SEI Exposure Photometer

[Mark MC]

You can't imagine what a valuable resource this site is for people like me who have very little knowledge or expertise in the photography world. Thank you! I'm still working my way through this rather large collection of vintage photography gear (cameras, lenses, meters, etc.) that belonged to the father of a friend (Ken Howell). Today I pulled out a nice leather case that held a SEI exposure photometer in it and I've since learned it was made in the late 1940's to the 1960's which fits in with the rest of the collection.

It looks like it is a pretty technical piece of equipment. I went to examine the battery and discovered that the battery sleeve/tube and bulb are missing. I'm guessing that Ken removed it at some point to prevent a corrosion issue. It may well be in this collection somewhere but I have been unable to locate the sleeve. In looking online it appears that this is such a technical piece of equipment made 60-80 years ago that parts are difficult or impossible to find. I was hoping someone reading this post could point me in the right direction. I am assuming it will be hard to sell without the battery. Thanks again in advance! Mark

[David Lindquist]

I was hoping someone with more expertise than mine would answer. Don't worry about the battery, it's a standard D cell. You do need to find the bulb, it's frosted and specific to this instrument As far as I know the bulb was and is not used in other applications. AND the bulb goes in a base which is a machined brass disk about the inside diameter of the meter, so you need to find that too. I'm not aware of any current source of parts aside from what might appear on ebay.

Another potential problem is the selenium cell inside may be dead. This reads the brightness of the bulb so that it can be set using the meter at the top (the red line) and rheostat on the bottom. I'm not aware of a replacement source for these cells either.

This looks like it is in very nice cosmetic condition. Personally I find these to be a very elegant piece of instrumentation; more mechanical than electronic. Hope you can get it working.

David

[Mark MC]

Thank you David! Maybe it was the language in the English literature I was reading that led me to believe there was a sleeve of some sort that the battery fit in. Good to know that I just need a D cell battery. Now the hunt is on for the bulb! I couldn't find it in the collection. Do you know how to determine if the selenium cell is functional without having the unit operational?

[Greg]

The S.E.I. Photometer as you stated was made for around 20 years. The shape of the point of the needle is the best way to determine the age of the meter. Last ones made had a simple needle with no "arrowhead" at the pointer's end. Personally found (in the end) that the selenium cell is the first piece to go bad followed by the rheostat on the bottom. I acquired several broken S.E.I.s to finally put together a working one.
go to:
https://www.largeformatphotography.info/forum/showthread.php?158723-Tale-of-the-elusive-SEI-Photometer&highlight=photometer
I still have some parts from the broken Photometers. Please Personal Message me.
Greg

[David Lindquist]

Thank you David! Maybe it was the language in the English literature I was reading that led me to believe there was a sleeve of some sort that the battery fit in. Good to know that I just need a D cell battery. Now the hunt is on for the bulb! I couldn't find it in the collection. Do you know how to determine if the selenium cell is functional without having the unit operational?

There is/was a sleeve, just a thin piece of plastic rolled into a cylinder. I think it was to protect the insides from a corroding battery though it doesn't seem like it could have done that very effectively. Probably would be easy to improvise something.

Maybe the selenium cell could be tested by shining a light up the inside of the meter (the cell is up above where the battery goes; the bulb and its mounting disk go on top of the battery) and see if the the meter deflects? I don't know. Maybe Greg could comment.

And thank you Greg for adding your expertise here.

Some years ago I asked George Milton at Quality Light Metric if he worked on the S.E.I. He didn't, I think largely because parts were no longer available.

