Spotmatic SPII meter needle

[fenderslash]

Hi all,

I'd just like to crosscheck an issue with some other Spotmatic users out there. I was reading "The Asahi Pentax Way", which said that when the meter is switched off the needle rests in the centre. In other words with the meter switched off it looks like it is showing correct exposure. I have two SPII bodies and on both of them when the needle is at rest with the meter switched off it points significantly lower than the centre "correct exposure" position. It's not way down low by any means, but as I mentioned it is significantly lower than centre. Is that what other Spotmatic users here see in their cameras too?

The reason I'm asking is that I've noticed that my cameras' "correct exposure" actually seems to be one to two stops overexposed on both of my bodies. For example, in a "sunny 16" situation (confirmed by my hand-held meter) the meter on one body indicates correct exposure at at f11 and on the other body it is the click-stop between f8 and f11. Both cameras had their light meter photo cells replaced about three years ago, so I was wondering if the reason was something as simple as the needle being out of calibration.

If a few people could check their SP or SPII bodies and let me know where their needle rests I'd really appreciate it. I believe the SPF used a different kind of meter so that model may not have any relevance to my cameras.

Thanks in advance.

 

[Steve Smith]

The off position and the correct exposure position should be in the same place. i.e. the centre of the needle's travel. This is because correct exposure is shown when there is no current flowing through the coil of the meter.

This is why these cameras meter correctly with any cell you can fit in there and make contact with regardless of voltage. It even shows correct exposure if it's put in backwards but moves the wrong way for under and over exposure.

If your needle is bent out of place then correct exposure will be at the place it rests when switched off. You can do a quick check on that using the sunny 16 rule.


Steve.

 

[Steve Roberts]

I don't know exactly how far adrift the needle is from your words "significantly lower than the centre". With the meter switched on, you could measure by varying the aperture setting how far from the centre in stops the needle is resting. Spotmatic meters tend to vary quite a bit anyway, both in terms of their actual reading and the speed of response of the needle. Also, whilst the Sunny 16 rule is a handy stand-by, it's far short of 100% accurate and I wouldn't even try to compare a hand-held meter's reading with the Spot's TTL system. You don't suggest that you've had any poor results from either camera, so it could be that you're worrying unnecessarily. There's an old saying that "If you go looking for trouble, you'll usually find it."
Hope you resolve the issue.
Steve

 

[Steve Smith]

Also, whilst the Sunny 16 rule is a handy stand-by, it's far short of 100% accurate and I wouldn't even try to compare a hand-held meter's reading with the Spot's TTL system.

I agree. I wasn't suggesting it would be as accurate but if a sunny 16 reading (or a reading from a different meter) shows similar settings to the Spotmatic needle using its (currently wrong) off position as the correct exposure position then I think it's safe to consider that the meter's needle has been bent out of place.


Steve.

 

[fenderslash]

Thanks to both Steves for the quick replies.

The off position and the correct exposure position should be in the same place. i.e. the centre of the needle's travel. This is because correct exposure is shown when there is no current flowing through the coil of the meter.

This is why these cameras meter correctly with any cell you can fit in there and make contact with regardless of voltage. It even shows correct exposure if it's put in backwards but moves the wrong way for under and over exposure.

If your needle is bent out of place then correct exposure will be at the place it rests when switched off. You can do a quick check on that using the sunny 16 rule.


Steve.

What you're saying backs up my suspicions. The needles don't appear to be physically bent, so it appears that they are just resting in the wrong position. I'm hoping that there's some kind of calibration that can be done on that in the long term, but in the meantime I now have a workaround to just set the exposure to the needle's normal resting place.

