Weird detail to Chinon CS out of range indicator

I just got one of these (actually the slightly modified version for GAF, the L-CM) day before yesterday, and it's already the first m42 camera I've really really liked. It's more usable than my Prakticas, more polished and comfortable than my old Yashica that broke, and it has a level of convenience that obviously you don't get on a Zenit E, plus it can use lenses that the Zenit can't. I'm especially looking forward to trying some daylight flash fill on this the way I do on my Nikkormat, since it syncs at a very usable 1/125th.

But there's something weird about one of it's more helpful features. See, it has normal plus-minus exposure brackets and a needle like on a Pentax or a Nikkormat. It resembles a Nikkormat FT viewfinder closely, more so than a Spotmatic But then it has a special triangular warning flag that rotates out directly behind the needle. The manual says that this comes out at speeds so slow that the meter cannot accurately meter for the film speed. The flag appears to be geared directly to the film speed dial inside the shutter speed dial so that it rotates out progressively as a certain speed is reached on the shutter speed dial. The flag appears at about 1/8 when the film speed is set to 1600 (technically in the black space past 800) and so on.

This all makes sense and is well and good. Nice to see a feature like that. BUT, there's more to it than that. As you continue to go down past the speed at which the flag rotates into the viewfinder, the meter needle is mechanically raised first to the center of the flag and then to the upper edge. There is no sensitivity to light at this point, and the merer doesn't have to be on for this to happen. It is as if the entire galvanometer was being rotated.

What is this meant to indicate? Just a little signal to the photographer that they're going the wrong way if they're trying to leave the "red zone?" An indicator of how many stops you are past the edge of effective sensitivity?

I had the almost identical CX, and don't recall the red flag. It sounds like the CdS (?) light meter has limited range, and the flag indicates "you're on your own here" with a mechanical rather than electronic signal. I agree the Chinon is a very likeable camera.

blockend said:

I had the almost identical CX, and don't recall the red flag. It sounds like the CdS (?) light meter has limited range, and the flag indicates "you're on your own here" with a mechanical rather than electronic signal. I agree the Chinon is a very likeable camera.

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As I say, that's the reason for the flag, but I don't understand why the needle raises up when you turn the dial past that point. I don't know what that indicates, since it can't be something specific about the light, but it seems to be very deliberate.

Maybe it is catching on something. Has the camera ever been disassembled?

ic-racer said:

Maybe it is catching on something. Has the camera ever been disassembled?

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I wouldn't know. I bought it at a garage sale on Saturday. No tool marks. And anyways it seems too mechanically smooth for it to be parts catching and moving each other unintentionally. It seems like a very deliberate and precise mechanism that's meant to communicate something beyond just "you're out of range."

It seems to work well enough. The shutter is quiet and sounds right at all speeds, almost identical in sound to my Nikkormat FTn. I will say that I just put a new Px625A because the one I had in it at first was almost dead, and it does still tend to overexpose like it's not getting the full voltage. It does seem linear enough when you increase the film speed setting to compensate... almost as much as I compensated it for the flat battery before, but it wasn't linear then. Maybe this battery was expired when bought it? It has been hanging up on the shelf in the camera store for a while.
I have pictures of the viewfinder with the flag and the needle in various positions taken with my phone. I was surprised... not all viewfinders come into focus on my phone camera. I'll post them once I'm at a phone charger.

Here's the pics. This is what it looks like when you rotate down past the shutter speed where the flag comes out. They may not be in order. The position of the needle goes from low to high in steps.

In the manual (here: https://www.butkus.org/chinon/chinon/cs/cs.htm), it says that:

(2) When an ASA setting is used in conjunction with speeds and/or apertures which are beyond the range of the TTL meter, a red signal will appear in the exposure zone of the viewfinder (Fig. 17). When the red signal appears it indicates that a flash unit should be used to supplement existing light.

