Olympus manual focus slr light meter troubleshooting

jkfromsk · 2025-09-16T10:01:06-0400

I wanted to find out if the light meter (aperture priority) on my olys were accurate. So i did a lil experiment.

I used a blank white screen as a control variable and the Light Meter app on my iphone to get an "accurate" reading
I tested 200 ISO @ F/2.8 which came out to around ~1/200s

Heres what the cameras measured:
OM-10: 1/125s
OM-2N: 1/60s - 1/100s (?)
OM-2SP: 1/250s
OM-3Ti: 1/200s
OM-4Ti: 1/250s

I suspect there might be something wrong with my 2N, I havent been able to test film yet so im not sure. I could potentially compensate by adjusting the exposure comp knob, but im not sure how this might negatively impact performance
I know that until I test taking photos, I wont know how the camera works, my question is, could it be possible that the measurements will be inconsistent across cameras models and if so, how do i know if it will be accurate?

I am def by no means an expert on these things im mainly a collector who really fell in love with olympus cameras

wiltw · 2025-09-16T10:59:18-0400

One ASSumes that the light meter application is 'accurate'. Not necessarily true! I have to use the adjustment feature of the light meter app in my phone in order to get its reading to agree with a known-accurate spotmeter with 0.1EV precision and with the mid-histogram reading (which matches the spotmeter) obtained with my digital camera.

The same app installed on 2 phones from the same manufacturer (succesive models) does not agree with each other, if unadjusted reading, 1+ EV difference in reading
If unadjusted, neither phone agrees with my Minolta Spotmeter F.

phone 1: 1/6 f/2.8 ISO250
phone 2: 1/10 f/2.8 ISO250
spotmeter: 1/15 f/2.8 +0.2EV ISO250 (about 1/20 f/2.8 ISO250)

Keep in mindf that you could be introducing error in the OM-2n simply with the use of a battery other than mercuric oxide cell
...is the OM-2n meter modified, or are you using MR-9 adapter or using zinc oxide cell?

Chan Tran · 2025-09-16T11:50:01-0400

Besides that the light meter app can't be trusted on the OM-2 the indicated speed isn't the actual speed on auto mode. On auto what the camera doesn't care what the meter needle is pointing at. It uses a totally different sensor and measure the light during the exposure.

MattKing · 2025-09-16T12:01:04-0400

In addition, in Auto mode, all of those cameras except the ON-3Ti meter the light reflected off the film.
So whether or not film is in the camera has a big effect on the exposure.
In manual mode, the metering pattern of the different cameras probably differs as well, and may depend somewhat on the screen you have installed.

wiltw said:
Keep in mindf that you could be introducing error in the OM-2n simply with the use of a battery other than mercuric oxide cell

All of the cameras on @jkfromsk 's list use modern G13/MS76/357 batteries - no mercury involved.
Only the original M-1 and OM-1 used the 625 mercury cells.
Alkaline batteries that are nearly exhausted might be an issue though.

Paul Howell · 2025-09-16T12:04:55-0400

Use Sunny 16 to double check mid day, sunny sky, ASA 125 your camera meters should be 1/125th at F16. If you get same results as with the metering app then I would guess the meter in OM2 needs to be adjusted. But if the error is constant across ISO setting you can adjust the ISO (ASA) setting by one or one and half stops workable as long as your film ISO is in the middle of the pack ISO 100 to 400.

jkfromsk · 2025-09-16T12:24:49-0400

wiltw said:
...is the OM-2n meter modified, or are you using MR-9 adapter or using zinc oxide cell?

Im actually using x2 SR44 batteries. Is this not recommended? I heard it was good since it lasted longer than Li batteries

jkfromsk · 2025-09-16T12:25:15-0400

Chan Tran said:
Besides that the light meter app can't be trusted on the OM-2 the indicated speed isn't the actual speed on auto mode. On auto what the camera doesn't care what the meter needle is pointing at. It uses a totally different sensor and measure the light during the exposure.

I see, i assumed digital light meter would be pretty accurate.

jkfromsk · 2025-09-16T12:27:17-0400

Paul Howell said:
Use Sunny 16 to double check mid day, sunny sky, ASA 125 your camera meters should be 1/125th at F16. If you get same results as with the metering app then I would guess the meter in OM2 needs to be adjusted. But if the error is constant across ISO setting you can adjust the ISO (ASA) setting by one or one and half stops workable as long as your film ISO is in the middle of the pack ISO 100 to 400.

going to give this a shot later today.
so ISO 100 to 400 is the range where you can get away with ASA compensation?

jkfromsk · 2025-09-16T12:31:04-0400

MattKing said:
In addition, in Auto mode, all of those cameras except the ON-3Ti meter the light reflected off the film.

