Selenium light meter testing

Pseudodionizy · Jun 16, 2025

Hello, I've just got a really nice Olympus Pen EE-3, my only qualm is about the selenium light meter it uses, as I've heard they can be inaccurate or entirely nonfunctional. Mind you, this one works (I haven't yet had a chance to test it for accuracy), but I'm wondering if I can check somehow whether it's likely to expire soon, or if I can use it for at least some years to come... I haven't had much experience with this type of meters, so I wanted to ask: do they just die with no prior warning, or do they give inaccurate readings before giving up completely? Or is there any other way I could test its longevity? The camera came with a lens cap and the condition seems pretty pristine, as if it hasn't been used too intensively, so I'm hopeful that the selenium cell isn't worn out.

BrianShaw · Jun 16, 2025

If it works and resonably compare to another meter, then it works. If not, then it doesn't work. There is no way the I know of or can imagine to determine when it might fail. For the selenium celled meters I use, I keep them covered as much as possible but that might be just a habit and have nothing to do with increasing or decreasing their longevity. Only time will tell...

[Edots were typografical corrections]

xkaes · Jun 16, 2025

If it has a cap, then it's probably OK. I've got OLD selenium meters that have always been in the case or capped, and work fine. It only wears out when exposed to light.

Here's a pretty good way to test the meter. In normal use the shutter is 1/200, and the meter sets the aperture. Set the film speed at ISO 400. Open the back so you can look through the back of the lens. Point the camera at a bright object. Cock the shutter and release the shutter. You should see a tiny f-stop. Now point the camera at a dark subject. When you release the shutter, you should see a wider aperture. Try the same thing at ISO 25, and see if you see the same type of result.

If so, it's probably fine, but it's good to run a few test shots in bright and dark settings.

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F4U · Jun 17, 2025

What you want to look for is linearity of response across its range of sensitivity, just as a CdS or Silicon meter. Meter a gray card in the brilliant summer sunlight, or whatever it tales to get the meter reading a the top of its range. Similarly do it at the bottom end of it's range. Compare these readings to a known good meter of any kind. If one end is accurate and the other is off to an unacceptable degree, you have a weak selenium cell. It might be a good idea to do this at mid range also. The point is, what you are looking for is linearity. Meters typically go non-linear as they die. I've never seen one go week to an equal degree across it's range as it ages

Pseudodionizy · Jun 19, 2025

Thanks a lot for your advice and testing methods, that's exactly what I've been looking for! I appreciate it and I will try them out soon.

xkaes · Jun 19, 2025

Let I know how it works out. Since the Pen EE cameras -- there were several models -- are auto-exposure-only cameras without any exposure display, you can't use typical methods to determine meter accuracy. If your tests show that it works, just be religious about covering up the lens when not being used. A case or one of those "lens-cap-on-a-leash" things is a good idea.

Pseudodionizy · Jun 20, 2025

Okay, I've done some testing... The meter seems to be fine and reasonably accurate throughout most of its range, bottom, middle, except for the brightest light conditions where it seems to overexpose somewhat, I can never seem to get it to stop down to more than f/16.

F4U · Jun 20, 2025

I don't know what you mean by not letting you stop down more than f/16. Further I have no idea if Olympus made any provision to open up and readjust the calibration of the meter. The readings you are reporting here are in line with what I might have expected. It is possible and likely that the selenium cell has aged and gone non-linear, if it even was truly linear in response when new. I I were state outright that most selenium cells after all these years have gone bad, I feel confident it wouldn't be too far from the truth. If the meter wiring has a potentiometer you can adjust to "split the difference" between the high and low ends, it may help some. But I'd say the selenium cell is just dying a slower death that others. Some die fast, some suffer a slow agonizing death, like people. Not bad, really. considering the age of it.

xkaes · Jun 20, 2025

Where did you get the idea that the EE-3 stops down to f22? Maybe it does, but I don't remember seeing that. Maybe you've just reached the limit of the meter & light. The camera only has one normal speed (1/200?) and if the ISO and light in the scene are too high, it's going to "hit to limit".

Since everything else about it checks out, I bets it's OK, but there will be scenes it can't deal with -- too dark or too light (depending on the ISO.

One good thing about the Pen EE setup, is that in low light conditions, you can always use the flash settings -- without a flash. This sets the shutter speed at 1/45 (?) and you can dial in the f-stop, for great low-light shots.

