Zeiss-Ikon Ikophot T meter

[hilltime]

I have these two Zeiss meters probably not far apart in age. Just took them out and inserted a fresh 9v battery and was checking their reliability as I haven't tested in a number of years. The white meter reads accurately outside in bright light 1/250@F5.6 ASA 100 and in a testing area (white wall) inside, 1/50@F4. Both are correct, confirmed with a more modern known value meter. The black version reads the same outside, close to 1/250@F5.6 ASA 100, but inside reading is remarkably different,
1/15@F1.4. Any reasoning behind this that anyone might know or guess? Would it be the failure of the CDS cell in a lower light condition or some other condition?
An inquiring mind would like to know......

 

[KoNickon]

The cell may just be losing its sensitivity in lower light as it ages. How old are these anyway -- 60+ years? These take a 9V battery?!

 

[Glenn2]

I have an Ikophot CD from the sixties which uses a mercury coin cell. I liked it a lot, but it’s lost accuracy so now sits on a shelf, replaced by a Sekonic L-308S.

For checking meters I made a Jpg file that’s pure white and matched to the resolution of my monitor. When this is viewed on a monitor it makes an evenly lit reproducible target to aim meters at for comparison.


Glenn

 

[Chriscrawfordphoto]

When metering cells go bad, they become non-linear. That means they may be accurate at one light level and off at a different light level. Very few old light meters are truly accurate or reliable anymore. For actual use in making photographs, a modern digital meter really is best.

 

[hilltime]

The cell may just be losing its sensitivity in lower light as it ages. How old are these anyway -- 60+ years? These take a 9V battery?!

Mid to late 60’s vintage as the white/ brown meter is a combo Zeiss/ Voigtlander product. The last production of Ikophot meters and using a common 9v battery. I have a few of the much more ubiquitous selenium meters with the leather case and gold foil logo which are accurate and working just fine. As a matter of fact, have probably 50 different meters from the 40’s thru the decades culminating with a Pentax spot meter. Never thought I’d develop a “collection “ of meters, but couldn’t resist the varied “coolness” of design.

 

[Cascadilla]

The community college where I teach has 20+ Pentax K 1000s that have CdS light meters. What I have seen many times as they age is under exposed negatives. I have frequently had students set the ASA at 200 or even 100 to deal with this problem and that usually works well enough for a beginning photo class. I know that Chris Crawford is right that these cells go non linear before they die completely, but the lower ASA settings have usually worked for my students. I do have reasonably accurate selenium cell meters from the 1950's--a couple of Zeiss Ikophots among them. They would not be my first choice for low light work, however.

 

[KoNickon]

I should have been more specific -- which 9 volt battery does it take? I think of the large rectangular ones with both terminals on one end. Are there others out there?

 

[hilltime]

I should have been more specific -- which 9 volt battery does it take? I think of the large rectangular ones with both terminals on one end. Are there others out there?

That's the one you have described.

 

[hilltime]

From Zeiss/Voigtlander Price List 1966. It was fairly pricey for that time!

 

[KoNickon]

That's the one you have described.

Thanks -- the good news is that these are readily available these days. A mercury 625 (like for the Gossen Luna-Pro), no.