Tell me about using FD bodies in stop down mode

[iamzip]

Specifically the Canon A1, or something similar. It seems to me that, using stop down metering, the camera selects a slower shutter speed than if using aperture priority. Am I doing something wrong?

 

[iamzip]

That seems odd; an exposure is an exposure is an exposure. Could be a difference in the EV tables in the camera for the different modes.

I can verify when I get home (I have a couple of A-1 bodies and a 50L).

I would appreciate that, I just double checked it again. Using an FD 50mm f/1.4, the number shown in the display gets cut in half when I push the stop down lever - for example, if it reads "30" in aperture priority mode, then it reads "15" in stop down mode. I first noticed it with a Rokinon 28mm, on which the aperture was sticky so it had to be shot in stop down mode.

 

[bmattock]

That seems odd; an exposure is an exposure is an exposure. Could be a difference in the EV tables in the camera for the different modes.

I can verify when I get home (I have a couple of A-1 bodies and a 50L).

I was thinking it is possible that the camera or lens is malfunctioning mechanically, or the meter is simply not fast enough to respond during AE.

The FD, as you know, stops down to measure exposure during the exposure. If the lever that trips the aperture is not getting it all the way down before the measurement is made, it would be letting more light through than when on manual stop-down and manual metering. Alternatively, if the meter itself was not responding quickly enough - it might still be reacting to the light hitting it when it needed to report back a value and not yet have reached its final solution. Or the lens itself just might not be stopping down all the way when tripped automatically, but does when stopped down manually.

I don't know, just some thoughts.

The first thing I'd check would be a different lens on the same body. Then if I had a second body, I'd check that combination as well. Try to isolate it to a particular lens or a body.

I had an FL lens that would stop down manually properly, but when I tried to use it on my Canon FX (and FL body), in auto-stop down mode, it not stop down completely - the spring did not have enough tension. But the ring (some FL lenses had stop-down rings) did. So that's what made me think of it.

 

[bmattock]

One thing with the Canon A series is that once you use stopped down metering or DoF preview (basically the same thing) you need to recock the mechanism (you can use the multi-exposure button for this). I don't recall offhand if that was only when changing lenses; I know it had to be cocked when mounting a lens.

Interesting, didn't know that. I've only owned F series FL and FD mount cameras, and a T60. No A series!

 

[David Goldfarb]

Sometimes the meter (any in camera meter) can be non-linear in low light, and when you shoot in stopped-down mode, it's more likely to be low light from the perspective of the meter, so you often get a more accurate reading by metering at full aperture.

You might try comparing readings at full aperture vs. stopped down outdoors in full daylight and indoors, and at wide and at smaller apertures to figure out when stopped down metering is likely to be unreliable.

 

[Gid]

Check out http://www.canonfd.com/choose.htm Hopefully you will find what you want there.

 

[Paul Connet]

Specifically the Canon A1, or something similar. It seems to me that, using stop down metering, the camera selects a slower shutter speed than if using aperture priority. Am I doing something wrong?

I just checked my A-1 with a 50mmf1.4, and at all f-stops except f1.4 it operates as it should, giving the same shutter speed in stop-down that it gives in aperture priority. With the lens set to f1.4 in stop-down mode the shutter speed is about half what it should be. Seems peculiar except that at full aperture there is no reason to use the stop-down button anyway.

Regards, Paul C.