35-105/3.5 aperture

my only bayonet fd lens, which is a 35-105/3.5 (new FD?) displays the following

behaviour. When mounted on an Ftb body the lens is completely open only when

actually set to 3.5, otherwise it closes to about 5.6 and stays there, e.g. if

I chose f/11 the aperture closes to about 5.6 and then when the actual exposure

is being made closes to f/11 as it should, then snaps open back to 5.6. When

the lens is set to 3.5 then it actually opens all the way to 3.5. Also I found

that should I use the dof lever the lens remains closed even when the lever is

moved back to the open aperture metering position, and I have to turn the

aperture ring back to 3.5 to open it. It does not snap open the way all of my

breech lock FD lenses do. I tried it on all of my Ftb/Ftb(n) bodies and it's

the same.<p> I find this rather puzzling, but I also wonder if perhaps it's

normal for non-breech lock lenses. And, yes, the blades are clean and dry, I

don't see any oil or obviously bent or otherwise constricted levers etc. also I

am aware that when NOT mounted on a camera the diaphragm should be closed to

about 5.6. If anyone has any hints on how to take it apart, I'd appreciate

hearing about it too as perhaps there's some internal problemme. <p>

Hi Zenit,

 

Are you sure the lens is fully mounted, i.e., the chrome lens mount release button snapped into place? Normally, as you mount a new FD lens, the partially closed aperture should open up as you turn the lens, and becomes fully opened when the button locks. I mounted my 35-105/3.5 on one of my FTbN bodies and the aperture was wide open.

 

When you mount the lens, does the aperture open up as you turn it?

 

Gordon

Zenit, I was curious about this, so I stuck mine on an F-1N body. It behaved differently from your lens. The iris diaphragm remained wide open when it was mounted on the camera, irrespective of what the set aperture was on the aperture ring. This is what you'd expect for any FD lens, so I suspect your diaphragm is sticky and needs a cleaning.

 

Do you notice overexposure at the small apertures? If your TTL meter is reading through f/5.6 but thinks it's at full aperture f/3.5, it will tell you to give a little over twice the ideal exposure. This would be more of an issue with slide film than with negs, and maybe you don't use the onboard meter anyway.

Zenit, Same lens on my FTb is at 3.5 when mounted regardless of where the ring is set. When the shutter closes, the aperture stops down to wherever the ring is set. With the DOF lever in, the aperture opens and closes f22 to f3.5 with the ring. Does it work the same way on non FTb bodies?

Some non-Canon users, and even some Canon users, think of the new FD design as a change in the lens mount. While the mechanical aspects of mounting a lens changed, the FD mount remained totally unchanged from a functionality standpoint. Any FD lens, whether a first generation chrome nose from 1971 or a new FD lens from the late 1980s, is fully functional on any FD mount body, with no modification or adjustment needed. I'm still impressed with the forethought and planning of the Canon designers and engineers.

 

Whether it's an old or new FD lens, it must be mounted so that the lens' aperture signal lever (the smaller lever on the back of the lens) is fully engaged. With breech ring lenses, this usually isn't a problem because the lever engages well before the mount is tight. With new FD lenses, the lever should be engaged when you hear the reassuring "click" of the chrome release button as it lock in place.

 

Zenit, I hope that the problem is simply that your lens was not fully mounted.

Gordon, no unfortunately it's not as simple as not mounting the lens properly. It clicks in and the blades open to 5.6 unless the aperture ring is set to 3.5 in which case it does open all the way.<p>

I set the camera on B-lock and looked through the back as well as the front while turning the aperture ring back and forth--the blades are clean, not a trace of oil. I suspect that something inside must have been bent or misaligned. <p>

Dave, I thought about the "open aperture" metering as well, here's some data: zoom set at 50mm (vs 50/1.4ssc). At 1/15 6.3(vs 8), @1/60 3.5 (va 4), @1/4 13 (vs 16). Hence it's consistently +0.5EV, not +1.5 as one would expect. Thus once again I suspect that the problemme is deeper, perhaps with the way the aperture actuator couples to the iris mechanism. <p> Tim, thanks for letting me know how it supposed to be. I only have Ftb bodies as I feel that that's the model which has all of the features I want and none of the battery sucking gizmometry that I don't really need. It'd be interesting though to put it on a body that supports the A setting and see what comes out of it. <p> I mostly bought this lens since I have a Pentax-A 35-105/3.5 and use it a lot. I wanted to get a Canon equivalent. Overall canon's version is a lot flimsier, too much plastic and the macro feature is a joke. I do enjoy my old Canon primes though.

Sorry, Zenit, it sounds like you do have a problem. It may not be relevant, but Canon made two different 35-105mm zooms in the new FD mount. It sounds like yours may be the push-pull zoom with the variable aperture (f/3.5 at 35mm, f/4.5 at 105mm). This was an inexpensive lens that was bundled with T-series bodies. The other lens was a high quality, metal barrel two-ring zoom with a constant f/3.5 aperture. This is the lens that I have.

no, mine is a constant 3.5 version as well, Gordon. 72mm filtre, two ring zoom/focus. The front however made is of plastic. That's ok, I mainly wanted to ascertain that it is supposed to be functioning as one would expect on my cameras. Thanks for all of your help.

Hello Zenit,

I am new to the forum and I am an amateur-just getting my hands dirty. I believe I have stumbled along a similar problem with my 35mm f/2 SSC lens; however, it is a breech lock mount. My aperture is not opening fully for any positions after the shot; in other words it is not snapping open either-which is what I expected. I bought it used from ebay, but since I cant figure out what exactly is wrong nor how much it will cost to fix(not sure if it just needs cleaned or what)-I am resigning to send it back to the seller. Just wanted to let you know, that your not the only one with this kind of prob.