Interesting Canon FT meter observation

mtnbkr · May 9, 2022

I don't know if this is by design or represents a malfunction, but it's not something I've seen with other vintage cameras I've owned.

I was checking the FT's internal meter against the phone app I have and noticed when I set the shutter speed below a certain value, the meter needle would jump to the top of the viewfinder and no change to the aperture would affect it. For example, if the shutter is set to 1/30 and the needle indicates I need more exposure, moving to 1/15 or slower would cause the needle to do this. But...this was dependent on the ISO setting. At 400, I'd have to drop to 1/8 for this to happen. At 100, it wouldn't happen unless I selected 1/2 or slower. At higher ISOs, the shutter speed that would cause this reaction goes up. At 1600 it was 1/60 or slower that causes the reaction. In all cases the needle would jump without actuating the DOF/Meter lever. Maybe the combination of settings was exceeding the metering range and this was how it warns the user?

The meter is accurate otherwise and at the film speeds I use (100 and 400) the slowest meter-able speeds are at or below the speeds I use, so it's not a problem per se, just unusual.

That said, I also noticed my meter was pretty close to spot on even with a fresh 1.5v battery. Where my phone indicated 1/50 shutter speed, my camera showed 1/60, so slightly underexposed (not enough to notice with B&W print film).

Chris

wiltw · May 9, 2022

The Canon FT sensitivity range is spec'd at ISO 100 to work down to f/1.4 at 1/4 (using a f/1.4 lens) That appears to be consistent with your described exposuree. Below that, the optional booster is needed. So that might be simply Canon's way to indicate 'use the booster'. (It is not explicitly stated, though.)

An independent review (published by Rockwell) gives a hint about the meter operation:

"While most match-needle meters attempt to show the entire meter range along their scales, the FTb meter scale only covers the range of apertures of the mounted lens. The meter needle's position auto-ranges as the shutter speed and apertures are set."

BTW, the FT was designed to use the 1.35V constant voltage mercury oxide battery. Many meters do not work always accurately when 1.5V alkaline is substitute, as during its lifetime it declines from 1.5V down to about 1.25V, and the meter is 'accurate' only when it is about 1.35V. An Olympus OM-1 is like that, and in fact the degree of error is also variable depending upon the brightness of the light being measured! I did that test myself when I still had a mercury oxide battery to compared against alkaline. Cameras which use a Wheatstone Bridge circult can use different voltage without affecting meter accuracy...no idea if FT has this type of circuit design. And unfortunately I cannot find anyone stating the result of testing for accuracy of alkaline in lieu of mercury cell in the FT. Most info on the web about the FT simply says to use the MR9 voltage adapting converter with silver oxide cell, or use the Wein air cell.

Be aware there are so-called 'MR9" offered on eBay today that do not voltage convert but which force you to use the shorter life hearing aid air cells...do not buy one if you can see an air hole in the photo of the adapter!

randyB · May 9, 2022

First off: You have the wrong battery, the meter is designed for the 1.35 volt mercury battery which is no longer made in the USA. While the 1.5 volt battery will make the needle move the reading will be off by a few stops. You can use a hearing aid battery.
Second: Yes, it is designed that way. The metering settings are controlled by mechanical linkages. There are limits, this should be explained in the owners manual.
My experience with cameras of the vintage of the FT are that the metering cells have lost some of their responsiveness and will be very sluggish.

gone · May 9, 2022

Going from a 1.35 battery to a 1.5V battery is a relatively small increment. I usually don't even even reset my meter in these instances, but a hand held meter to ck & confirm exposures is very handy to have. My stash of button batteries came from cameras that I sold, and sitting around for a while in a drawer, they're pretty near 1.35V anyway. On an old camera like yours, just be grateful that the meter works at all. My FT and FTb cameras all had dead meters so I just used a hand held one.

mtnbkr · May 9, 2022

wiltw said:
The Canon FT sensitivity range is spec'd at ISO 100 to work down to f/1.4 at 1/4 (using a f/1.4 lens) That appears to be consistent with your described exposuree. Below that, the optional booster is needed. So that might be simply Canon's way to indicate 'use the booster'. (It is not explicitly stated, though.)

