Selenium Lightmeter Preservation

[clarence]

Hello,

I hope this isn't too off-topic, but I realise that we have some members here who are extraordinarily well-versed in these arcane subjects.

I was wondering if its possible to prolong the life of still-functioning selenium lightmeters by completely shielding them from light, say, by wrapping black electrical tape over the selenium cells and keeping them somewhere dark inside their cases.

Would it have any effect on the longevity of these meters?

Thanks.

Clarence

 

[Jocko]

I believe this is true. My own experience suggests that selenium meters kept in the dark will remain functioning for a good long time. I have a built-in meter on a cased Isolette L which is still spot on after 46 years. A cased Kodak accessory meter from the 1950s also functions perfectly. Likewise I find my Leningrads are fine - I bought both of them around 1985.

I have also read suggestions that keeping the meter dry is important - in other words not stored in a humid area, which I think one would generally avoid anyway!

Cheers, Ian

 

[Avi999]

Hello Clarence
You are absolutely correct !
Hiding the cell from light is the way to keep it alive longer !
Tape is a solution though I prefer a removable non sticking material
so I can remove/attach it quickly.
I usually use a thin black opaque plastic foil or black thin foam material
to make those covers.
Have fun
Avi

 

[clarence]

Thank you, gentlemen.

I just got a bunch of selenium meters and now I'll know how to store them. With some care, maybe my children will live to see these strange devices.

Clarence

 

[Avi999]

Thank you, gentlemen.

I just got a bunch of selenium meters and now I'll know how to store them. With some care, maybe my children will live to see these strange devices.

Clarence

don't expect this... you'll save yourself some disappointment... 🙂
My Weston Master II 735 and Weston Master V-748 needs some
new Selenium cells so if you are left with those parts, I'll be happy
to trade.

Avi

 

[Sonnar Brian]

I always go for cameras kept in their fitted cases. I have lots of cameras and meters with working selenium cells, usually quite accurate. My oldest isa Weston 650, pre-WWII. It was kept in its fitted case. Add Canon 7, Retina IIIc, Retina IIIS, Retina Reflex-S, Nikon Meter III, Contax IIIa, ...

List goes on.

 

[ErnestoJL]

The two worst enemies for a selenium cell are humidity and temperature. The second (in order of importance) is light.
Extremely high light levels makes the cell to bring it´s maximum output (current) but at some extent and if exposed to very bright light for an extended time period, the chemicals inside react and output current is reduced. If this occurs, the light meter´s galvanometer won´t receive enough current to full scale deflection.

If the cell is exposed to a high humidity and/or high temperature, the effect seen from the user´s side is the same. Humidity gets in because cells are not protected in any way. They are a piece of iron covered with Selenium sulfide, and it´s completely exposed with just two wires for connection purposes.

Many old cameras (Contax III; IIIa; Kiev 3 & 4; some Kodak/Nagel Retinas, Agfa´s Silettes, etc.) had shutters ¡n front of their Se cells to avoid excessive light and thus extending cell´s life.

Ernesto

 

[wlewisiii]

I think Ernesto has it right as it's corrosion of the parts (from humid storage) that seems to be the biggest problem for these meters. IME and all that.

I've got a ZI Contessa, a Canon 7 & a Sekonic L-28c that are very accurate. The Contessa has a little shield for use in bright light. The Sekonic has it's bright slide and leather case. The Canon 7 doesn't have a case over the cell, but seems to do well anyway. Perhaps due to the hi/low switch?

I also have three GE PR-1's and one of these days I'm going to send the nicest one (orig box, manual & incident attachment - thanks Scott!) to QLM for a $65 makeover (includes new cell IIUC!).

Yep, I like selenium. It's got it's limits, but work with them rather than against the and you have a really nice meter. The Sekonic is within 1/3 of a stop of my friend's recently calibrated Luna-Pro. Somehow I think that's good enough for me 🙂

William

 

[wyk_penguin]

As with many things, when they work, they work. And when they don't, err.. let's not talk about that.

 

[ErnestoJL]

The worst thing with selenium cells are that they are chosen based in their current capability, it is how many micro amps they can deliver to the meter at a certain voltage. Then, when replacing the cell it´s not allways easy to find the right replacement cell.
Worst of all, the meter should be adjusted (when it´s possible) for the current drive to be enough to full scale deflection of the pointer.

Anyway, they work without batteries, and that´s good.

Ernesto