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09-24-2015, 08:42 AM   #46
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QuoteOriginally posted by pathdoc Quote
Okay, results. I put in an "InfiniCell" SR41W/392 cell, rated at 1.5 volts.

Using my SMC Takumar 55mm f/2.0 lens on both the Spotty and my K-5, I aimed at the same general area on my office wall (as close to the same spot as I could get every time). The lighting is practically all artificial, and the testing was completed within a few minutes, so I don't think natural lighting variations had any effect. The lens was wide open. I used centre-weighted metering on the K-5, with the green button in manual mode. Using spot metering on the K-5 made about another half-stop of difference SOMETIMES, depending on exactly where I pointed the K-5.

At 200ASA, the Spotty wanted 1/60 and the K-5 1/125.
At 400 ASA, the Spotty wanted 1/125 and the K-5 1/250.
The same relations were maintained at 800 ASA and 1600 ASA, which is where the Spotmatic quits.

Given that I cannot easily obtain film slower than 200ASA (200 and 400 are all I can easily get in the stores where I am), I did not think it practically worthwhile to continue the test at lower speeds.

CONCLUSIONS FROM THIS BRIEF TEST: With the InfiniCell SR41 or 392 cell, the Spotmatic would overexpose by one stop at every ASA setting, and I should set the ASA one stop faster than is on the cartridge.

I will subsequently test it against the Pentax P3 and/or P30T, so as to compare film camera against film camera and report back when this is complete.

ETA: I have a Pentax ME immediately to hand, and under the same conditions as above it renders the following results:
200ASA - agrees with Spotmatic (1/60)
400ASA - wavers between 1/125 and 1/250. I give 1/125 the benefit of the doubt here, especially considering that at...
800ASA - Agrees with Spotmatic (1/250)
1600ASA - Agrees with K-5 (1/1000)

Make of this what you will. The P3/P30T test will be the decider.
Even assuming your light meter adjustment hasn't drifted over the decades, there's still one annoying variable that might mess up your tests.
The Spotmatics used CDS photocells in the meter. Newer models like the P30T and the K5 use silicon cells. One of the several reasons CDS cells fell out of favour was they had greater sensitivity to the yellow/green end of the spectrum. So a camera that was perfectly adjusted for natural daylight would often read too high under tungsten artificial light - leading to underexposure - the opposite of what you're getting right now.
I remember getting fooled by my old Minolta SR-T 200 several times, making me think I could shoot under tungsten light without compensating for the meter's over reading. I'd get thin negs. Sometimes camera instruction manuals would warn you of the discrepancy. Mostly they didn't.
But the switch to gallium cells and eventually silicon cells solved that problem (unless you tried to take TTL readings through a red filter, when you were supposed to compensate again).

09-24-2015, 09:00 AM   #47
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QuoteOriginally posted by Ontarian50 Quote
there's still one annoying variable that might mess up your tests.
This is why I also used an ME, which is closer to the Spotmatic in all aspects of its technology than the others.

In any case, the meter is currently undergoing the practical test of an actual roll of film being put through it, in both daytime and artificial light. We shall see what comes of that, provided of course that my film-loading skills haven't atrophied (it's not as easy as the P3, that's for sure!). The first roll (taken unmetered on Sunny 16-type rules) went okay, but this one's making interesting noises. We shall see what comes of that, too. :/
09-27-2015, 08:33 AM   #48
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Using a spotmatic for ~15-years

Hi all,

I'm late to this party and skipped to the end after 'spotting' this thread (sorry) in a google search for spotmatic lug repair. I acquired an original asahi spotmatic (no 'sp', 'f', anything) about 15 years ago, and it has performed faithfully, albeit with some problems ever since (latest problem: a strap lug wore through while on a shoot yesterday, luckily I was clutching the camera at the same time I noticed the strap hanging loose on the shutter release side).

Problem: non-functioning TTL meter. Solution: hand-held meter.

Problem: 50mm f1.4 lens with uranium element(s) yellowing. Solution: after using >5 years, this has gradually cleared up. I guess there's a way of accelerating the process through exposure to strong light source, but that carries other risks (e.g. drying out lube/damaging finish?). This is a super-sharp, super-fast lens!

