Pentax Spotmeter Calibration

Kilgallb · Aug 22, 2022

I own three Pentax spotmeters. One is a Spotmeter III the other two are type V.

I checked all three on the same spot. One reads 3, one reads 4 and the Spotmeter III READS 5 1/3.

So is there a way to calibrate these things?

DREW WILEY · Aug 22, 2022

The Hollywood outfit which did that for me is out of business, and I don't tolerate even 1/3 EV deviance in my meters one from another. Maybe somebody here has Richard Ritter's contact information, who still does that.

Sirius Glass · Aug 23, 2022

I too had all my light meters, except the Hasselblads which were done by Hasselblad, calibrated at Quality Light Metric before George retired. Now I have Samy's Camera send them out to the company they use since George retired. Call Samy's and have all three of yours calibrated at the same time, the same way by the same company.

RalphLambrecht · Aug 23, 2022

Kilgallb said:
I own three Pentax spotmeters. One is a Spotmeter III the other two are type V.

I checked all three on the same spot. One reads 3, one reads 4 and the Spotmeter III READS 5 1/3.

So is there a way to calibrate these things?

Kodak Gray Card in full sun should read EV 15 but it depends on the angle of the card a bit.(one edge pointing straight to the ground is best)

AgX · Aug 23, 2022

Can Pentax Spotmeters only be used with large format cameras?

Sirius Glass · Aug 23, 2022

AgX said:
Can Pentax Spotmeters only be used with large format cameras?

No I also use them for my Hasselblad. My Nikons have a spot meter mode built in so I do not use the Pentax for that.

madNbad · Aug 23, 2022

There’s an ad in the classified for a Pentax spot meter that had just been serviced by Richard Ritter. It has a receipt that shows his address as PO Box 401, Townshend, VT 05353.

eli griggs · Aug 23, 2022

madNbad said:
There’s an ad in the classified for a Pentax spot meter that had just been serviced by Richard Ritter. It has a receipt that shows his address as PO Box 401, Townshend, VT 05353.

Thanks

madNbad said:
There’s an ad in the classified for a Pentax spot meter that had just been serviced by Richard Ritter. It has a receipt that shows his address as PO Box 401, Townshend, VT 05353.

Thanks for posting this information.

By any chance is there a phone number that he can be reached at?

madNbad · Aug 23, 2022

Here’s a link to the ad. Send the OP a message and he could probably help you.

https://www.photrio.com/forum/threads/pentax-1-degree-digital-spotmeter-calibrated.193758/

Nitroplait · Aug 23, 2022

What do you need 3 for?
Having 3 old spotmeters is calling for trouble as they will inevitably vary from each other. Even when calibrated together, they will probably begin to drift apart soon.
I have one Spotmeter III. It is nice but I always think it is too heavy to take out in the field. I can't imagine anyone using more than one at a time.

BTW. What battery are you using in the III? I suppose you know that you can't use a modern 1.5V Alkaline or 1.55 Silver Oxide without voltage regulation to the 1.35V of the original mercury battery?
A modern battery will give a too high reading on the Normal scale (the Low scale should be correct as it is using the 9V cell).
I use a cheap zinc/air hearing aid battery in a dumb adapter to overcome this issue.

AgX · Aug 23, 2022

Nitroplait said:
What do you need 3 for?

Because of my rule-of-3?

One for use, one as immediate spare and one for parts at least.

Nitroplait · Aug 23, 2022

AgX said:
Because of my rule-of-3?

One for use, one as immediate spare and one for parts at least.

Then OP needs another Spotmeter V

David Lindquist · Aug 23, 2022

To paraphrase that old saw about watches, a man who has more than one light meter never knows how bright it is...

Though I suspect Drew has time pieces that are within femto-seconds of each other and with GMT...

(I think there's a more modern term that's replaced GMT but I forget what it is.)

David

Nitroplait · Aug 23, 2022

David Lindquist said:
To paraphrase that old saw about watches, a man who has more than one light meter never knows how bright it is...

Though I suspect Drew has time pieces that are within femto-seconds of each other and with GMT...

(I think there's a more modern term that's replaced GMT but I forget what it is.)

David

Same holds true for thermometers.

Sirius Glass · Aug 23, 2022

Nitroplait said:
What do you need 3 for?
Having 3 old spotmeters is calling for trouble as they will inevitably vary from each other. Even when calibrated together, they will probably begin to drift apart soon.
I have one Spotmeter III. It is nice but I always think it is too heavy to take out in the field. I can't imagine anyone using more than one at a time.

BTW. What battery are you using in the III? I suppose you know that you can't use a modern 1.5V Alkaline or 1.55 Silver Oxide without voltage regulation to the 1.35V of the original mercury battery?
A modern battery will give a too high reading on the Normal scale (the Low scale should be correct as it is using the 9V cell).
I use a cheap zinc/air hearing aid battery in a dumb adapter to overcome this issue.

Simple:

First for Zone 4.
Second for Zone 3.
Third for Zone 2.

Unless one is shooting slides. In that case use a similar assignment.

DREW WILEY · Aug 23, 2022

I use Pentax spotmeters for everything, even if the camera I have along happens to contain its own TTL metering system. It's more accurate. And there are quite formal standards for calibrating these so that NONE of them differ. Hollywood filmmakers depend on that fact. So do I, especially given the cost and fuss involved shooting color sheet film. Incidentially, I keep one away in storage unused, both as a potential spare someday, but mainly as a reference to check the others from time to time. Mine are all Pentax digital spotmeters (prior to "digital" becoming a dirty word), and seem to need a minor recalibration or internal cleaning about once a decade apiece. That statistic is improving, since I won't be around long enough to need calibration service much again. I have zero experience with older models of Pentax meters, so am not contradicting any warnings with respect to their repeatability.

