How aperture works on Sears AUTO 135mm F:2.8 Macro?

[igor_kernes]

Hi.

I try to decide if this lens works properly.

Diaphragm blades on my copy always wide open and I can't step down

manually. On another hand K100D cannot control aperture neither. Do I have

broken copy??

[mc2imaging]

Is this a K-Mount lens (versus an M42 screw mount)?

 

Does it have an 'A' on the aperture ring?

 

Assuming it is a K-Mount 'Auto', the aperture will be wide open when on the camera,

but when off the camera the aperture should close and open when turning the ring.

The camera stops down the lens during shutter actuation.

 

The K100D can only control the aperture if the ring on the lens is set to 'A'.

[igor_kernes]

It is PK-Mount, no A on aperture ring. Off the camera lens do not respons when turning ring.

[tommyinca]

The aperture iris of K-mount lens close with the aperture ring when detached from the carmera. If yours doesn't, you have a stuck aperture iris which likly caused by oil on the iris blade. Not a easy problem and expensive to fix.

[leicaglow]

Does it have a pin on the back face of the lens mount that closes the aperture when pressed into the lens?

[kenneth_peters]

Here is a photo of the rear of that lens. Compare to the typical PK mount with "A" setting. Quite different. I have one also, and I cannot get the K10d to stop the aperture down in any setting. The lens does stop down on a Pentax ZX-M.

 

Groetjes,

Ken<div></div>

[jeffpolaski]

Follow the many posted instructions on using pre-digital manual lenses on Pentax DSLRs. The lens is actually quite a good performer despite the label.

[azemerov]

Rotation of aperture ring doesn't open/close the aperture - it's only sets the stop position. You have to move the lever to see aperture in action<br>

So, first, set 1/16 aperture and check if aperture closes when you shift lever on unmounted lens. If it opens and closes iris easily - lens is fine.<br>

Second, you have to enable usage of old lenses with non-A setting in the menu.<br>

Third, to use step-down metering with such old lenses you should set aperture value on the lens and press AE-L button (on K100D body, not sure about K10D, check with documentation). Don't forget to set the "M" exposure mode.

[jemal.yarbrough]

I have that lens. Make sure your camera is set to use a manual lens that doesn't have an A setting. If you change the aperture of camera, you should be able to push the lever on the back and see the step down occur. Nothing will happen if the lens is at its widest. Good luck.

[igor_kernes]

No. It does not have any pin<div></div>

[igor_kernes]

I try to set different F numers and move lever on lens off camera -nothing (diaphragm did'n react)... .