What do the green/orange/M settings do on an older auto-thyristor flash?
Asked 7/15/2024
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I have an older flash with a green/orange/M switch on the front. It seems to cover or uncover a small opening, which may be a light sensor. There’s also an exposure chart on the back with colored rows.
What do the green, orange, and M settings mean, and how should the chart be read for each mode?
Originally by sleepy6758. Source · Licensed CC BY-SA 4.0
sleepy6758
1y ago
2 Answers
15
That is an auto thyristor flash. The thyristor shuts the flash off after it sees a certain amount of light based upon the setting (green/orange), and the setting is essentially a power setting.
In manual mode with the thyristor disabled/blocked the full power of the flash can use the entire scale, to include the orange row. It will always use full power.
With the thyristor enabled at full aperture (orange) it can also use the full scale including the orange row. Only it may (or may not) shut the flash down before full power is used, based on the reflected light sensed.
And with the thyristor enabled with the restricted aperture (green) it can use the full scale up to/including the green line. It may also shut the flash down before all of the available power is used. Due to the restricted aperture the flash must put out more light before the thyristor receives enough light to cause it to terminate the flash. I.e. at 6m the green mode will put out two stops more light than the orange mode.
Originally by Steven Kersting. Source · Licensed CC BY-SA 4.0
Steven Kersting
1y ago
0
Generated from our catalog & community — verify before relying on it.
This is an auto-thyristor flash. The opening is the flash’s light sensor, which measures reflected light and cuts off the flash when enough light has returned.
- M = manual mode. The sensor is blocked/disabled, so the flash always fires at full power. Use the chart’s manual distance/aperture guidance for your film speed (ISO/ASA).
- Orange = auto mode with one auto range, typically the longer-distance/higher-output range. Set the aperture indicated by the orange row for your ISO, and use distances within that orange range.
- Green = auto mode with a different auto range, typically a shorter-distance/lower-output range. Set the aperture indicated by the green row for your ISO, and stay within the green range.
How the chart works:
- Pick your film speed/ISO (ASA) column.
- In manual, ignore the colors and use the manual/full-power guide.
- In orange or green, set the flash to that color and set the camera aperture to the matching f-stop shown in that colored row. The usable subject distance is limited to that mode’s range.
Use a shutter speed at or below your camera’s flash sync speed.
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