David

[Greg]

My belief is that the selenium cell's output was so little that it needed the power of the battery going through the rheostat to budge the needle. FYI: Someone, unfortunately long gone, offered to modify the Photometer to use a LED in place of the bulb. His info was on the WEB years ago, but wasn't able to find it last year. A replacement for the selenium cell was never offered as far as I can tell. Interesting posts at

https://www.photrio.com/forum/threads/sei-photometer-selenium-cell-replacement.136097/

Service manual at:

https://learncamerarepair.com/product.php?product=172

It is a free PDF Download... make a hard copy before it disappears.
Greg

[Mark MC]

David - you won't believe this but I just got off the phone with George Milton! He was fun to talk to - had some stories abut this device. He went back to the shop and actually found a bulb and photocell and will be shipping them to me. As you can tell from my photos, when I take the end cap off the unit all I have is an empty chamber. Is the D cell battery and light bulb all that I am missing? Mark

[David Lindquist]

David - you won't believe this but I just got off the phone with George Milton! He was fun to talk to - had some stories abut this device. He went back to the shop and actually found a bulb and photocell and will be shipping them to me. As you can tell from my photos, when I take the end cap off the unit all I have is an empty chamber. Is the D cell battery and light bulb all that I am missing? Mark

Could be, let's see if the bulb includes the mounting disk. And there's the possibility that the rheostat doesn't work...

Good luck.

David

[John Jarosz]

Ansel Adams (and Fred Picker) promoted the use of the SEI Photometer. Some thoughts:

99% of the meters in today’s universe don’t work because of what has been already said.
When they do work they are very accurate
It’s an extinction meter. You make an adjustment so that the area being metered blends in to the surrounding area
It is set up to measure Zone ll. I have Fred Pickers instructions on how to make the meter more ‘useful’.��
The image as seen thru the little telescope is upside down. You have to get used to it.
I also have instructions on how to convert it to a different lamp.
My SEI has the same issues your does. I decided long ago that the Pentax digital will do the job faster, easier, lighter, etc.
I can send you copies of my ephemera, or sell you everything I have. PM me if interested
It’s really something special from a bygone age. Things made today are not made like this. It is special.
But they are museum pieces

[John Layton]

Greg...that was Huw Finney who did what looked like the perfect modification (LED light source, upgraded electrics, updated scales) - and I wish I'd gotten my SEI to him in time! Would be great if someone else could take up the reins on this!

But many thanks for the SEI repair PDF - I've downloaded this and might just give it a go!

[William Whitaker]

Greg...that was Huw Finney who did what looked like the perfect modification (LED light source, upgraded electrics, updated scales) - and I wish I'd gotten my SEI to him in time! Would be great if someone else could take up the reins on this!


Exactly! I had contacted Huw some time back (>10 years ago), but was told by him that he didn't offer that modification anymore. Drat it!. I have two of the things, one of which was working correctly when I put them away. They're in one of my boxes, SOMEwhere!

[Steve Goldstein]

This may be of some value:

http://www.robertsuomala.com/5.html

[William Whitaker]

This may be of some value:

http://www.robertsuomala.com/5.html

Great reference. Thank you for sharing!

[Bill Burk]

Are you sure the bulb is not in there? If it is not there you will see a hole where the bulb would go. You could aim a bright flashlight in there. If the ammeter needle moves, even just a little, you will know the unit is complete.

I've got two of them, one almost working but with original parts and the needle barely moves. The other had corrosion that made the filters golden brown and so that one I tinkered with. I almost got a modern solar cell to work as a replacement for the selenium cell. But even that modification was too fiddly.

I bought a dozen 1.2 volt bulbs with round heads that are close to the right bulb for the job. I used sandpaper to frost the bulb.

When I use them, I tend to calibrate bulb brightness not to the internal meter, but to one of my other meters.

If the part is missing, it is "just" a disc of brass turned with a ridge and notched to fit over a pin. There is a nut that holds the bulb, though some versions solder the bulb in place.

[Mark MC]

Bill - thanks for questioning whether the bulb was there. It made me take a closer look. There was no hole where the bulb should go because the bulb was there the whole time! I feel like an idiot. The unit has the sleeve and the complete bulb assembly. I put a D cell battery in and pushed the little black button on the end where the battery inserts and the needle swung way over! I think this unit is complete and operational after all. Thanks again to everyone who contributed to this conversation. As I said, I'm gaining an education for sure. Now to find a buyer! God bless! Mark

[Matt Stage]

There is a classic video of Ansel Adams using such a device: https://www.youtube.com/watch?v=DQT_rzI1Xdw

[Mark MC]

That was very interesting - thanks for sharing! Mark