BTW, the FT was designed to use the 1.35V constant voltage mercury oxide battery. Many meters do not work always accurately when 1.5V alkaline is substitute, as during its lifetime it declines from 1.5V down to about 1.25V, and the meter is 'accurate' only when it is about 1.35V. An Olympus OM-1 is like that, and in fact the degree of error is also variable depending upon the brightness of the light being measured! I did that test myself when I still had a mercury oxide battery to compared against alkaline.
Unfortunately I cannot find anyone stating the result of testing for accuracy. Most info on the web simply says to use the MR9 voltage adapting converter with silver oxide cell, or use the Wein air cell.

randyB said:
First off: You have the wrong battery, the meter is designed for the 1.35 volt mercury battery which is no longer made in the USA. While the 1.5 volt battery will make the needle move the reading will be off by a few stops. You can use a hearing aid battery.
Second: Yes, it is designed that way. The metering settings are controlled by mechanical linkages. There are limits, this should be explained in the owners manual.
My experience with cameras of the vintage of the FT are that the metering cells have lost some of their responsiveness and will be very sluggish.

I'll be damned. It's right there on page 20 of the manual. I didn't recognize the implication when I read that page though. That said, I don't recall the TL (stripped-down version of FT) doing this, but that was nearly 30 years ago.

As for the battery, I've been using cameras of this vintage, including an OM-1md, since the early 90s (when they were merely old cameras and not "vintage collectables"). When I had the camera CLA'd last year, the meter was "adjusted", but I didn't ask how that was accomplished. All I know is my pics are exposed properly with the about half a stop or so extra exposure added (which may not be necessary, but it's how I used the other cameras of this vintage with a 1.5v battery).

The meter is plenty responsive. If it's "slow", it's no slower than the other ones I've owned.

Chris

mtnbkr · May 9, 2022

momus said:
Going from a 1.35 battery to a 1.5V battery is a relatively small increment. I usually don't even even reset my meter in these instances, but a hand held meter to ck & confirm exposures is very handy to have. My stash of button batteries came from cameras that I sold, and sitting around for a while in a drawer, they're pretty near 1.35V anyway. On an old camera like yours, just be grateful that the meter works at all. My FT and FTb cameras all had dead meters so I just used a hand held one.

I didn't know it was a problem with my first vintage camera (Canon TL in the early 90s). I just blissfully snapped away. I was made aware of it when I bought an OM-1md in 2001. The tech (was having it CLA'd) just said to set the ISO a bit lower or give it a stop or so of extra exposure. I did the latter, which then became habit, for the ten years I used that camera.

This FT seems to be spot on. The CLA invoice mentions meter adjustment, but it doesn't go into detail, so I don't know if that's adjustment to factory spec or adjustment to work with 1.5v batteries. All I know is adjusting exposure so that the needle sits on top of the circle results in a properly exposed shot.

People use old cameras with the Sunny16 rule and do ok, I can probably get by with a meter that's a bit off.

And yes, I'm happy the meter works at all.

Chris

Chan Tran · May 9, 2022

It's a good design to have the meter stops working altogether when out of range rather than continues to work but with unknown accuracy.

flavio81 · May 9, 2022

mtnbkr said:
I don't know if this is by design or represents a malfunction, but it's not something I've seen with other vintage cameras I've owned.

I was checking the FT's internal meter against the phone app I have

Suggestion: When you want to check if a camera meter is OK, always check against a dedicated (handheld) meter or a very good (calibrated) camera. Camera meter apps aren't as accurate, and will not necessarily "see" the same angle and pattern as your TTL meter and will not necessarily have the same color response, etc.

mtnbkr said:
and noticed when I set the shutter speed below a certain value, the meter needle would jump to the top of the viewfinder and no change to the aperture would affect it.

Yes, this is indicated on page 19 of the user manual.

mtnbkr said:
That said, I also noticed my meter was pretty close to spot on even with a fresh 1.5v battery. Where my phone indicated

The meter will not really be completely accurate over the whole light range if you are not using a 1.33-1.35V battery of constant flat discharge curve, like a mercury battery, or a zinc-air battery. Or a silver oxide battery with a diode to reduce its voltage.

flavio81 · May 9, 2022

wiltw said:
Cameras which use a Wheatstone Bridge circult can use different voltage without affecting meter accuracy...no idea if FT has this type of circuit design.

