I have a Pentax istD body with a Sigma 105mm macro lens. Its probably 12 to 15 yrs old. Use it for dental photography and have multiple staff using the camera. Suddenly the viewfinder went darker than normal. You can still see through the viewfinder but it isn't very clear. I have the setting on the camera at Auto. When I switch to manual and open and close the F stop I can see through the viewfinder more clearly as I open the lens. I tried to clean off the contacts between the lens and the body. I have another sigma lens for the camera and it did it with that one too. Any ideas what is going on and if it is time for a new camera or is there a simple repair?

[UncleVanya]

Looking at the front of the lens does it look like the aperture is wide open while the aperture ring is locked into the A position? If not the aperture lever may be bent and not properly making contact when you mount the lens on the camera.

Do you have any Pentax lenses and are they working correctly?

The aperature is not wide open. When I play with the lever arm it still clicks it open and closed. How do I try to bend the arm to the right position. Thanks!

[UncleVanya]

The aperature is not wide open. When I play with the lever arm it still clicks it open and closed. How do I try to bend the arm to the right position. Thanks!

Bending is just one way it could be wrong. Does it look bent? Is the body lever bent? You need the lever in the body to catch the one on the lenses. If two lenses are both not working I’d start by looking at some pictures of the body mount and making sure the lever looks correct.

It does not look like the lever is bent on the lens. It clearly opens and closes the aperture when I move the lever with my finger. I looked at where the lens lever arm connects to the body. I saw the little part that moves up and down and it seems to move smoothly. Not sure how to tell if it is bent. I cleaned some black residue junk out with a clean pencil eraser. It looked like it made the viewfinder a little better. Then I took a picture and it went back to being darker again??

[swanlefitte]

My 55-300 PLM does this occasionally also and it doesn't even have an aperture lever. I have to assume one or more aperture blades catches somehow.

If it only happens with one lens and that lens has a snappy lever when you manually flip it, it is probably inside the lens. It could be grime, loose blades, or just wear. I assume with mine that a blade will lift slightly or something inside moves around as the blades move and occasionally prevents the blades from fully opening.

[UncleVanya]

My 55-300 PLM does this occasionally also and it doesn't even have an aperture lever. I have to assume one or more aperture blades catches somehow.

If it only happens with one lens and that lens has a snappy lever when you manually flip it, it is probably inside the lens. It could be grime, loose blades, or just wear. I assume with mine that a blade will lift slightly or something inside moves around as the blades move and occasionally prevents the blades from fully opening.

Two lenses. Both 3rd party.

To be dark during viewfinder use suggests excessive friction or a misalignment in the levers or total failure of the aperture control system in an unusual way (locked in the closed position all the time not just during an exposure.

---------- Post added 11-07-22 at 03:16 PM ----------

This may help diagnose things.

Aperture lever engagement of Pentax lenses. by -vanya_42nd-

Well.... I think you have definantely found the problem part but I'm not sure how to fix it?? Would a picture help you figure out more? If so how can I attach a photo?? Maybe it is not repairable..There is no one around my area who could repair it so maybe time to just get a new camera?

[UncleVanya]

Well.... I think you have definantely found the problem part but I'm not sure how to fix it?? Would a picture help you figure out more? If so how can I attach a photo?? Maybe it is not repairable..There is no one around my area who could repair it so maybe time to just get a new camera?

Does it look like what I showed? Or different?

As far as images you can attach one potentially but you can also use a photo sharing site like Flickr and post the BBCODE link here.

The picture you sent looks different than my camera. Mine only has one lever and your appers to have two. The best I can tell mine has the smaller lever, it is made of black plastic instead of the silver look of yours and mine is missing the larger lever. This lever does slide up and down easily with finger pressure.

[UncleVanya]

The picture you sent looks different than my camera. Mine only has one lever and your appers to have two. The best I can tell mine has the smaller lever, it is made of black plastic instead of the silver look of yours and mine is missing the larger lever. This lever does slide up and down easily with finger pressure.

Mine has one but it looks to be made of two pieces. The k100D image later shows a single black piece. It shouldn’t move when the system is powered off as far as I know. I’m guessing the linkages inside the body are broken or disconnected. I’d say it’s time to look for a replacement unless you are planning a self repair effort.

Thanks for all your time and effort to help me with this. I like to try and fix things but this one is over my head so time for a new set up.

[pschlute]

Thanks for all your time and effort to help me with this. I like to try and fix things but this one is over my head so time for a new set up.

You would be very welcome to sign up for a forum membership (costs nothing). Then you can post in all the forums available here.

As much as you may learn from us here, we may learn from your creativity too.

[Pentax4me]

Could it be possible that an inexperienced staff member changed lenses without knowing how to do it properly and bent the lever on the camera? I’d suggest a strict policy of lenses being changed by you and nobody else, unless you are very satisfied that they know what they’re doing.