How to use an SEI Photometer?

[Greg]

Used to use a SEI Photometer back in the early 1970s. Remember calling up Fred Picker and discussing with him how to use the meter with the Zone system. He sent me a copy of how he used his SEI. It was good starting point that I personalized in a short while. Well Fred, the instructions he sent me, and my notes on how I used my SEI are all long gone.

Just purchased a working SEI Photometer and want to start using it once the weather warms up (-15 degrees F last night). Anyone else out there use an SEI?

[Alan9940]

Never owned one, but Google is your friend: http://www.butkus.org/chinon/flashes_meters/s_e_i/s_e_i_photometer.htm

[Greg]

Never owned one, but Google is your friend: http://www.butkus.org/chinon/flashes_meters/s_e_i/s_e_i_photometer.htm

Thank you. Have been there.

Trouble is that SEI's official operating instructions were I believe orientated for motion picture film use. Fred agreed that the meter was user unfriendly for adapting it to the Zone System. But it was so repeatably accurate, that it was well worth the trouble. Very manual old world mechanical technology at its best. An extinction meter might just be the only more mechanical anti-digital device out there for measuring light levels. Only another person in this forum using unwieldily large view cameras would understand....

[Alan9940]

How about seiphotometer.net?

Good luck!

[Bill Burk]

Greg,

I have and use one...

I'm sure we could help you remember how you adapted it back in the day.

Mine has a tiny scratch between black and white dot. That is "about" where Zone V falls. I think a previous owner got tired of trying to figure out where to set the ASA and scratched it there.

I've been trying to reverse-engineer Fred Picker's "Taming the SEI" - you probably know the gist of it.

Did he wrap some kind of Zone scale between the black and white dots?

[Jerry Bodine]

Greg- AA tells how he uses the SEI in Camera and Lens. My copy is 1970, don't know if there's a later version. His discussion starts on p.73 and his method is outlined rather clearly. His method, which was to determine the luminance of a subject's area of interest (e.g., shadow) in units of candles/sq.ft., is fundamental to the use of his "exposure formula". Once he knew that result he was able to determine via mental calcs what shutter/aperture combinations would place that luminance on the desired zone. His view was that those mental calcs became easy with practice; I found that it hurt my hair trying to do all that in my head, so I carry a small calculator dial that I removed from an old Weston meter to use for finding the combos I wanted.

His Exposure Formula (which is only valid for luminances in c/sq.ft.) is:
Aperture = sq.root of the film's ASA (ISO)
Shutter = reciprocal of the c/sq.ft. reading
Example: a reading of 100 c/sq.ft. with box speed of 64 would mean that f/8 at 1/100s would place that luminance on Zone V. With that info one can figure out the adjustments needed to place that luminance on any desired zone, including correction for the tested EI.

This method no doubt proved useful for his Moonrise when he couldn't find his meter and no time to spare, but recalled that a full moon at that location in the sky was 250 c/sq.ft.

[Greg]

Found my copy of "Taming THE S.E.I METER" by Fred Picker
He assigns each of the films he uses with a personal f/stop
Tri-X f/22
Pan-X f/11
K-II f/8
Here is his outline of how he uses the meter in his words:
1. Set up the meter with a Zone Scale
2. Locate your personal f/stop - the one that delivers .10 density at the shutter speed that is opposite your Zone I sticker. Note that for this test the shutter speed stays the same for all exposures. Only the aperture is changed by 1/2 stops. The shutter speed is the one opposite Zone I.
3. In the field, meter, for example, a flesh tone. Note the shutter speed that appears opposite your Zone Vi sticker. Other values are then metered and will fall on the Zones opposite that speed.

My hand written note one side of the page:
Meter reads Zone II and Zone VIII+
On other side:
Set to read Zone V

Simply using my Pentax spot meter with its Zone dial looking lot easier to use... but then shooting with my FX digital one heck of a lot easier than hauling out the 11x14....

[Bill Burk]

OK that sounds like Fred Picker put his "Key Stop" idea into Taming the SEI.

It also makes sense Ansel Adams would be working in c/sq.ft because there are spaces for it in his Exposure Record.

[DennisD]

OK that sounds like Fred Picker put his "Key Stop" idea into Taming the SEI.

It also makes sense Ansel Adams would be working in c/sq.ft because there are spaces for it in his Exposure Record.

I, too, use have used an SEI meter for years. It's probably the best, along with the Pentax digital, for zone system work. Unfortunately, many SEI meters suffer from aging of the internal photocell used to calibrate the meter. In other cases, leaking batteries have claimed the lives of many SEIs.

Ansel's method of using the meter is great if you love numbers and doing mental calculations based on candle/sq.ft. luminance readings ! If you're good in this regard, it's definitely the way to go.

