[VincentK]

When you put in a 1,5Volt battery does the needle show that the lighting is more lit or darker than it really is?

[Bengan]

Don't overthink things. The 1,55V 387S will work just fine I've used it and other 1,55V batteries for some time (other sizes without the plastic spacer are somewhat difficult to get in place but once you do, they work)

[pickles]

I have also used the 1.55V batteries with no exposure issues at all.
Pickles.

[mbphoto]

Sorry, some errors in my previous post.. The spotmatic UNDERexposes (1/1000s vs 1/320s on the Nikon)..

Here's a corrected version:
Hi

Wanted to chime in, since I only just got my Spotmatic SP and replaced the mercury battery inside (no corrosion, lucky me!).

After reading countless affirmations that the 1.5 V Silver Oxide batteries would work as well, I ordered a pack of Varta V394 batteries to test it myself.
(The mercury battery was in a tiny blue plastic ring that held it snug in place inside the battery compartment, and the V394 (aka SR936SW) fits this plastic ring just as well.)

The V394 is the perfect shape and at roughly 2 USD per cell (Varta, not a chinese knock-off), the price is alright.

So, installed the battery, switched on the meter, and the needle moves. Awesome!

Went outside, pointed the lens (a Super-Multi-Coated Takumar 35mm f/3.5) at something homogeneously lit (e.g. the blue sky away from the sun, the green grass, etc.) and played around with the settings.
The meter seems to work fine: reducing shutter speed by 1 stop, I need to open the aperture by 1 stop to get it centered again. So far, so good.


Now, let's compare it to a digital meter..
Took my Nikon D810 (which has a nice meter that I trust) and used the 50/1.8 (don't have a 35 yet) to take the same readings..
Unfortunately, the Nikon had the exposure time by >1 full stop longer than the Spotmatic. (both lenses metered at f/5.6)

I then used my Fuji X-T10 and compared again. Sure, the Fuji has a slightly different approach to ASA values, but it too chose significantly longer exposure times than the Pentax.


Conclusion:
While the batteries DO in fact work, the camera will underexpose by a little over a full stop!

You can, obviously, set the ASA to 100 when using 200 ASA film (or 200 for 400 ASA film) to increase the exposure time.

Sure, film such as Portra 400 shouldn't suffer from underexposure, but I came to like the film overexposed during exposure and pulled when scanning.. Gives it a more film-ish look.


How do you handle the underexposure?

And don't tell me that my cameras are wrong.. Even my Canon 1Ds III tells me that the Spotmatic is exposing wrongly

[timw4mail]

Sorry, some errors in my previous post.. The spotmatic UNDERexposes (1/1000s vs 1/320s on the Nikon)..

Here's a corrected version:
Hi

Wanted to chime in, since I only just got my Spotmatic SP and replaced the mercury battery inside (no corrosion, lucky me!).

After reading countless affirmations that the 1.5 V Silver Oxide batteries would work as well, I ordered a pack of Varta V394 batteries to test it myself.
(The mercury battery was in a tiny blue plastic ring that held it snug in place inside the battery compartment, and the V394 (aka SR936SW) fits this plastic ring just as well.)

The V394 is the perfect shape and at roughly 2 USD per cell (Varta, not a chinese knock-off), the price is alright.

So, installed the battery, switched on the meter, and the needle moves. Awesome!

Went outside, pointed the lens (a Super-Multi-Coated Takumar 35mm f/3.5) at something homogeneously lit (e.g. the blue sky away from the sun, the green grass, etc.) and played around with the settings.
The meter seems to work fine: reducing shutter speed by 1 stop, I need to open the aperture by 1 stop to get it centered again. So far, so good.


Now, let's compare it to a digital meter..
Took my Nikon D810 (which has a nice meter that I trust) and used the 50/1.8 (don't have a 35 yet) to take the same readings..
Unfortunately, the Nikon had the exposure time by >1 full stop longer than the Spotmatic. (both lenses metered at f/5.6)

I then used my Fuji X-T10 and compared again. Sure, the Fuji has a slightly different approach to ASA values, but it too chose significantly longer exposure times than the Pentax.


Conclusion:
While the batteries DO in fact work, the camera will underexpose by a little over a full stop!

You can, obviously, set the ASA to 100 when using 200 ASA film (or 200 for 400 ASA film) to increase the exposure time.

Sure, film such as Portra 400 shouldn't suffer from underexposure, but I came to like the film overexposed during exposure and pulled when scanning.. Gives it a more film-ish look.


How do you handle the underexposure?

And don't tell me that my cameras are wrong.. Even my Canon 1Ds III tells me that the Spotmatic is exposing wrongly

How much the underexposure matters depends largely on the film. B&W film will have the least issue, reversal/slide film will have the most.

[John Poirier]

Today I decided to confirm some tests I did a number of years ago. I don't completely trust comparisons with digital camera meters. My chief concerns are that digital camera ISO ratings can be fudged, and that "matrix" metering can behave differently from the metering pattern of old film cameras. As well, testing methodology affects results. Metering off an 18% gray card, which is considered a standard method for testing meters, will produce different results from metering off a random subject.

I used a Sekonic L-358 incident meter, in incident mode, and a Pentax Spotmeter V. With a gray card used for the spot meter, the two meters agree within about .1 stop.

I tested a Spotmatic, Spotmatic 1000, and a Spotmatic II. I used the same fresh 394 battery in all three. My results with the various Spotmatics reading off a gray card were within .1 to .3 stops of the readings from the hand-held meters. All three cameras would have produced slight overexposure.

