OM3 Light Meter Values Changing Depending on Lens

4r36 · Feb 22, 2023

I went back home and tried out all the Zuiko 50s I have as well as other focal lengths. I didn't find the grey card though, so I used the grey back cover of a book. It's more a 36% light grey than a 18% middle grey. You're more experienced than me, so tell me if this way the test is not reliable at all...

Strange enough, the spot metering reading was the same with all the 50s this time. Perfect exposure at f/2, 1/250s (ISO 250). The 100mm and the 28mm were 1/3 of a stop underexposed. I don't know whether this variation falls within the tolerances of the system. Personally, I don't care too much about such a small difference.

However, I do find strange the EV. At ISO 250, f/2 and 1/250s mean 8.67 EV. Tell me if I'm wrong, but that's pretty high. Evening-lit home interiors should have an EV of 5-6, lets's say even 7. But 8.67 is time squarish and I don't have any fluorescent lights at home xD. The reading of the meter app taken with the smartphone gave indeed an EV of 6.

I'm only more confused now...

4r36 · Feb 22, 2023

MattKing said:
The OP isn't metering and then exposing film. The OP is speaking of the reading available through the viewfinder. Even the cameras that do offer off the film metering - like the OM-10, OM-2 and OM-4, also have a separate metering system that feeds the viewfinder display. The OM-3 might as well, because I believe, but need to check, that it also has off the film flash metering.

The OM3 Ti has the off the film flash metering, but the OM3 doesn't

MattKing · Feb 22, 2023

4r36 said:
I went back home and tried out all the Zuiko 50s I have as well as other focal lengths. I didn't find the grey card though, so I used the grey back cover of a book. It's more a 36% light grey than a 18% middle grey. You're more experienced than me, so tell me if this way the test is not reliable at all...

Strange enough, the spot metering reading was the same with all the 50s this time. Perfect exposure at f/2, 1/250s (ISO 250). The 100mm and the 28mm were 1/3 of a stop underexposed. I don't know whether this variation falls within the tolerances of the system. Personally, I don't care too much about such a small difference.

However, I do find strange the EV. At ISO 250, f/2 and 1/250s mean 8.67 EV. Tell me if I'm wrong, but that's pretty high. Evening-lit home interiors should have an EV value of 5-6, lets's say even 7. But 8.67 is time squarish and I don't have any fluorescent lights at home xD. The reading of the meter app taken with the smartphone gave indeed an EV of 6.

I'm only more confused now...

By the way, for clarity and to make discussions easier, I find that it is better to say that a meter "reads 1/3 of a stop lower" than that a meter "reads 1/3 of a stop under-exposed".
"Under-exposed" is better used to describe the quality of a result.
At least part of the difference in your reading is due to the higher reflectance of your test object. There is at least one stop extra light reflecting back compared to an 18% grey card. And to give proper readings from a grey card, or for that matter any card, the card should be rotated about 20 degrees from being perpendicular to the lens axis. This helps deal with specular reflections from the surface of the card(s). Those reflections may also be playing into the differences between the metering results with a 28mm lens.

Bill Burk · Feb 22, 2023

I think the matrix pattern is only used in auto mode during firing. When the mirror is down, the meter reads a reflection off a secondary mirror behind the transparent mirror. Then the mirror goes up. A black curtain would cause a hiccup in the autoexposure reading. The matrix keeps the reading from blipping.

In flash the OM-3 wouldn’t need the matrix because the curtain should be already open.

4r36 · Feb 22, 2023

MattKing said:
By the way, for clarity and to make discussions easier, I find that it is better to say that a meter "reads 1/3 of a stop lower" than that a meter "reads 1/3 of a stop under-exposed".
"Under-exposed" is better used to describe the quality of a result.
At least part of the difference in your reading is due to the higher reflectance of your test object. There is at least one stop extra light reflecting back compared to an 18% grey card. And to give proper readings from a grey card, or for that matter any card, the card should be rotated about 20 degrees from being perpendicular to the lens axis. This helps deal with specular reflections from the surface of the card(s). Those reflections may also be playing into the differences between the metering results with a 28mm lens.

Thanks a lot Matt for the clarification and sorry for the lack of terminological precision. Good to know part of the difference in my reading is due to the higher reflectance of a lighter grey. I did rotate the book though. This weekend I develop the film and see what comes out.

