# PX625 and PX675 (in a Konica TC)



## JGOB (Feb 27, 2016)

Hey,

I have a couple of film camera's and a X100T which I use to check if the lightmeters on my film camera's are still working. 

My X100T gives the same reading as my Konica T3N (I tested at ISO1600 and a shutter speed of 1/250 with gave me f5.6 in both cases. I had the Konica T3N converted to use normal batteries (i.e 1,55V silver oxide batteries) but it used to run on PX675. Before the conversion I used 1.4V zinc-air hearing aid batteries (which are luckily also labeled 675) to replace the PX675. And they worked fine.

Now I recently acquired a Konica TC. I wasn't actually going for the TC but for the three Hexanon lenses that came with it. So I thought the TC would make a nice birthday present for my 10 year old niece who told me she wants to be a photographer when she grows up (yay!).

Been testing the light meter but at ISO1600 and 1/250 the meter reads f2.8. Two stops off. I tested it with film, I compensated for the two stops and the film turned out fine but of course this makes it a lousy present. 

I tested the TC with two 675 zinc-air batteries. I still have lots of 675's because I still use them in my Konica Auto S3 rangefinder. They have the same voltage, they're just smaller, so it didn't seem like a big problem. But because of the wrong reading on the lightmeter I am doubting this. 

Is it possible that they would give a different reading? 
Is the lightmeter faulty?
Could there be another reason the lightmeter is 2 stops off?
If I would put a couple of 1.55V silver-oxide batteries in, would it (partially) compensate or would it make it worse?

Thanks!


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## timor (Feb 27, 2016)

Did you try on any other setting than  ISO 1600 ? Did you get in readings any other aperture, than 2.8 ? How the light meter works on ISO 100 ?. This is an old camera after all. Electronics may not work as intended.


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## cgw (Feb 27, 2016)

timor said:


> Did you try on any other setting than  ISO 1600 ? Did you get in readings any other aperture, than 2.8 ? How the light meter works on ISO 100 ?. This is an old camera after all. Electronics may not work as intended.



Agree. It's a 40 year-old camera whose meter is likely off, so battery swapping probably won't deliver what you're after. Working meters aren't always accurate meters, sadly.

Matt's Classic Cameras: Konica Autoreflex TC

Probably not welcome advice but I'll offer it anyway. Get the newest 35mm film gear you can afford. Film and processing aren't cheap, so old iffy cameras can quickly prove a false economy.Repairs are getting pricey and hard to find. It's often cheaper simply to ditch old gear for newer stuff that may lack retro cachet but works consistently.


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## compur (Feb 27, 2016)

Battery voltage specs are nominal, that is, they are not exact and can vary (from one battery to the next or one manufacturer to the next) by a small amount which can be enough to affect vintage camera meters. Battery voltage levels also drop in use and their actual initial voltage is often a bit higher than the battery's nominal spec.

Also, even when those old film cameras were new and loaded with the batteries they were designed for they didn't all give the exact same readings for the same lighting conditions. The standards for what is or isn't a "correct exposure" has always been subject to a certain degree of interpretation by manufacturers. And, the ASA/ISO numbers written on film boxes have always had a certain amount of "fudge factor" as well.

Bottom line is you have to test to see what does or doesn't work in an old camera. No one can predict what a 50-year old meter will do when powered by a certain battery that the meter wasn't designed for.

Disclaimer: The above is, as always, my opinion. Others' opinions may vary. 

As an example, not too long ago I tested the meter on my friends OM-1 using 2 different batteries: a Wein cell (1.35v) and a current alkaline version of the (formerly mercury) PX625 (1.5v) and the OM-1's meter gave me 4 stops difference between them! I was amazed at the difference that 0.15 volts made!

Would I get the same result with any OM-1? I have no idea.


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