Canonet QL17 GIII Q about the 20, 28,14 on aperture ring

[mekia02]

I have looked in the manual to figure out if those are just aperture settings or what they are and it is not mentioned in the manual. On the aperture ring to the right of the "A" there is 28, 20, and 14 I have never seen an aperture smaller than 22, so are those numbers just more aperture settings?

 

[Leighgion]

My understanding is that those are special settings for use in combination with the dedicated Canon flash and to be ignored in normal use.

For the record though, apertures go as small as the hardware supports. While it's common for f22 to be a min, I have several lenses that go to f32 and as you get to larger formats, you can get smaller and smaller.

 

[BobD]

They are not aperture settings. They are flash guide numbers.

 

[mekia02]

thanks

 

[Farkle-Mpls]

I played with the auto flash settings on this camera a couple years ago. If I remember right, there's nothing magic about them in regards to having to use Canon's flash. If you can adjust/reduce the output of your flash to the corresponding guide number (e.g. 28, 20, 14) the whole system works fine.

 

[MattKing]

FWIW, the guide numbers themselves are in meters, not feet.

 

[Mike Wilde]

I believe the system was called Flashmatic by Olympus. It presumes you have an electronic flash that does not have an auto exposure eye.

Early electronic flash were modelled to replace flah bulbs, and who ever thought to turn off a flash bulb half way through ingniting it?

So photographers were familar with guide numbers for flash. Guide numbers came (and still do) in feet and meters, and were specific to the spped of film being used, although with electronic flash the guide number that the flash was rated by was based on an iso 100 speed film sensitivity.

The numbers you give indeed suggest meters. When put into auto flash mode, the camera's shutter speed is set at 1/60th or something similar, and the focus distance drives the aperture used.

Say you have a GN20 (M) flash. Set the 'flashmatic ring' to 20, and then as you focus to 4m, the aperture will effectively be f/5, or 2 m, set to f/10 etc. You see, a flash guide number is the product of aperture and distance to give the correct exposure for a given film sensitivity. Soime settings will prevent a close in focussing, since the aperture can only go so small ( like f/22) and thus too much light could be getting to the film at short distances.

 

[MattKing]

I don't know that it was called "Flashmatic" (that may have been an Olympus term ) but otherwise, what Mike says is correct.

The flashes that Canon designed for the camera were called "Canolite", and the particular model was the Canolite D.

There is a full description of how to use the system in the manual for the camera, a copy of which can be obtained from Mike Butkus' site here (a donation would be an excellent idea):

http://www.butkus.org/chinon/canon/canonet_g-iii_17/canonet_g-iii_17.htm