SEI Exposure Meter - how to calibrate?

Hello,

I recently acquired a working SEI Exposure Meter. It is I think a late version, with a metal rather than black button switch and a bulb soldered into a threaded brass mount.
At first I thought it had been modified by a previous user because it didn't look exactly like the pictures I had seen, including the instruction manual. However Mike Butkus has two version of the instruction manual, mine looks like the model in what appears to be a more modern booklet - https://www.cameramanuals.org/flashes_meters/s_e_i_photometer.pdf. This includes an illustration and explicit mention of the soldered bulb.

What's frustrating me is that I'm unable to get consistent readings when comparing with two other meters (Vivitar 45 and a DSLR) which I do know measure correctly and agree with each other.

In general the readings are out by at least 3 stops. I've tried the approach of setting the scales to my known readings and then adjusting the rheostat so that the dot disappears at that point, as mentioned in several other places. However when I subsequently try to take a reading of something else that is out again.

I have a feeling that there is something obvious I'm missing. I've read various articles and blogs, including Robert Suomala's but nothing quite covers it. Does anyone have any tips or suggestions?

Thanks,

Sig.

You should save yourself a lot of grief and send the two meters out to be calibrated together at the same lab. Believe me it is worth the cost to have all your light meters calibrated the same and correctly.

Sirius Glass said:

You should save yourself a lot of grief and send the two meters out to be calibrated together at the same lab. Believe me it is worth the cost to have all your light meters calibrated the same and correctly.

Click to expand...

Thanks, that is always an option but it would have to be a last resort as I'm doing everything on a shoestring!

Have you verified "standard brightness" via the microammeter on top? Also, the SEI has a very narrow field of view which, IMO, would make it difficult to ensure you're reading the exact same area with all meters. I can't imagine this would result in a 3-stop difference, but thought I'd mention it.

Here is a service manual for the SEI. It is a very complex mechanical and electrical device compared to normal photoelectric meters like your Vivitar. I would not try to service one myself, but unfortunately there seems to be no one in the world willing to work on them anymore.

https://learncamerarepair.com/product.php?product=172&category=2&secondary=37

I recommend backlighting a frosted panel with an amount of light that’s about the top of low range and about the bottom of the middle range. Great if you can move the light behind the panel back and forth to make it brighter and dimmer.

On the speed dial there is a shadow (black) and a highlight (white) dot. Mark a line halfway between white dot and black dot. Example black dot on ASA 10, White dot on ASA 1000 - make a mark opposite ASA 100. This would be what agrees with your other light meters.

Then as you have been doing, use one of your meters to read that backlit panel, dial in the same reading for the same ASA on the SEI photometer. Then twist the rheostat at the bottom of the base to make the light spot disappear.

That should be calibrated and if the indicator on top moves nicely, you can mark on a piece of tape, where the needle is pointing. If the needle doesn’t work you can come back to your light standard (backlit panel).

You should certainly not be off by three stops anymore.