F 50mm macro clamp question

Hey folks.

Picked up a reasonable FA 50mm Macro but the focus clamp seems very loose and doesn't affect anything. AF is fine and the price was less than £100.

Is it worth bothering getting it repaired or should I just return it.
What's the reduction in value? Roughly.

Any views gratefully received.

Thanks

It was the same on my 100mm, as far as I was aware it's used in manual focus to tighten up the focus ring slightly to either keep the focus point locked or the make the focus ring tighter.
I was told it comes loose if you set the switch to the on position whilst using autofocus and also damaging the lens in the long run.
I must admit I never used it and was always turned off, have you tried it yet in the on position, whilst in MF and the switch turned to on the focus ring should either be locked or a lot harder to turn, if neither happen it looks like it's been damaged.

Thanks Matty,

No difference, it feels loose and doesn't seem to tighten as you close the clamp. Also when closed the manual focus seems as easy to turn with no discernible change.

I'm guessing the thing is broken.

However it works fine as a 1:1 AF Macro so I'm not unhappy.

Thanks

No problem, Never missed it from the day I bought it to when it was sold on, I have now seen quite a few like this, so I am guessing it's just down to a weak part.

Just bought a Pentax smc DFA 50mm f/2.8 Macro Lens via Amazon.

The Clamp switch disables AF when set to ON (as expected) but there is virtually no difference in focus ring friction between ON and OFF.

The focus ring friction feels about right to me for manual focus. However, there is a little bit of frictionless backlash (i.e. when rocking the focus ring).

Initial macro results I would describe as less than super-sharp.

Reading several posts, it looks like the friction varies from "almost none" to "cannot turn" for other samples of this lens.

Do you think I've been sold a donkey?

The clamp is purely there to stop any focus shift in manual focussing mode, especially in circumstances where gravity might play a part, i.e. if using a copy stand so the lens is pointing straight down.

Set to manual focus, adjust focus, switch clamp 'on' to hold focus. That's it.

DON'T try to change focus when the clamp is 'on'.