[waddojohn]

Hi

Any answer to my problem.

I have a Pentax K10D that has developed a problem, when looking through the viewfinder with the lens on A-Lock the view is dark. I can change the Mode Dial to anything this does not change the view, or when I change the ISO to 1600, I cant get the speed above 1s
the view becomes bright when the A-lock is disengaged

I have tried the Sigma 50-500mm on another camera,
eg. AV f6.7 1/60 ISO 800 on the Pentax ist DS time 15:43
same settings on the K10D AV f13 1s ISO 800 time 1600

noticed the problem Jan03 2011

Thanking you for all your Help

Regards

John

[Ash]

John - by A-lock, I assume you mean the Auto aperture setting on the lens's aperture ring.
If so, when properly mounting the lens in A-mode, the diaphragm should automatically open up to permit full light passage through the lens for the viewfinder, and only stop down when the shutter is released.

I don't quite get the trial you put the lens through on the other camera, but is the problem replicated on the *ist DS or not? (I don't suspect so).

Try unmounting the lens, cleaning the mounts on both the lens and camera, then mounting firmly again. If the problem still exists I wonder whether the aperture lever on the K10D is faulty - not opening up the diaphragm (see at about 9 o'clock on this image of the K10D mount).

[SOldBear]

John,

I don't fully understand your description of the problem. So I have a question:

Attach a lens that has an aperture ring to the K10D (manual lens is OK). Look straight into the lens. Rotate the aperture ring. Do you see the aperture blades of the lens closing and opening?

Normally the lens aperture is fully open, and you should not see the aperture blades closing and opening.

If you do, I think I know what the problem is and the fix may be simple. I just need to do a bit of digging.

Please post back.

[JeffJS]

+2 on both responses.

Put the lens on the camera, hold the camera so you are looking through the lens from the front while pointing the viewfinder at a light source. You should be able to see through the lens if the aperture is open or not. This will be true regardless of the A setting on the lens. If you cannot, then either the lens aperture is not working (simple to check by flicking the lever on the rear of the lens mount to see if it opens and closes) or the camera's aperture coupling has gone south (assuming the electronic coupling is complete). Mode, ISO, Shutter speed etc will not matter until you take a photo (or it shouldn't).

[waddojohn]

Hi Guys
Sorry about the too much info, "panic writting"
Thanks for the quick responce, The test was for me to eliminate the Sigma 50-500mm as I had it serviced before Christmas and it works fine on the istDS. never thought about the K10D being at fault at that time its been rock solid.
"Habit of cleaning contacts everytime I switch lens's."
Tried the putting a couple of lens on this morning before setting off to work.

aperture lock on, you get a reading F stop and speed, the blades are visible, using the pre aperture lever you can hear the mech working but No movement of the blades.
aperture lock off, Reading shows F--- and a speed, blades again visable and by turning the aperture ring the diaphragm opens and closes at each f-stop, again you hear the mech working but it doesnt open up the diaphragm to its widest opening on any of the f-stops.

Best Regards

John

(I'd noticed someting was wrong when I had tried to take a Bittern in flight that had appeared out of the reeds, all I got was a brown smudge, the previous shot was an amazing shot of a water rail, never seen one that close, possibly due to the lake being frozen at the time)

[SOldBear]

OK, John. Don't panic. I think the fix is simple.

Remove the lens, look at the camera body lens mount, at 9 o'clock position. There is a little black lever (tip of arrow in photo below). Let's call it the actuator (I'm not sure that's the official name). It is normally in the "down" position.

Activate the DOF review (the power switch around the shutter release button). Normally you should see the actuator moving up and down. In your case, it probably doesn't. (Note that for newer DSLRs, e.g. K7, this actuator normally does not move if there is no lens attached to the body).

Use a pointy object (a tip of a test probe, or a tip of a ballpoint pen), try to push the actuator up gently. Normally you should feel the resistance of a spring. In your case, there is probably no resistance at all.

What happens is that there is a spring attached to the lower end of the actuator, pulling the actuator down (thus opening up the lens's aperture). In your case, for some reason, the spring has detached from the actuator.

To re-attach the spring, activate the DOF review to expose the upper end of the spring, then use a tip of a test probe (or a good pair of tweezers or a metal paper clip) to push the end of the spring up and to convince the spring to hook onto the little protrusion at the lower end of the actuator. Make sure NOT to use anything that can break - you don't want another problem

Don't curse at Pentax engineers for the "lousy" job of designing this mechanism. I think it's a good design. When the lens's aperture mechanism gets stuck, something's got to give. It is easier and less costly to re-hook the spring than to replace a broken part.

