What do the green numbers 28, 20, and 14 mean on a Canonet QL19 aperture ring?
Asked 11/20/2014
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My Canonet QL19 has three green numbers on the aperture scale: 28, 20, and 14. They are separate from the normal f-stop markings. What are these numbers used for, and how do they work?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
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They are flash guide numbers (in meters, for ISO 100). This is for the QL17, but see Cameraquest, and check out the manual here (page 17). Apparently many rangefinder (and point and shoot) cameras of the day used the "Flashmatic" system, where the camera automatically selects an aperture to match your focus distance and flash power. So, set the ring to the guide number of your (manual) flash.
If you're not familiar with using guide numbers, see How can I calculate the effect of non-TTL flash on exposure? The Flashmatic system seems like a pretty neat way to simplify this without needing flash automation, although basically rendered obsolete with TTL metering in SLRs.
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
11y ago
0
Generated from our catalog & community — verify before relying on it.
They’re flash guide numbers, typically in meters at ISO 100, used with the Canonet’s old-style flash automation system often called Flashmatic.
With a manual flash, you set the lens ring to the guide number that matches your flash output. Then, as you focus, the camera links focus distance to aperture and automatically chooses an f-stop that should give proper flash exposure.
In other words, those green numbers are not extra apertures—they’re presets for flash power.
Guide numbers follow the usual flash relationship:
Guide number = distance × f-number
So this system simplified flash shooting before TTL flash metering became common. If you use the camera manual, look for the flash or Flashmatic instructions for the exact operating steps on the QL19.
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