05-03-2020, 07:18 AM

When metering at open aperture (Auto) my reading is off my 2 stops, but when I meter in stop down mode, the reading is accurate. I am using smc lenses and they seem to couple well with the body. What is going on here? Thanks!

stevebrot · 05-03-2020, 11:00 AM

Originally posted by JimboWalker

I am using smc lenses and they seem to couple well with the body. What is going on here?

Don't use stop-down metering with SMC/S-M-C lenses. (See SP F manual page 20, 21)

If you feel that open aperture metering is off, the cause may be an issue with coupling mechanism or adjustment of the open aperture metering circuit.

Steve

JimboWalker · 05-03-2020, 05:51 PM

Originally posted by stevebrot

Don't use stop-down metering with SMC/S-M-C lenses. (See SP F manual page 20, 21)

If you feel that open aperture metering is off, the cause may be an issue with coupling mechanism or adjustment of the open aperture metering circuit.

Steve

Thanks! I will check the manual. I presume that stop down metering should be accurate with my Russian Helios lenses. I need to check against my handheld meters. I do not think my batteries are suspect. I have tried every battery combo out there and the meter responds the same.

stevebrot · 05-03-2020, 09:50 PM

Originally posted by JimboWalker

Thanks! I will check the manual. I presume that stop down metering should be accurate with my Russian Helios lenses. I need to check against my handheld meters. I do not think my batteries are suspect. I have tried every battery combo out there and the meter responds the same.

IMPORTANT: You should be aware of an additional complication...sorry

The Spotmatic F, ES, and ESII along with the Electrospotmatic have poor compatibility with non-Asahi (Takumar) lenses such that Pentax limited the documented compatibility to their product. Use of other brand lenses is done at the risk of damage to the camera and lens. Details are at the thread linked below:

Spotmatic F, ES, ESII | Third-party Lens Compatibility - PentaxForums.com

Some of my non-Pentax M42 lenses mount cleanly, but the rest do not.

Steve

Last edited by stevebrot; 05-03-2020 at 10:00 PM.

**Lowell Goudge** · 05-04-2020, 03:28 PM

As I recall, there is a small pin that is used to provide positive location of the lenses that can use wide open aperture metering. Are you sure it is engaged in the body. The aperture coupling is only 50% of the issue. Since the op says the coupling is engaged I wonder if the pin is locked in place

05-03-2020, 07:18 AM	#1
JimboWalker Forum Member Join Date: Aug 2018 Posts: 52	Spotmatic F metering puzzle When metering at open aperture (Auto) my reading is off my 2 stops, but when I meter in stop down mode, the reading is accurate. I am using smc lenses and they seem to couple well with the body. What is going on here? Thanks!

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05-03-2020, 11:00 AM	#2
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by JimboWalker I am using smc lenses and they seem to couple well with the body. What is going on here? Don't use stop-down metering with SMC/S-M-C lenses. (See SP F manual page 20, 21) If you feel that open aperture metering is off, the cause may be an issue with coupling mechanism or adjustment of the open aperture metering circuit. Steve

05-03-2020, 05:51 PM	#3
JimboWalker Forum Member Join Date: Aug 2018 Posts: 52 Original Poster	Originally posted by stevebrot Don't use stop-down metering with SMC/S-M-C lenses. (See SP F manual page 20, 21) If you feel that open aperture metering is off, the cause may be an issue with coupling mechanism or adjustment of the open aperture metering circuit. Steve Thanks! I will check the manual. I presume that stop down metering should be accurate with my Russian Helios lenses. I need to check against my handheld meters. I do not think my batteries are suspect. I have tried every battery combo out there and the meter responds the same.

05-03-2020, 09:50 PM	#4
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by JimboWalker Thanks! I will check the manual. I presume that stop down metering should be accurate with my Russian Helios lenses. I need to check against my handheld meters. I do not think my batteries are suspect. I have tried every battery combo out there and the meter responds the same. IMPORTANT: You should be aware of an additional complication...sorry The Spotmatic F, ES, and ESII along with the Electrospotmatic have poor compatibility with non-Asahi (Takumar) lenses such that Pentax limited the documented compatibility to their product. Use of other brand lenses is done at the risk of damage to the camera and lens. Details are at the thread linked below: Spotmatic F, ES, ESII \| Third-party Lens Compatibility - PentaxForums.com Some of my non-Pentax M42 lenses mount cleanly, but the rest do not. Steve Last edited by stevebrot; 05-03-2020 at 10:00 PM.

05-04-2020, 03:28 PM	#5
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,888	As I recall, there is a small pin that is used to provide positive location of the lenses that can use wide open aperture metering. Are you sure it is engaged in the body. The aperture coupling is only 50% of the issue. Since the op says the coupling is engaged I wonder if the pin is locked in place