# Canon AE-1 + FD lenses. F-stop doesn't affect light meter?



## ghosteater (Apr 11, 2012)

Hey - apologies if this is an obvious question - I am new to this....

I am using old manual FD lenses on a Canon AE-1. My issue is > The light meter only changes when I change the shutter speed... it doesn't move when I change the aperture (the aperture it seems to always read as wide open). To me that seems silly.... why would an F2.8 @ 60 shot have the same metering as an f16@ 60 shot (there would be a totally different amount of light coming in)?

I was using the DOF preview button, and that made it so changing the f-stop actually affected the TTL metering like the shutter speed does - which seemed right.... but I then read online that you should never use the DOF button for metering, or leave it pushed in, as it will give an incorrect metering since the metering was 'made to be used with the lens right open to allow for the most light' etc. 

I can't imagine this is right. Unless it's like everybody knows you 'only use the TTL metering for the shutter and then do some mental calculation to figure out how various stops down affect the light coming in' or something weird (which seems really weird)?

This behavior happens with all 3 of my FD lenses... so is something wrong with my camera? Or is this some behavior that is typical of the FD lenses or AE-1 w/FD lenses? I know I use them (adapted) on my video camera sometimes and they can be a pain in the ass to get manual aperture on. Is there some pin on them that needs to be pushed in or something? I think I saw some post alluding to having to 'reset' them (going from biggest to smallest f-stop twice or something) - does that have something to do with it? Thanks so much!


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## ghosteater (Apr 11, 2012)

(ps - is it maybe something about the FD lens being locked? like maybe the DOF button being pushed was freeing up the aperture ring? would doing this http://i97.photobucket.com/albums/l203/splifteam/FD.jpg - I'll wait before doing it and messing anything up ;P  )


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## ghosteater (Apr 11, 2012)

I just looked down the lens with the aperture on f2.8 with a 2 second shutter took a picture (saw the shutter was wide open), and then at f16 with a 2 second shutter (saw the shutter was stopped down) - so there is a difference - the aperture does change for the final picture... so it just doesn't change when metering. it changes right before taking a pic.. and does not affect the metering. that can't be right?


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## Mot (Apr 11, 2012)

The AE-1 is only a shutter priority camera. The only time the camera is in a program/automatic mode is when the aperture dial is set to 'A' meaning your only control when metering is shutter speed. By adjusting the aperture ring away from 'A' you are effectively switching the camera to manual mode, you'll get the flashing 'M' in the viewfinder. The meter will still work based on your shutter speed but you'll have to set the aperture manually.

This isn't really a problem, you can adjust your shutter speed so the dial matches your desired aperture even when in shutter priority.

If you were using a Nikon camera you'd find the opposite. A lot of older Nikon cameras were aperture priorityy so you'd only be able to meter by adjusting aperture, not shutter speed.

I hope this helps.


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## unpopular (Apr 12, 2012)

On older lenses, there will be a FL-mode lever on the back which will force the lens to stop down when the aperture ring is changed. Be aware that this will cause the viewfinder to dim, but the meter will read 100% accurate at a given exposure time. I have come to appreciate stop-down metering, but it's not for everyone.


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## TCampbell (Apr 14, 2012)

An AE-1's built in light met ONLY reports the recommended aperture... based on the ISO set and the shutter speed currently selected.  If you set the aperture ring on the lens to "A" then the camera will set that aperture for you.  Otherwise it's up to you to manually set the exposure.  Changing the f-stop on the aperture ring isn't supposed to affect the meter on that camera.  Your camera is working as intended.


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