I don't know exactly how far adrift the needle is from your words "significantly lower than the centre". With the meter switched on, you could measure by varying the aperture setting how far from the centre in stops the needle is resting. Spotmatic meters tend to vary quite a bit anyway, both in terms of their actual reading and the speed of response of the needle. Also, whilst the Sunny 16 rule is a handy stand-by, it's far short of 100% accurate and I wouldn't even try to compare a hand-held meter's reading with the Spot's TTL system. You don't suggest that you've had any poor results from either camera, so it could be that you're worrying unnecessarily. There's an old saying that "If you go looking for trouble, you'll usually find it."
Hope you resolve the issue.
Steve

The next step will be to try your suggestion of varying the aperture and seeing if it reads what I think it should read when the needle lies at its normal resting place. I realise the Sunny 16 rule wouldn't be 100% scientifically accurate for this kind of experiment, however it was a nice sunny day and the rule says the exposure should be correct with the camera set to 1/125 at f16 with my 100 iso film, and I backed that up with a meter reading with my Sekonic L308S meter, so I'm pretty confident that the Spotmatic meters should read the same if they were functioning correctly. It's also true that I haven't had any poor results yet from the cameras, but I'm ashamed to say that I'm about a year behind with my developing so there may be some surprises waiting for me there.

 

[Hatchetman]

I do not comprehend. I have two Spotties. Both recently CLA'd by reputable sources. When off, the meter needle rests way down towards underexposed on both of them. If the needle rested in the middle, you'd constantly forget to turn on the meter. You'd think you were metering correctly when in fact the meter was off.

 

[fenderslash]

It sounds like yours is similar to mine Hatchetman. And what you say about the risk of thinking that the exposure is correct when in fact the meter is switched off is exactly what the "Pentax Way" book that I was reading warned about. Until I read that section in the book I didn't realise that the meter was supposed to be centered when switched off. A few days ago when shooting I was thinking to myself that the shutter speeds I was selecting via the meter seemed too slow for the sunny conditions, and then after reading that chapter of the book I started to put two and two together...

 

[Hatchetman]

I have no clue, other than to say both of my cameras meter perfectly as far as I can tell. I rely on the in-camera metering entirely. One of them was a new-in-the box 1973 version.

If you really want to get to the bottom of this, I suggest contacting Eric Hendrickson, Pentax "guru." http://pentaxs.com/

 

[Bill Burk]

Spotmatic II user manual doesn't mention it. I recall my dad's Spotmatic II needle was down slightly at rest. This makes sense as a "feature" because it will prevent you from mistakenly shooting with the meter off.

You know how to do a battery check, right? Set ASA at 100 and Shutter at B (one of the invalid combinations). Then when you slide the switch up the meter needle should drop rapidly.

Spotmatic F is different, it is always on.

Without battery in the F the needle rests in the middle. I recall being "bugged" by this because I can't just fire away if needle is in the middle. I have to check it responds to f/stop changes "just to be sure" the battery didn't connect. I have a hunch if I was already used to the practice, (if the SPII rested in middle) I wouldn't have been bothered with how the F works.

Maybe the author mistakenly attributed a feature of the F to the II.

 

[Dan Williams]

I have both a Honeywell Pentax Spotmatic and an Ashahi Pentax Spotmatic SP II. I bought both of them new and in both the needle angles down when the meter is off. They have always done this.

Dan

 

[fenderslash]

Thanks again for all of the replies. Judging by your comments my meter needle placement might be within the normal range. I also have an SPF that I am planning to send to Eric Hendrickson next week, so I was getting opinions here about the SPII meter so that I could send them along with the SPF if they were behaving abnormally compared to everyone else's. I'm doubting my theory about the meter needle now, however the settings definitely do seem to be a stop or two out so maybe there's another reason. I think I'll send them along to Eric with the SPF anyway and get him to either calibrate/fix them or give me peace of mind that nothing is wrong.

