[SteveNunez]

Hey guys, I bought a mint Vivitar 75-205 f3.8 Mc lens and when I mount it on the K1 the aperture won't change but if I start to twist the lens off the body slightly, the aperture works (and works off the camera as well) it just won't change aperture when fully mounted- has anyone faced this- what was the remedy?
(I can't use it when it's not in the locked position as it can easily fall off- so using it this way doesn't seem like an option.)

I'm guessing the little lever that controls the aperture is slightly off- can this be fixed by myself?

The optics are flawless and I really want to use this lens as it has great reviews- what do you guys think?

Thanks in advance for any replies.

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Last edited by SteveNunez; 12-16-2019 at 05:22 PM.

[Not a Number]

The problem is that the lens appears to be a K mount, not KA or later with electrical contacts. As such the lens will only stop down in manual mode when taking an exposure or operating optical DOF preview.

I suggest you review the following two threads:
Manual Metering on Pentax DSLRs with Manual and Automatic Lenses - PentaxForums.com
How to use/meter Manual & M42 Lenses on all Pentax DSLRs (K-1, K-3, K-5, K-30, etc) - PentaxForums.com

[k0og]

Steve,

It's a little hard to tell with the angles of the pictures you posted, but it does appear that the aperture tab is a little bent. I suppose that could be a problem.

What Not-A-Number suggested is well-worth your reading. In M mode, using the "green" button to set stop-down exposure prior to taking the picture, this lens should work fine. I have one of those, and it is optically VERY good in my opinion!

-Joe-

[SteveNunez]

Thanks guys but I believe you’re not understanding the issue.

The issue is the lens aperture is adjustable when mot mounted on the camera. When the lens is mounted and locked into position I cannot change the aperture- it remains wide open. If I start to remove the lens and twist slightly to remove I can then control aperture- that’s the issue at the moment.

I’m no Pentax expert and was hoping the included photos might show what the issue is: if anyone has any ideas why this is happening or how I might address it, I’d love to hear it.

Thanks again guys for the replies- hopefully I’ve explained the issue a bit clearer.

[Just1MoreDave]

All K-mount lenses will have a wide-open aperture when they are fully mounted on the camera. The camera has an aperture arm that shoves the lens's lever as it's twisted on to open the blades. Watch the blades as you mount a lens: unless it has an aperture ring already set to wide open, the blades disappear. That's to make the viewfinder bright for easy focusing.

Lenses with an aperture ring and no A position on the ring will always shoot wide open on a Pentax DSLR except if the camera is in M mode and the custom setting for using the aperture ring is enabled. When you do those things, the camera will stop down the lens to the aperture ring setting when you shoot, and to meter, usually by pressing the green button.

[peggers]

All K-mount lenses will have a wide-open aperture when they are fully mounted on the camera. The camera has an aperture arm that shoves the lens's lever as it's twisted on to open the blades. Watch the blades as you mount a lens: unless it has an aperture ring already set to wide open, the blades disappear. That's to make the viewfinder bright for easy focusing.

Lenses with an aperture ring and no A position on the ring will always shoot wide open on a Pentax DSLR except if the camera is in M mode and the custom setting for using the aperture ring is enabled. When you do those things, the camera will stop down the lens to the aperture ring setting when you shoot, and to meter, usually by pressing the green button.

The green button is awesome! Does anyone know if this green button or similar is exclusive to Pentax? I suspect it is but am curious.

[SteveNunez]

Thank you guys, I did as S RE E suggested and it works....thank you.
I thought when in M mode I would have to rotate the aperture ring and didn't know the camera would be used to control aperture.....still learning- thanks again everyone.

Cheers~