Problem: rewind button on bottom plate comes unthreaded, crippling film advance. Solution: I originally removed the bottom plate and tried 'gluing' the button on with nail polish on the threads, and lubricating contact area with the bottom plate with petrolatum. This worked for a few months until it didn't. Now I just manually rethread it, which it seems to need every 6-8 films. I can tell when the film advance doesn't do anything but cock the shutter -- usually while I'm trying to load a film. Once or twice I failed to notice until, I realized a 24-exposure film was pushing 30 frames! Or a film came back with erratic spacing/multiple exposures.

Problem: mirror locks up occasionally. Solution: that shot's blown, advance to next frame and carry on. Seems to happen every ~100 shots. Once or twice it took a few tries to clear up, while I speculated whether it was now dead.

Problem: slow shutter speeds unreliable. Solution: don't use.

Problem: flash sync busted. Solution: don't use.

Problem: strap lug wore through. Solution: I'd pay more attention to this in future (too late now). I did notice it was wearing excessively a few months ago, due to my poor choice of wire thingy attachment (triangular version of a d-ring?). Solution: researching now.

In spite of these issues the camera has generally performed well within these known limitations, and I've built up a collection of really good, fast prime lenses. One strength of this model is that thus far, I've experienced no issues with the light seals on a camera mfg > 40-years ago. Amazing.

I recently bought for a back-up/replacement body an Argus-Cosina stl-1000, an even heavier all-metal m42-mount slr of slightly later vintage, that comes with a copal metal fp shutter on board. It has it's own set of problems, but that's another story.

Looking forward to participating in this forum!

Thanks
09-27-2015, 10:23 AM   #49
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Mmm, have you ever thought that the solution to all your problem is simply to CLA the camera?

A complete service for a Spotmatic is not expensive at all, I think in the US they charge $60.

09-27-2015, 04:39 PM   #50
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QuoteOriginally posted by Cuthbert Quote
Mmm, have you ever thought that the solution to all your problem is simply to CLA the camera?
He could, but i think his post serves as a good example of how a tough, well-made camera can take a licking and keep on ticking.

I recently bought myself one of those cross-body straps that screws into the tripod mounting thread. I originally got it for a P30T which didn't come with a camera strap, and it will probably go across to an ME I recently bought, once I've ironed out a couple of small bugs. I'm not sure how it would go with a Spotmatic, though; I think the weight and shape might make it a bit awkward.

QuoteOriginally posted by dsmithhfx Quote
50mm f1.4 lens with uranium element(s) yellowing.
Thorium, not uranium. BTW I recently put a gamma counter against the rear element of mine and got about 20 counts a second, well above local background. Front element was mildly gamma-hot, but difficult to tell from ambient. I'm not overly concerned about it, but IMO it's not something you leave near your gonads unless you know you've finished having children.

I have to admit I didn't measure the activity with the lens mounted on the camera. Sorry. My bad.
09-28-2015, 07:38 AM   #51
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I've been pondering my options. As my wife will tell you, world + dog, I'm a terrible procrastinator. Suffice to say, none of those bad things happened yesterday when I put a couple more rolls through it, so I won't be sending it away tomorrow. Or the day after (can you see where this is not going?).

Also, I can buy another spotmatic in 'ex+/ex++' condition (whatever that means) for less than the touted cla + shipping. So there's that.

As for the strap, I went strapless yesterday and apart from being a tad more careful, wasn't much different from 'strapped', except the danged strap wasn't getting in my way. Risky, I know. I generally clutch the camera the whole time anyway. I do need a longer-term solution though. Debating the merits of pulling the top plate, which is probably the only good way, though risky for a klutz like me, vs. a glue job. I guess I could mess that up pretty good, too. I also have a flash bracket (attaching to tripod screw), which I might could adapt with minimal invasive/sticky mess, but could be clumsy, too.
09-28-2015, 01:51 PM   #52
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QuoteOriginally posted by dsmithhfx Quote
I can buy another spotmatic in 'ex+/ex++' condition (whatever that means) for less than the touted cla + shipping. So there's that.

Good luck with that!

No 50 year-old SLR will be 100% working unless recently serviced by a qualified tech.

BTW, wanna buy a bridge?

Chris
09-29-2015, 10:50 AM   #53
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QuoteOriginally posted by ChrisPlatt Quote
Good luck with that!

No 50 year-old SLR will be 100% working unless recently serviced by a qualified tech.

BTW, wanna buy a bridge?

