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ẸWÀ ÀTI ÌLERA
IṢẸ́ ỌWỌ́
ÀṢÀ ÀTI ÌTÀN
ÌṢERÉ
ÀYÍKÁ
OÚNJẸ ÀTI OHUN MÍMU
REVERSE ENGINEERING
SÁYẸ́ǸSÌ
ERÉ ÌDÁRAYÁ
ÌMỌ̀-Ẹ̀RỌ
ÀWỌN OHUN WÍWỌ̀
Photoelectric Exposure Meter
Photographers judged exposure by eye, by printed tables, or with extinction meters that asked them to read the dimmest visible number. Edward Weston (the instrument maker, not the photographer) used a photovoltaic cell that generates its own current in light and fed it straight into a sensitive meter marked in exposure terms. No battery, no judgement.
**US 2,016,469**, "Exposure meter", Weston, assigned to Weston Electrical Instrument, filed 31. December 1931, granted 8. October 1935: an instrument "for the direct determination of the correct exposure conditions", improving on earlier current-generating cell meters whose output was too small and whose construction was impractical.
**You build the same thing** from a small solar cell and a multimeter, calibrate it against a lux meter, and turn its readings into shutter speeds.
Olùbẹ̀rẹ̀
90 minutes
Ìlànà
1
1
Cell and meter
Cell and meter
Clip the solar cell's two leads to the multimeter set to DC milliamps (or microamps). This short-circuits the cell through the meter - the current is what you read.
Àwọn ohun èlò fún ìgbésẹ̀ yìí:
Solar Cell Mini - 350mV1 ẹyọÀwọn irinṣẹ́ tí a nílò:
Òǹwọ̀n iná mànàmáná onírúurú
Alligator to Alligator Cables2
2
A hood
A hood
Glue a black card tube 30 mm long around the cell so it sees only light from in front, as Weston's meter did.
Àwọn ohun èlò fún ìgbésẹ̀ yìí:
Káàdì dúdú tí ó nípọn1 ewéÀwọn irinṣẹ́ tí a nílò:
Ọ̀bẹ Iṣẹ́ Ọwọ́
Ìbọn ìlẹ̀mọ́ gbígbóná3
3
Calibrate
Calibrate
Hold the cell and the lux meter side by side, facing the same way, in four very different lights: a dim room, a lamp, a window, open shade outdoors. Note both readings each time.
Àwọn irinṣẹ́ tí a nílò:
Ohun ìdíwọ̀n lux4
4
Current to exposure
Current to exposure
Ń ṣí ìwé Jupyter…
5
5
Use it
Use it
Stand at the subject, point the hood back towards the camera, read the current, and set the camera manually from the notebook's table. Compare with the camera's own meter.
Àwọn irinṣẹ́ tí a nílò:
Òǹwọ̀n iná mànàmáná onírúurú6
6
History & Context
History & Context
**What the patent specifies:** a light-sensitive current-generating cell connected to a measuring instrument reading directly in exposure terms. **Modern build (derived):** a silicon solar cell and a multimeter.
Weston's selenium-cell meters, sold from 1932, made metering routine; cameras later built the cell in. Its limits: selenium cells lose sensitivity in dim light and age, and any meter averages the scene - a snowfield or a black cat still fools it.
Àwọn ohun-èlò
2- Solar Cell Mini - 350mVìdá 10%1 ẹyọ$2.22
- Àyè
Àwọn irinṣẹ́ tó nílò
5- $3.58
Àpapọ̀ Ìfojúsùn
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