Quote Originally Posted by Kirk Keyes View Post
I have no ideas where to go for the UK. But most good camera repair shops should have a calibrated light soure to check your meter with.

"Never"
But that's kind of my point, how can one expect a measuring tool like a light meter that more than 50 years old, to be accurate? Add to that all issues Steve Benskin points out above...
You may be correct. The thought that they didn't last for ever never cross my mind until now. Perhaps it's time to get it serviced.

But. It does have user-calibration setting on the back. This is used to zero-set it.

And then. If it is out of calibration then that does not necessarily explain why the two readings differ. The sensor is the same one but in one case uses a diffusion cone and in the other not. Would this meter be sophisticated enough to have two separate calibrations, one for each mode of use?