Chris
I have two, 100% working, full-auto slrs: a Canon Rebel Ti, and a Sigma SA7.

Those are the cameras I leave home.

09-29-2015, 12:27 PM   #54
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Aaaaaand I've recently acquired another, thanks to coveting the lens that came with it (Super-Tak 35/3.5). This one has SP stamped on the top cover (no 500 or 1000) and appears in every way identical to the one I already have except for being an Asahi rather than a Honeywell. The shutter has a subjectively nicer click to it when fired than the Honeywell does. I think that's probably just sample variation. At some stage I'm going to swap the battery over and see how the meter goes, but that can come in its own good time.
09-29-2015, 12:35 PM   #55
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QuoteOriginally posted by pathdoc Quote
Aaaaaand I've recently acquired another, thanks to coveting the lens that came with it (Super-Tak 35/3.5). This one has SP stamped on the top cover (no 500 or 1000) and appears in every way identical to the one I already have except for being an Asahi rather than a Honeywell. The shutter has a subjectively nicer click to it when fired than the Honeywell does. I think that's probably just sample variation. At some stage I'm going to swap the battery over and see how the meter goes, but that can come in its own good time.
I would say more condition variation.
09-29-2015, 03:17 PM   #56
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At this stage of the game, the two are synonymous.
09-29-2015, 03:48 PM - 1 Like   #57
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I regards to the metering and batteries: Except for EV (at the sensor) near the low end of sensitivity or with an almost depleted cell, the metering should be just fine with modern batteries and should agree quite nicely with that from modern cameras.

CdS vs SPD vs. GPD photocells: Three factors fueled the switch to SPD or GPD. The first was response time. SPDs were fast enough for real-time metering on motor driven cameras. CdS, not so much with the sluggishness being more apparent in low light. The second factor was an additional 1-2 EV sensitivity extension on the low end. The third was "memory" after exposure to bright light which is not present in SPD or GPD. I have never heard of any issues with spectral sensitivity. It would be good to note that CdS meter cells were not uncommon through the 1980s. The last Pentax SLRs using CdS were the KM and K1000*. Today they are relatively uncommon, though not completely absent. I believe that most analog dial hand-held meters use CdS cells.


Steve

* One of the gating factors for CdS vs. other cells is how they work. CdS cells function as variable resistors and are best matched to analog needle displays. SPD and GPD cells are photovoltaic meaning that they generate current that is amplified and measured for electronic interpretation.

Last edited by stevebrot; 09-29-2015 at 03:56 PM.
09-29-2015, 05:06 PM   #58
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QuoteOriginally posted by stevebrot Quote
I regards to the metering and batteries: Except for EV (at the sensor) near the low end of sensitivity or with an almost depleted cell, the metering should be just fine with modern batteries and should agree quite nicely with that from modern cameras.

CdS vs SPD vs. GPD photocells: Three factors fueled the switch to SPD or GPD. The first was response time. SPDs were fast enough for real-time metering on motor driven cameras. CdS, not so much with the sluggishness being more apparent in low light. The second factor was an additional 1-2 EV sensitivity extension on the low end. The third was "memory" after exposure to bright light which is not present in SPD or GPD. I have never heard of any issues with spectral sensitivity. It would be good to note that CdS meter cells were not uncommon through the 1980s. The last Pentax SLRs using CdS were the KM and K1000*. Today they are relatively uncommon, though not completely absent. I believe that most analog dial hand-held meters use CdS cells.


Steve

* One of the gating factors for CdS vs. other cells is how they work. CdS cells function as variable resistors and are best matched to analog needle displays. SPD and GPD cells are photovoltaic meaning that they generate current that is amplified and measured for electronic interpretation.
I have found agreement with two different film bodies and 1 stop difference from a DSLR. Good enough to trust as far as I am concerned. We will see how the first roll of film works out.
09-29-2015, 08:36 PM   #59
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QuoteOriginally posted by pathdoc Quote
and 1 stop difference from a DSLR
If the dSLR had an adapted M42 lens mounted, 1 stop would be doing very well and I would give more credence to the Spotmatic.


Steve
09-30-2015, 03:52 AM   #60
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QuoteOriginally posted by stevebrot Quote
If the dSLR had an adapted M42 lens mounted, 1 stop would be doing very well and I would give more credence to the Spotmatic.


Steve
It did indeed. I used the exact same lens for all the readings.
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