Good luck, and please post back.

[waddojohn]

Hi SoldBear,

I can see what your pointing at, When I switch on and move the Depth of Field lever, can hear the noise and there is no movement in the slide, the black lever is at the top (black lever one at each end)., it will only move down. so the spring must still be attached at the bottom end.

Regards

John

[Ash]

The DoF preview should make the lever move.
Does the lever spring back to position when physically manipulated?

[waddojohn]

Hi Ash,

Yes it does springs back up when pushed down, physically manipulated. not by the DOF switch. (you can hear and see the cog action when the DOF switch is actioned)

Regards

John

[JeffJS]

For what it's worth, the preview does nothing on my K5 when no lens is mounted. The actuator inside the mirror box can be manually manipulated and snaps back just like you are reporting on your K10d. With the lens mounted, you should be able to watch the aperture operate when operating the Optical Preview.

[waddojohn]

I cannot see a clear view with a lens mounted through the viewfinder, could be that the aperture lever has a problem with the depth of field action. the lens blades are normaly at their widest when you put a lens on and you can preview by using the depth of field lever.
I cannot get the diaphram to move by using the DOF lever. In the picture that is supplied by Ash and SOldbear, it shows where the lever should be. mine is at the top and not as show in the picture.

It seems my only option is to take to a good repairshop, armed with the knowledge you kind people have given me.
Regards
John

[JeffJS]

I cannot see a clear view with a lens mounted through the viewfinder, could be that the aperture lever has a problem with the depth of field action. the lens blades are normaly at their widest when you put a lens on and you can preview by using the depth of field lever.
I cannot get the diaphram to move by using the DOF lever. In the picture that is supplied by Ash and SOldbear, it shows where the lever should be. mine is at the top and not as show in the picture.

It seems my only option is to take to a good repairshop, armed with the knowledge you kind people have given me.
Regards
John

Look at it from the Front holding the camera so that light shines through the viewfinder. You Did set the camera for Optical Preview, correct?

[waddojohn]

Hi Guys,
I sent all the information given on here to Pentax support UK. this is what they said.

Sounds like an Aperture block problem. your iris blades are not being opened when you attach your lens giving you a dark picture through the view finder.

A lot wiser with all your Help,

Many Thanks

Regards

John

[SOldBear]

For what it's worth, the preview does nothing on my K5 when no lens is mounted.

That's correct. Pentax changed the firmware some time back, I think right after the K20D. Among other things, the DoF review does nothing if the body does not detect a lens attached. I mentioned in my previous post:

...(Note that for newer DSLRs, e.g. K7, this actuator normally does not move if there is no lens attached to the body).

Back to the original problem....

To me at this point, it's pretty obvious that the problem is that the bottom spring has been disengaged from the hook.

All the symptoms match:

When I switch on and move the Depth of Field lever, can hear the noise and there is no movement in the slide, the black lever is at the top (black lever one at each end).

Normally the actuator is at the "down" position (see photo in my previous post). Because the spring has been unhooked, there is nothing to keep the actuator down.

...it will only move down. so the spring must still be attached at the bottom end.

If the spring was still "attached at the bottom end," the actuator would be at the down position already. How could it "only move down"?

Yes it does springs back up when pushed down, physically manipulated. not by the DOF switch. (you can hear and see the cog action when the DOF switch is actioned)

Another symptom showing the bottom spring has been unhooked.

I cannot see a clear view with a lens mounted through the viewfinder, could be that the aperture lever has a problem with the depth of field action. the lens blades are normaly at their widest when you put a lens on and you can preview by using the depth of field lever.
I cannot get the diaphram to move by using the DOF lever. In the picture that is supplied by Ash and SOldbear, it shows where the lever should be. mine is at the top and not as show in the picture.

You just verified the cause of the problem.

Have you attempted to re-hook the spring as described in my post above? Or at least, have you verified visually whether the spring is still attached to the actuator?

"To re-attach the spring, activate the DOF review to expose the upper end of the spring, then use a tip of a test probe (or a good pair of tweezers or a metal paper clip) to push the end of the spring up and to convince the spring to hook onto the little protrusion at the lower end of the actuator. Make sure NOT to use anything that can break - you don't want another problem."

[Ash]

Indeed, if SOldbear's advice is followed you may not need to send your camera to the repair shop.
Let us know how you go with it.