Pseudodionizy · Jun 20, 2025

Well, it does have the f/22 setting in the manual mode so I figured it would be used in the auto mode as well, but yeah I considered that it might be beyond the meter's limit. I was doing it mostly in the ISO 400 setting to check the meter's upper limits. The manual says that the auto exposure range is EV(100) 9 to 17, but then I got confused when it comes to translating that to ISO 400 haha.

But either way it certainly seems pretty usable to me, I just got worried that it might overexpose in "sunny 16 weather", which is not extremely bright. But I think even that could be addressed with some exposure locking, if necessary. I'm going to do something of a test roll in different lighting conditions to see how it all translates to real film.

F4U · Jun 20, 2025

I bet there's an adjustment potentiometer in it. Actually the meter doesn't sound too terribly bad, considering its age. I'm not familiar with the camera, but typically any camera like that would certainly have an adjustment pot you can tweek. Being selenium cell, you know it doesn't have a lot of ability to deal with low light. So maybe a pot can be turned a hair to move the curve up towards the higher end. If i has 2 potentiometers, one would be for low and 1 for high. You might be able to have enough range on the pots to bring the meter closer to specs. There's no set rule that just because it's selenium cell and most of them are dead by now, doesn't mean they ALL are. I'm sure there's lots of guys using old Weston meters that still work fine.

MattKing · Jun 20, 2025

f/22 in a lens for a half frame camera probably raises diffraction concerns, so the metering system might be limited with that in mind.

xkaes · Jun 21, 2025

Pseudodionizy said:
Well, it does have the f/22 setting in the manual mode so I figured it would be used in the auto mode as well, but yeah I considered that it might be beyond the meter's limit. I was doing it mostly in the ISO 400 setting to check the meter's upper limits. The manual says that the auto exposure range is EV(100) 9 to 17, but then I got confused when it comes to translating that to ISO 400 haha.

But either way it certainly seems pretty usable to me, I just got worried that it might overexpose in "sunny 16 weather", which is not extremely bright. But I think even that could be addressed with some exposure locking, if necessary. I'm going to do something of a test roll in different lighting conditions to see how it all translates to real film.

There are plenty of other half-frame cameras that use f22 -- damn the diffraction, full speed ahead! I know the original Pen E had f22, so the EE-3 probably was designed for it, but that might depend on the circumstances. And you are right, with ISO 400 film, f22 would be correct for a sunny scene, but at worst it would be 1 stop over-exposed.

Sounds like you've got the best EE and in good shape. There really isn't any difference between the EE-2 and the EE-3, but the EE-3 is newer, anyway.

Happy shooting.

Ulrich Drolshagen · Jun 21, 2025

If the edges of the cells are well sealed they will still work fine. They do not deteriorate from exposure to light but from corosion of the selenium layer. I have four selenium meters, a Weston Master and three Gossen. Two of the Gossen are on my Rolleis. They too will die eventually but not any time soon while the sealant will last.

Ulrich

Pseudodionizy · Jun 21, 2025

Thank you all for your input, I really appreciate it! I've done some more testing today, and the meter seemed more accurate... or rather, the meter was fine all along but I misinterpreted the readings yesterday, and I corrected myself thanks to your suggestions. It does seem that this type of Pen doesn't use f/22 in the auto mode, and it does stop down to about f/16 in the brightest possible conditions. When I point it to a sunlit white wall, it does overexpose for the more sensitive ISOs, but I guess it has no other choice, considering how the aperture works, and it might be not the meter's fault. When I measured normal sunlit scenes, the results were generally pretty close to the CdS meter readings, perhaps with some overexposure for ISO400, but it was only about a stop or so, consistent with what @xkaes says, which should be generally of no practical importance.

So, I'm going to assume that my Pen is just fine We'll see how the test rolls turn out and if anything's wrong, I'll try out your fix suggestions.

xkaes · Jun 21, 2025

Don't forget to post some results.

Pseudodionizy · Wednesday at 8:10 PM

Hey, if anyone's still interested (like @xkaes haha), I'm posting some results from my test roll! The Pen seems to work just fine, even in bright sunny conditions. The darker shots (not included) underexposed somewhat, but that must be because of Fomapan 400's not-quite-400 sensitivity and the wide angle of the meter. Anyway, I'm very happy with the camera!

The film is Fomapan 400 developed in D76.

Selenium light meter testing

Pseudodionizy

BrianShaw

xkaes

F4U

Pseudodionizy

xkaes

Pseudodionizy

F4U

xkaes

Pseudodionizy

F4U

MattKing

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xkaes

Ulrich Drolshagen

Pseudodionizy

xkaes

Pseudodionizy

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