So yeah, it is analogous to thermometers. And that's why Certified thermometers exist, which are based on even more expensive thermometers. Heck, up the hill at the LBL national lab they have thermometers accurate with millionths of a degree (bigger budget than you and me too). A basic Kodak Type III Process thermometer is all I need, and it's equivalent in accuracy to other certified scientific bulb thermometers in the $250 to $350 range. But no, I'm not the type to order a cheap turkey roasting thermometer from Amazon and repurpose it for the darkroom, simply because turkeys were routinely overcooked or undercooked due to its inaccuracy!

As far as watches go, I never wear one.

Sirius Glass · Aug 23, 2022

Sirius Glass said:
Simple:

First for Zone 4.

Second for Zone 3.

Third for Zone 2.

Unless one is shooting slides. In that case use a similar assignment.

DREW WILEY said:
I use Pentax spotmeters for everything, even if the camera I have along happens to contain its own TTL metering system. It's more accurate.

I agree, but I have been known to get lazy with 35mm because I am less likely to print more than a few any larger than 4"x6".

Roger Cole · Aug 23, 2022

A bit of an aside but it IS related to Pentax spot meters: is there any real consensus on whether the Zone VI conversion is worthwhile? I researched that some years back and wound up even more puzzled than before I started reading, with some saying it made a difference and others saying they couldn't detect any change at all.

I really need to replace my aging Soligor spot meter and relegate it to backup status. For my MF cameras I rely on my Lunapro SBC which is a great meter but even with the Vari-angle attachment which I have its narrowest angle is still 7.5 degrees, way too wide for good zone system work much of the time.

Sirius Glass · Aug 23, 2022

Roger Cole said:
A bit of an aside but it IS related to Pentax spot meters: is there any real consensus on whether the Zone VI conversion is worthwhile? I researched that some years back and wound up even more puzzled than before I started reading, with some saying it made a difference and others saying they couldn't detect any change at all.

I really need to replace my aging Soligor spot meter and relegate it to backup status. For my MF cameras I rely on my Lunapro SBC which is a great meter but even with the Vari-angle attachment which I have its narrowest angle is still 7.5 degrees, way too wide for good zone system work much of the time.

The Zone VI conversion is not a good way to go, I have been told by multiple people. There is a problem getting anyone to calibrate or recalibrate them.

DREW WILEY · Aug 23, 2022

There again, Richard Ritter is the expert because he made many of those conversions for Fred Picker. I have my doubts because not even all pan films have the same spectral sensitivity, and those were balanced for what Fred considered the logical choice of the era, ole Triassic X. And the balancing filters inside fade over time and need to be replaced; and Richard is probably the only person who can do that. Color-film-wise, I've heard certain Hollywood cinematographers praise em, and others curse em. But all of those modified meters are now getting old and potentially inaccurate.

A coated lens meter which precisely replicates the reading of the Pentax digital spotmeter is the Minolta F spotmeter. But I find the manual dial on the Pentax to be faster and a lot more intuitive than the pushbutton mode of the Minolta.

BrianShaw · Aug 23, 2022

David Lindquist said:
To paraphrase that old saw about watches, a man who has more than one light meter never knows how bright it is...

Though I suspect Drew has time pieces that are within femto-seconds of each other and with GMT...

(I think there's a more modern term that's replaced GMT but I forget what it is.)

David

UTC

Eric Rose · Aug 23, 2022

Isn't there an adjustment screw on them? I set mine to agree with my Nikon dslr on spot mode using a Kodak grey card or clear blue northern sky.

DREW WILEY · Aug 23, 2022

They need to be full-range calibrated using special equipment, not just center point balanced in reference to some alleged 18% gray card, and certainly not by means of blue sky, which itself can vary quite a bit. Otherwise, they wouldn't be reliable anywhere but at the middle, and then only under standardized artificial conditions. What use would that kind of meter be? The peak spectral sensitivity of the SPD is at green anyway, just like human vision.

Having a backup option like with your Nikon is nice; but you've got it backwards. You should be checking the Nikon meter performance using the Pentax meter, and not the other way around. But any significant difference between them should get you sleuthing for the reason why.

Stephen Benskin · Aug 23, 2022

Here are three papers on meter calibration:

An Interpretation of Current Exposure Meter Technology, Allen Stimson

Calibration Levels of Films and Exposure Devices, D. Connelly

Re-evaluation of Factors Affecting Manual or Automatic Control of Camera Exposure, James Scudder, C.N. Nelson, and Allen Stimson

These and more papers can be found at http://beefalobill.com/benskin/content

Kilgallb · Aug 24, 2022

Nitroplait said:
What do you need 3 for?
Having 3 old spotmeters is calling for trouble as they will inevitably vary from each other. Even when calibrated together, they will probably begin to drift apart soon.
I have one Spotmeter III. It is nice but I always think it is too heavy to take out in the field. I can't imagine anyone using more than one at a time.

BTW. What battery are you using in the III? I suppose you know that you can't use a modern 1.5V Alkaline or 1.55 Silver Oxide without voltage regulation to the 1.35V of the original mercury battery?
A modern battery will give a too high reading on the Normal scale (the Low scale should be correct as it is using the 9V cell).
I use a cheap zinc/air hearing aid battery in a dumb adapter to overcome this issue.

I have three meters because:

A guy on eBay had one on sale for parts. I got it for $15. It had a broken wire and works fine. It matches my K1000 exactly. It was rough and the light on the viewfinder does not work.

Before I found that gem I bought a Spotmeter V locally for $125

The spotmeter III was bought when the $125 meter failed. I managed to fix it later, much later.

Pentax Spotmeter Calibration

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