My results were consistent with my testing from years ago. At that time I tested three different types of silver oxide batteries and observed no differences in their behaviour.

Over the years my results on film from Spotmatics have been consistent with what the meters tell me.

I used to do large format process control involving hand-held meters and densitometers, so I am pretty confident in my procedures.

|What it boils down to is that, speaking for myself, I would not hesitate to use silver oxide batteries as a replacement for mercury batteries in Spotmatic bodies. I would not worry about recalibration or use of special adapters such as CRIS.

Cheers

[mbphoto]

Really interesting. Sure, the digital camera may be off, but I always use my Fuji to meter for the Yashica A..

If the Fuji were indeed telling me to overexpose by a full stop.. Shouldn't I see that in the results?

I'll do some tests with a cheap roll of Kodak film (not my beloved portra) and shoot some brackets 1 stop under, normal, and over exposed.

Thanks for your testing, though.

[John Poirier]

Really interesting. Sure, the digital camera may be off, but I always use my Fuji to meter for the Yashica A..

If the Fuji were indeed telling me to overexpose by a full stop.. Shouldn't I see that in the results?

I'll do some tests with a cheap roll of Kodak film (not my beloved portra) and shoot some brackets 1 stop under, normal, and over exposed.

Thanks for your testing, though.

You're welcome

Using a digital camera meter would very likely get you into the right ballpark, but may well be off in purist terms. In other words, your cameras may be wrong.

There is a Wikipedia article that contains a paragraph illustrating why I am skeptical about using digital cameras for metering film. I quote it below:

"Despite these detailed standard definitions, cameras typically do not clearly indicate whether the user "ISO" setting refers to the noise-based speed, saturation-based speed, or the specified output sensitivity, or even some made-up number for marketing purposes. Because the 1998 version of ISO 12232 did not permit measurement of camera output that had lossy compression, it was not possible to correctly apply any of those measurements to cameras that did not produce sRGB files in an uncompressed format such as TIFF. Following the publication of CIPA DC-004 in 2006, Japanese manufacturers of digital still cameras are required to specify whether a sensitivity rating is REI or SOS.[citation needed] "

Link to the full article, which discusses both film speed and digital camera ISO measurement:

Film speed - Wikipedia

Colour negative film has quite a bit of latitude, especially for overexposure. In other words, you won't necessarily see the difference between a correctly exposed neg and an overexposed one unless you have a totally exposure locked printing process, or a densitometer, or are quite experienced in "reading" negatives.

In the real world there are variables such as shutter speed accuracy that can further muddy the waters.

It's better to moderately overexpose than to underexpose negs. If you are one stop over, the effects will usually not be very obvious- particularly if you are scanning the negs for printing. I tend to err on the side of overexposure if I'm not sure about what the camera is telling me.

If what you are doing works for you, by all means continue doing so. However, I know from hard-won experience that it is unwise to assume that results from a limited sample will be the same for everyone.

[titrisol]

Use a Silver battery, error is less than the latitude of film. My dad used SR bateries in the spotmatic since the late 70s/early 80s
Original battery was 11.2X3.6mm D,H
From the ones mentioned:
387S (11.6x3.6mm) is a 394 with a rubber spacer, said 394 battery (9.5x3.6mm) is cheaper and works fine. If you want the spacer you can use a piece of electrical tape

PS. you made take my Spotie out, only had a 384 battery (LR41); and yes that one works with the helpof an o-ring and some electricla tape to hold it in place

[LisaXXDavidson]

According the info from Pentax, the meter (the circled M uppercase on the schematic) has an internal resistance of 3 Kohm. They also say that the needle is centered when a current of 3uA (microAmp?re) traverses the meter. Hence a higher voltage battery will give a higher current at centre, so the needle will be off!

So then is this not really a bridge circuit, even though they call it one?

[Xmas]

So then is this not really a bridge circuit, even though they call it one?

It is a bridge circuit, but not balanced.
The zero on the meter is at a small current.
If you were using transparency film you need to worry.
If you are using mono be happy!
But I’d check the meter bright and low light as the old cells can age.
A good repair person would replace and recalibrate.

[LisaXXDavidson]

Thank you! That's terrific.

[Luna Grace]

Honestly, your best bet, and I completely support it when I use it myself, is to get a CRIS adapter. It's more expensive upfront, but the only batteries I know are zinc-air batteries that have the right voltage, but they're expensive and don't last long. You get a CRIS adapter and you can use a 1.5v silver oxide button cell to enjoy the benefits of the battery's cheap, abundant availability and long continuous life. It's a very easy adapter and is explicitly built to be spotmatic (among others).

best-camera-for-fashion-photography

But as I know, both the SPII and the previous SP have 'bridge circuits' that allow the voltage to be regulated so that a 1.55v battery should function fine. I am also using the adapters, however.

[womble]

I use an adaptor like that. Expensive initial outlay but then works fine and the replacement batteries are cheap as chips. As I rotate round my various film cameras the zinc air battery didn't work for me. By the time I wanted to run a second roll through the Spottie, the battery was flat.

[fog.photo]

I have a Spotmatic SP500 and I put a SR936 battery on it

There's an issue, though. The needle of the lightmeter moves up when I put a slower shutter speed, but it doesn't move if I open the lens.
So the lightmeter only seems to be sensitive to the shutter speed - but even so, it has a weird behaviour - at 1/8s, the needle is at the center, but if I move to 1/4th, the needle immediately jumps down to the bottom

What is the issue here?