The meter has abandoned ship, and heading to the + is the camera's way of telling you so. I wouldn't worry. If the camera behaved weirdly in normal light, or the needle dragged subsequently, I would be more concerned. The Chinon CS goes back to a time when adding LED traffic lights would have put another couple of hundred on the price of a camera. Staying full analogue meant the store cupboard could be plundered one more time, and the numbers were more consumer friendly. Doing a comparative test with another meter will allay any fears. Your problem will be finding a cost effective way of replacing the mercury battery. If someone's been in there first with a zinc hearing aid cell and some cooking foil, that might be responsible for metering anomalies.

Seems very much like it's just an indicator of how far below the meter's working range you've set your shutter. Red flag = lower meter limit (based on film speed and setting). Red + needle rising = -2, -3, -4, -5(?) stops below meter limit. In theory, that would let you set shutter speed via the viewfinder display without having to pull away and look at the dial.

blockend said:

The meter has abandoned ship, and heading to the + is the camera's way of telling you so. I wouldn't worry. If the camera behaved weirdly in normal light, or the needle dragged subsequently, I would be more concerned. The Chinon CS goes back to a time when adding LED traffic lights would have put another couple of hundred on the price of a camera. Staying full analogue meant the store cupboard could be plundered one more time, and the numbers were more consumer friendly. Doing a comparative test with another meter will allay any fears. Your problem will be finding a cost effective way of replacing the mercury battery. If someone's been in there first with a zinc hearing aid cell and some cooking foil, that might be responsible for metering anomalies.

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Yes, as I said: the red flag is the camera telling me it can't meter. That's what I've known all along, given that it's both clear from the context and explicitly stated in the manual. I'm not mad, but everybody seems to have a bit of a problem about not reading the OP's post on this forum, I think.

However, there seems to be more to the needle moving than that. Donald's theory is intuitive but it still seems a little weird to me.

Is it that the galvanometer body is always rotating when I turn the dial, so as to show the correct exposure, and that there is something that holds the needle down when the meter is off? And the needle rising is the point at which it overcomes that force? That's just a thought. I know there were stop-down cameras where the linkage between the shutter-and-film-speed selector (which is the only linkage) and the meter was purely mechanical like that.

At any rate I checked the Px625A in my SRT and the needle hits the middle of the check indicator where the flat battery wasn't even touching it, so that's something. May still be a little low... I would expect a fresh alkaline to go even a little past the check box on the other side, since the voltage ought to be higher than the mercury batteries the camera was designed for. The SRT emphatically does not compensate for over voltage when using the meter, unlike some cameras.

RLangham said:

but everybody seems to have a bit of a problem about not reading the OP's post on this forum, I think.

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I wasn't sure whether it was the practicalities of the metering system that troubled you, or why electronics made it behave in the way it did. My distant recall of the Chinon and other needle and match needle metering systems of the day, is they behaved similarly in certain modes, like B and T. I assume it was a primitive means of showing the range was no longer reliable, and the flying or dying needle emphasised the point. The electronics behind it was not something that detained me.

blockend said:

I wasn't sure whether it was the practicalities of the metering system that troubled you, or why electronics made it behave in the way it did. My distant recall of the Chinon and other needle and match needle metering systems of the day, is they behaved similarly in certain modes, like B and T. I assume it was a primitive means of showing the range was no longer reliable, and the flying or dying needle emphasised the point. The electronics behind it was not something that detained me.

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No, nothing's troubling me. I don't think the camera is operating wrong. I'm just curious as to whether there's a separate meaning to the needle moving distinct from the known meaning of the flag. It's especially weird to me that the manual says nothing of this in the section where it discusses the red flag. I thought somebody might know.

I will say this is not an electronics thing. This looks as though the needle is being lifted from its resting position mechanically, and I'm not sure but I think it does it without a battery in. I'll test that assumption in a minute.

EDIT: it does it exactly the same without batteries.

Disconnekt said:

In the manual (here: https://www.butkus.org/chinon/chinon/cs/cs.htm), it says that:

(2) When an ASA setting is used in conjunction with speeds and/or apertures which are beyond the range of the TTL meter, a red signal will appear in the exposure zone of the viewfinder (Fig. 17). When the red signal appears it indicates that a flash unit should be used to supplement existing light.

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I mentioned in my initial post that I'd read the manual and knew that much...