Ah i see, ill probably pop an expired roll in the 2N to try things out
and I also replaced all my batteries recently

MattKing · 2025-09-16T13:01:31-0400

jkfromsk said:
I see, i assumed digital light meter would be pretty accurate.

Your meter may or may not be accurate.
I believe that @Chan Tran was referencing the fact that all those cameras except possibly the OM-3Ti have two metering systems.
The one that provides a meter reading in the viewfinder, in case you are using manual mode.
And the separate system that controls exposure in Auto Mode by metering the light bouncing back off the film during the actual exposure.
EDIT: The OM-3Ti also offers OTF Auto Flash metering when used in conjunction with a compatible (usually Olympus) electronic flash.

Bill Burk · 2025-09-16T13:37:09-0400

On any OM - Check that as you move the f/stop on the lens that the reading changes by a stop each click. Sometimes the follower gets gummy and doesn’t register the f/stop.

On OM-2 -

I believe the displayed speed and the actual speed can vary especially in auto when the off the film meter circuit controls the shutter. (So you might get the right shutter open time even if the displayed shutter speed in the finder is different).

Of course you can’t test by ear without film because the off the film circuit will see black and give you a real long shutter open time.

wiltw · 2025-09-16T13:54:12-0400

Paul Howell said:
Use Sunny 16 to double check mid day, sunny sky, ASA 125 your camera meters should be 1/125th at F16. If you get same results as with the metering app then I would guess the meter in OM2 needs to be adjusted. But if the error is constant across ISO setting you can adjust the ISO (ASA) setting by one or one and half stops workable as long as your film ISO is in the middle of the pack ISO 100 to 400.

The results warrant CAUTION, as Sunny 16 is a rough guideline... 'about f/16'
I have metered with a known-accurate spotmeter targeted on an 18% gray card under clear blue sky (at latifiude 38) and gotten readings from a low f/11 +0.2EV (duirng Fall) ranging up to f/16 +0.4EV on various days. Right now, f/16 +0.4EV ((during Fall). Same wide ranging results using incident lightmeter with hemisphere pointed upward at the sun.

Paul Howell · 2025-09-16T15:59:59-0400

jkfromsk said:
going to give this a shot later today.
so ISO 100 to 400 is the range where you can get away with ASA compensation?

In general, it depends on the camera. I have many old mechanical cameras with dodgy meters. I have a Minolta 100 that is off by 2 stops over but it is almost linear. I compensate by setting 100 ISO film to 25, but shooing say ILford Pan F at 50 which I tested at 25 as my normal E.I for that film I would at the very bottom of the ASA setting at 8, which is not accurate. On the other hand, I have a few camera that read 2 stop under, which means I need to push the ASA up, some of by bottom feeder cameras meters top at ISO 400 or 800 so shooting even a 400 speed film is the a camera 2 stops over will not work. I keep masking tape on the back of my old cameras with how much they need to be adjusted. The trick to test each camera’s meters to see if the error is linear. As you have a nice collection of Olympus bodies I would try and find a tech who can calibrate the meter.

Kino · 2025-09-16T18:47:47-0400

One tangential warning: never take the front lens mount off an OM Series camera and start poking around inside. Models like the OM2 have a nylon string to adjust aperture to meter to viewfinder relationships and if one of the geared cogs in this path decides to jump a tooth or completely fall out, the camera is basically only good for parts. Very few repair persons will take on an OM2 with such issues. Ask me how I know...

Bill Burk · 2025-09-17T03:31:20-0400

@Kino I know and the bristles of the rheostat brush are like a prickly pine’s bump. You don’t just touch them

Flighter · 2025-09-17T03:35:36-0400

jkfromsk said:
Im actually using x2 SR44 batteries. Is this not recommended? I heard it was good since it lasted longer than Li batteries

You're using the right batteries, SR44 (silver oxide) are the batteries specified by Olympus.

Whilst LR44s (alkaline) will fit and work, they have a different discharge curve characteristic and can therefore introduce inaccuracies as the batteries deplete. Neither should Li batteries be used.

Olympus manual focus slr light meter troubleshooting

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