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...photometer.htm

[Greg]

Never owned one, but Google is your friend: http://www.butkus.org/chinon/flashes...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)