Hi Wilt,

It does not. It uses a system similar to the one in the F-1 (galvanometer physically turns when the speed dial turns), but with more provisions for adjustment.

btw, i love zinc-air cells.

mtnbkr · May 9, 2022

flavio81 said:
Suggestion: When you want to check if a camera meter is OK, always check against a dedicated (handheld) meter or a very good (calibrated) camera. Camera meter apps aren't as accurate, and will not necessarily "see" the same angle and pattern as your TTL meter and will not necessarily have the same color response, etc.

I've used the meter app in question to meter for several rolls of film in multiple cameras. I trust it as much as any camera-based meter.

flavio81 said:
Yes, this is indicated on page 19 of the user manual.

View attachment 305026

Yeah, I completely missed this detail when I initially scanned the manual. I don't know how I managed to not run into this with my TL (similar, but simpler camera), but I never did while using it in college.

flavio81 said:
The meter will not really be completely accurate over the whole light range if you are not using a 1.33-1.35V battery of constant flat discharge curve, like a mercury battery, or a zinc-air battery. Or a silver oxide battery with a diode to reduce its voltage.

True, but it's "close enough" for print film. I've always had fine results just adding a bit of exposure to whatever the meter read.

Chris

wiltw · May 9, 2022

flavio81 said:
Suggestion: Camera meter apps aren't as accurate, and will not necessarily "see" the same angle and pattern as your TTL meter and will not necessarily have the same color response, etc.

The above is why testing of any two meters would have a target which is a wall which is 1) featureless and 2) uniformly illuminated...so the designed use of any metering pattern or metering zone bias or selective metering area are NEUTRALIZED in pointing at that wall!

mtnbkr said:
True, but it's "close enough" for print film. I've always had fine results just adding a bit of exposure to whatever the meter read.

John Hermanson, the guy who started Camtech, an outfit which was an Olympus specialist, characterized 1.4V air cell error of 0.5EV (vs. mercury cell) and 1.5V alkaline cell error of 2-3EV for the OM-1. That amount of error might be OK in the direction of overexposure, but it really results in badly saturated color when the shot is underexposed. And for color slide it is fatal.

mtnbkr · May 9, 2022

wiltw said:
The above is why testing of any two meters would have a target which is a wall which is 1) featureless and 2) uniformly illuminated...so the designed use of any metering pattern or metering zone bias or selective metering area are NEUTRALIZED in pointing at that wall!

When I compared my camera's meter with the phone app, I used an 18% grey card taped to the wall and illuminated by the overhead light fixture. There were no shadows on the card and it was illuminated as evenly as possible. I backed away so the rectangle in the FT's viewer (the area I understand to represent the metered area) was about 3/4 the size of the card. When I repeated the test with my phone, I set the app to "spot" to ensure I wasn't metering off the bare wall. It's probably not lab-grade testing, but it'll have to do.

wiltw said:
John Hermanson, the guy who started Camtech, an outfit which was an Olympus specialist, characterized 1.4V air cell error of 0.5EV (vs. mercury cell) and 1.5V alkaline cell error of 2-3EV for the OM-1. That amount of error might be OK in the direction of overexposure, but it really results in badly saturated color when the shot is underexposed. And for color slide it is fatal.

John CLA'd my OM-1 back in 2001. I wish I still had that camera. I used it on my honeymoon that year and to take pics of both my kids until 2010ish.

As for the alkaline vs mercury cell metering differences, it may be that much, but I always just slightly overexposed (per the meter reading) and my pics came out. With my OM-1, I had the needle just barely touch the top of the box "opening". With my FT, I have the needle sit right on top of the little circle. I don't know how much that represents, but it works.

I suppose it's good I didn't say I use Sunny16*.

*I don't, I'm not good enough at estimating light.

Chris

flavio81 · May 10, 2022

mtnbkr said:
As for the alkaline vs mercury cell metering differences, it may be that much, but I always just slightly overexposed (per the meter reading) and my pics came out. With my OM-1, I had the needle just barely touch the top of the box "opening". With my FT, I have the needle sit right on top of the little circle. I don't know how much that represents, but it works.

I suppose it's good I didn't say I use Sunny16*.

You shouldn't use alkalines because the voltage isn't constant.

Sunny 16 is more reliable that a light meter with a completely wrong battery.

Now, it's your camera and you can do whatever you want. But what Wilt W. said is important -- once you try slide film you'll see how good or wrong the exposures were.

Interesting Canon FT meter observation

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