Fred Picker's method is somewhat gentler and enables readings off the SEI's table using zone markings you must add to the dial. Proper setup requires a bit of testing to determine calibration with your film, etc. Fred's setup and use of the SEI is described in his writeup, "Taming the SEI Meter."

I've posted a link to a PDF copy of Fred's "Taming the SEI Meter" immediately below:

http://www.jackandbeans.com/sei_picker.pdf

Fred's approach to using the SEI meter is very inventive and useful. A gift for those who don't enjoy mental gymnastics ! Thanks, Fred, wherever you are.

[Jim Andrada]

Another former SEI user here! Mine bit the dust some years back - would love to find another one. Best damned lightmeter I ever used (albeit heavier than some cameras)

[Bill Burk]

Thanks DennisD,

You made my day! I have been curious for a long time about what he figured out for the SEI.

[DennisD]

Another former SEI user here! ....
Best damned lightmeter I ever used (albeit heavier than some cameras)

Hi Jim,
Yes, heavier than a Leica, but nothing for us LF people who carry tons of equipment ! Besides, worth every ounce.
Your comment prompted me to weigh mine... I was surprised to find it weighs well over 1lb. w/battery.



Thanks DennisD,
You made my day! I have been curious for a long time about what he figured out for the SEI.

Hi Bill,
My pleasure ! Glad you found it interesting. Definitely worth understanding whether or not you use his method.

[John Layton]

Got mine cheap at a flea market - looks mint but not working...dang! Gotta get out my tools...

Awhile back, there was a guy named Huw Finney who offered an "upgrading" service for SEI's - replacing the lightbulb with an LED, recalibrating plus any other necessary repairs, then replacing the exterior exposure chart/scale with a truly "user friendly" version - much closer to what most of us are used to these days.

Don't know if Huw is still around - but if so, it would be great if he could chime in here at some point!

[ajmiller]

Repair manual and other info here

http://www.seiphotometer.net/repair.html

[Jerry Bodine]

...Don't know if Huw is still around - but if so, it would be great if he could chime in here at some point!

I recall reading somewhere that Huw is no longer offering his SEI fixes, but his website is still up:
http://www.huws.org.uk/

[Greg]

Repair manual and other info here

http://www.seiphotometer.net/repair.html

Thanks

[Bill Burk]

Got mine cheap at a flea market - looks mint but not working...dang! Gotta get out my tools...

If it's just the internal calibrator that's not working, you could still make use of the meter by calibrating to an external light source. If you have other light meters, you can calibrate that light source to one of your other meters.

If the light doesn't come on, that should be an easy fix. I've actually gotten tired of the weight and unreliability of the D cell (unreliable because a pack of good D cells costs 5 bucks so they are hard to keep around) and now I use an AA cell inside a dime-store shell the size of a D cell.

[John Layton]

Bill...interesting idea with going with AA's and the adapter shell. I'm guessing that the weight reduction would be significant...but what about battery life?

[Bill Burk]

Never thought about that. For me, the SEI is too "fragile" so I don't take it out in the field often. At home, there's always a bunch of fresh AA's around.

[Jerry Bodine]

For the benefit of those who don’t have access to AA’s ‘Camera and Lens’ (referenced in my earlier post), he set his black dot at 5 on the ASA scale, then takes the reciprocal of whatever exposure lies opposite f/8 on the lens stop ring, and that represents c/sq.ft., obviously viewing the result in the scale that corresponds to the range selected for the reading. These settings were a personally selected combination; the same result would be obtained by setting the black dot at 10 and reading at f/11 OR with the black dot at 20 and reading at f/16. The combinations were obtained by comparative tests of his SEI with sensitive instruments and light sources of known value. He goes on to say that shooting a high flare subject (e.g., against the light), where a significant amount of flare presents a definite false elevation of the low values, the use of the anti-flare tube accessory prevents this effect and all values read true.

FWIW, since I just got my Gossen meter back from re-calibration by Quality Light Metric, I took an 18% gray card reading with the Gossen and found the SEI agreed exactly with the black dot on 5 and reading at f/8. My anti-flare tube didn’t change the result, but then there was no flare involved with the gray card.

[Michael Whyte-Venables]

I find that the biggest challenge is identifying the Zone II feature from which to take a reading. I mean, you know where you are with an incident-light meter ...

[ic-racer]

I find that the biggest challenge is identifying the Zone II feature from which to take a reading. I mean, you know where you are with an incident-light meter ...

Both meter types have challenges and expertise is required for each. A barn photograph composition in the sun with one Illuminated wall and one wall in shadow will give different incident readings, depending if you are reading from the side in the shadow or the side in the sun. A zone II reflected reading will be independent of where you are standing.