Canon FTb QL aperture mysteriously only works with one lens

I recently bought a Canon FTb QL for a steal ($15 or so), but am having problems with it. I own three Canon FD lenses of the twist type, a 28 f/2.8, 50 f/3.5 macro, and 35-70 f/4. Curiously enough, the camera's match-needle aperture needle (the round "lollipop" one) only works (moves) with the 50mm macro. While a great lens, I would like to use my other lenses on this body. I know that the camera body's not totally broken, since it works with the 50. I know that the 28 and 35-70 are not totally broken, because their apertures work when connected to my NEX (does this mention count as "digital content"?) adapter. I'm truly confounded -- can anyone help?

I can post pictures of mechanisms on request.

Thanks.

By "twist" do you mean breech lock? The old lenses had a "lock" setting that would override the stop down mechanism of the body
Sometimes the actually said lock and sometimes not.

John Koehrer said:

By "twist" do you mean breech lock? The old lenses had a "lock" setting that would override the stop down mechanism of the body
Sometimes the actually said lock and sometimes not.

Click to expand...

I mean the newer FD twist-and-lock, not the breech-mount. The one with a more modern design, where you twist the lens onto your body and it clicks into place, and you press the small silver button to release it.

Check your lenses, some will mount when set to the green "A' or Bullseye dot on the FTb but won't couple to the meter.

This is a picture of the outside thing that I know can mess with aperture settings. It's on the white circle.


These are the backs of the lenses in question: on the left, a 50mm f/3.5 macro, which works with the body; on the right, a 28mm f/2.8, which does not work. To my untrained eye, these mechanisms look the exact same, other than that the 28's seem to have gaps under the silver things while the 50's mechanism has full, silver-colored bars.


I set the 50 to f/8...

... and the lollipop moves! Just like it's supposed to.

Now, with the 28 on the body:

It's set to f/5.6...

And yet the viewfinder lollipop is set as if the lens is at 2.8.

I hope that some of the images illuminate the problem. Thank you.

Set the camera to a slow shutter speed - say 1/2 sec. Mount the offending lens and try tripping the shutter at different apertures.
Does the lens close down to the set aperture size?
If all is functioning correctly here, then the problem might be with the linkage in the camera that engages the match needle (lolipop)
T

Toyo said:

Set the camera to a slow shutter speed - say 1/2 sec. Mount the offending lens and try tripping the shutter at different apertures.
Does the lens close down to the set aperture size?
If all is functioning correctly here, then the problem might be with the linkage in the camera that engages the match needle (lolipop)
T

Click to expand...

I tried it, and the aperture does not stop down with the 28mm lens.

The lube in FDn lenses breaks down over time. What you end up with is oily blades, they're stuck to the
blade housing. it's possible to rotate the silver ring at the lens mount and that would allow you to stop it down
when it's not on the camera.
When I serviced these I used the lens mount from a parts camera to check this when we had a lens with the same complaint.

John Koehrer said:

The lube in FDn lenses breaks down over time. What you end up with is oily blades, they're stuck to the
blade housing. it's possible to rotate the silver ring at the lens mount and that would allow you to stop it down
when it's not on the camera.
When I serviced these I used the lens mount from a parts camera to check this when we had a lens with the same complaint.

Click to expand...

I don't think that the aperture blades are stuck, because every lens in question works on an FD-NEX adapter, including aperture.

Ibynx said:

These are the backs of the lenses in question: on the left, a 50mm f/3.5 macro, which works with the body; on the right, a 28mm f/2.8, which does not work. To my untrained eye, these mechanisms look the exact same, other than that the 28's seem to have gaps under the silver things while the 50's mechanism has full, silver-colored bars.

Click to expand...

To me it looks like the lens on the left has 2 aperture levers and the one on the right has one.
The lens on the right aperture lever appears to be shorter than the lever on the lens on the left.
Use a fine graduation ruler and measure the aperture lever height from the lens back, all lens of this type should be the same, if not check that the lever is not pushed in.
Also check that the body aperture lever is not bent or pushed in from improper lens attachment/attempt.

Just my observations from reading the thread several times.

shutterfinger said:

To me it looks like the lens on the left has 2 aperture levers and the one on the right has one.
The lens on the right aperture lever appears to be shorter than the lever on the lens on the left.
Use a fine graduation ruler and measure the aperture lever height from the lens back, all lens of this type should be the same, if not check that the lever is not pushed in.
Also check that the body aperture lever is not bent or pushed in from improper lens attachment/attempt.

Just my observations from reading the thread several times.

Click to expand...

While the aperture levers are the same height and length on both lenses, I found something interesting while checking it. On the lens on the left (the 50 macro, which works), the large aperture lever, when pushed on its track, locks at the very end of the track. However, on the non-working lens (on the right, the 28), the lever does not move the entire length of the track (stopping about halfway), and does not lock in any position, just springs back to the original. Does anything stick out there?

Ibynx said:

on the non-working lens (on the right, the 28), the lever does not move the entire length of the track (stopping about halfway), and does not lock in any position, just springs back to the original

Click to expand...

See post #8.