Nicola

Jimskelton · Feb 22, 2023

BMbikerider said:
Really? The all the Olympus camera i ever owned had the meter reading taken off the shutter blind which was a type of matrix pattern of black and white squares. But the focal length of a lens was well known to give differing meter readings due to the acceptance angle of the light.
Have you tried it with spot metering with the light coming off a grey card and comparing it with that of a good hand held meter

The OM1 and OM2 both took a meter reading from a pair of photo cells near the eyepiece which was displayed by a needle in the viewfinder. There were some focusing screens which did not give an accurate reading. The OM2 calculated the shutter speed when set to automatic exposure from a pair of photo cells pointed toward the film plane. Fast shutter speeds were calculated before the shutter opened by metering against a matrix on the shutter. Slow shutter speeds were calculated by metering of the film plane. This is likely what you're referring to.

The OM3 and 4 both take a meter reading which displays inside the viewfinder with a photo cell located under the mirror pointed toward a mirror directed toward the lens, unaffected by light entering the viewfinder from behind or the focusing screen. There are 3 surfaces that could affect OM3 meter readings: The photo cell lens, the mirror which reflects the light forward, and the partially silvered main mirror.

Helge · Feb 22, 2023

Reason I gave up on OM. Always problems with the electronics.
Minolta, Canon and Nikon seems to hold up better.
And OM-1 with external metering is of course fine. But external metering is a whole other type of photography.

Bill Burk · Feb 23, 2023

I found a body fault in my OM-3 which might be part of the trouble. See if the aperture follower in the body springs back with sluggish action. I first noticed f/11 to f/16 not indicating any difference in reading, then after playing, it stopped indicating differences from f/8 through f/16. Then when I brought the follower where it belongs and mounted the lens at f/16… it indicated difference in exposure as I opened up to f/11 and f/8 but didn’t follow back towards f/16. I compared to an OM-4 and it is supposed to snap back nicely.

RalphLambrecht · Feb 23, 2023

4r36 said:
Hello everybody,

I would like to ask you some advice on how to deal with a problem I'm facing with my Olympus OM3.

Today I was shooting with a Zuiko 50 f2 Macro, and I got suspicious about the values the camera meter gave me. In my opinion, it was underexposing of about 1 stop . I changed the batteries to make sure they were not the cause of the problem (I replaced them a few days ago) but I was given the same values. Then I changed the lens, replacing the 50mm with a 28mm, which was CLAed recently. This time I was given -1 stop, so I wonder whether this means that the problem lies in the lens in fact. What would you do in my place? Would you send the 50mm for a CLA and keep the camera (which apart from this issue works flawless) or would you also have the camera checked? An OM3 without a properly working light meter is a real pity, so I'm undecided on what to do...

It might be the case there is nothing wrong. It may just have to do with different flair in the different lenses. Fill a roll of film with images from both lenses, measured with both lenses and see which one works best.

4r36 · Feb 23, 2023

Bill Burk said:
I found a body fault in my OM-3 which might be part of the trouble. See if the aperture follower in the body springs back with sluggish action. I first noticed f/11 to f/16 not indicating any difference in reading, then after playing, it stopped indicating differences from f/8 through f/16. Then when I brought the follower where it belongs and mounted the lens at f/16… it indicated difference in exposure as I opened up to f/11 and f/8 but didn’t follow back towards f/16. I compared to an OM-4 and it is supposed to snap back nicely.

Thanks Bill. I had a look but it seems to spring back finely and differences in reading are indicated at all apertures, although I keep having the impression that the meter reads always about 1 stop higher than it should, telling me to stop down. I bracketed a few shots, using the 50 macro but also the 28. This weekend I develop the roll and compare them. Thanks a lot for your help anyway!

RalphLambrecht said:
It might be the case there is nothing wrong. It may just have to do with different flair in the different lenses. Fill a roll of film with images from both lenses, measured with both lenses and see which one works best.

Yes, indeed. I hope to find it out in a few days

Bill Burk · Feb 24, 2023

Dang I took off the front and I think somebody was in here before me. There’s super-fine wire brush bristles that make the contact in the aperture sensor ring.

Half of the wires were trashed.

OM3 Light Meter Values Changing Depending on Lens

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