 

[jochen]

I have several SP II's and 2 SP's. In all of them the needle is below the centre when the meter is off but not totally down like with severe underexposure. When the meter is switched off the needle is mechanically fixed at this rest point to prevent it from swinging caused by movements of the camera. There was only a change in the needle rest position during the early series of the SP in the sixties.
If your measurement result is different between 2 bodies and against an external meter or another camera the reason could be ageing of the CdS cell. But Asahi used very stable cells, all of my cameras are o.k. A Practica MTL 5 (from about 1983) which I bought for 5 € has a deviation of -2 EV-stops, this seems to be very common for aged CdS cells from East Germany. The meter can be adjusted to a certain extend by a service technician or by a skilled amateur, you can find the service manual for the Spottie in the net. I hope you will have a lot of fun with these cameras and their beautiful lenses.

 

[Steve Smith]

Copied from a post I made on Photo net earlier:

I have checked my four Spotmatics and the meter needle on all of them rests just below the zero position. A bit of research has shown that the Spotmatic circuit actually applies a very small offset current through the meter at correct exposure so my comment about zero current flow at correct exposure was not fully correct (although it's such a small amount that the principle is still the same).

I found this:

However, the Spotmatic circuit is offset slightly so the correct exposure reading is slightly off of centre with a small amount of current flow. This was done (I think) to enable the battery check function to work).

What this means is that the Spotmatic circuit is slightly voltage dependent but not by enough to worry about in normal use.

The embarrassing thing is that I wrote it myself about three years ago!

 

[fenderslash]

Thanks again to everyone who is taking the time to give their insights here.

I have several SP II's and 2 SP's. In all of them the needle is below the centre when the meter is off but not totally down like with severe underexposure. When the meter is switched off the needle is mechanically fixed at this rest point to prevent it from swinging caused by movements of the camera. There was only a change in the needle rest position during the early series of the SP in the sixties.

That last sentence might be the missing piece of the puzzle regarding what I thought should be the needle's normal resting place. The "Pentax Way" book I've been reading is a first-edition from 1966. Could it be that the rest position changed from dead centre to down a little in the underexposure region after that book was released?

 

[jochen]

Hello,
the Spotmatic was presented on the Cologne Photokina in autumn 1964 and first sold late in 1964. If your book edition is of 1966, maybe the early series are meant. On weekend I will look into my Pentax book whether I can find something about the early rest position of the needle.

 

[Ricardo Miranda]

Hi!
That is true, several modifications were made to the Spotmatic during its run.
The original Spotmatic had the needle resting on the centre and the needle was also smaller. The switch was also much narrower and with a small round window. That was changed to a larger switch without a window. Asahi was always improving the model!

 

[Bill Burk]

A bit of research has shown that the Spotmatic circuit actually applies a very small offset current through the meter at correct exposure.

When the meter is switched off the needle is mechanically fixed at this rest point to prevent it from swinging caused by movements of the camera. There was only a change in the needle rest position during the early series of the SP in the sixties.

It all adds up. They did it on purpose. And I know why they did it! It's so obvious. Asahi engineers realized with the normal rest at perfect exposure there would be many mistakes of shots taken with the meter off. When you know you have to put the needle in the middle... It doesn't take long to realize the meter is switched off when the needle doesn't move in response to shutter speed - f/stop changes.

Now I have to rationalize why it changed with the F, back to rest at the middle. I could give the engineers credit that they knew users literally could not forget to switch it on. Or I could anthropormorhize them (ascribe normal human traits) and assume they forgot about the previous improvement.

 

[jochen]

here the information from "Gerjan van Oosten, The Ultimate Asahi Pentax Screwmount Guide, 1999", page 58: ".....Resting position of the light meter needle improved since June 1966 (points to the "-"-sign...."

 

[fenderslash]

Thanks Ricardo and Jochen. Mystery solved

I had been planning to send an SPF and some Takumar lenses to Eric Hendrickson, which I did today, so I sent the SPII bodies along for the ride too with a request that Eric check the meters and recalibrate them if necessary.

 

[Hatchetman]

Just FYI, he sends you an "invoice" which is really just an estimate for work pending. I thought he was done with the work. I called a few weeks later wondering where the camera was. He said he hadn't started working on it yet. But he got to it shortly and the work he did on a moldy lens was amazing.