Exposure problems using my old vivitar lenses on my K10

I recently bought a K10. One reason for this was to use my lenses I bought for my mesuper.
The problem I have is that the pictures are always over exposed when using my vivitar zoom lenses. My pentax lenses seem to work fine. The lenses are manual ones.

I have noticed that the lever on the K mount that operates the iris appears to be 'damped' on the vivitars, but work much quicker for example on my pentax-m 1:1.7 50mm.

I suspect my K10 is taking the picture whilst my vivitar lenses are still stopping down. Anyone having the same problem ? Any solution besides only using the lense fully open, which of course works fine.

Hi TR,
Welcome to the forum. The issue of overexposing regarding the K10D is well discussed over here. There are 2 solutions for the problem. (AFAIK)
1# replace the focusing screen for one used in older models. (not sure which one ) could be the k100 or previous model.
2# only use manual focus A lenses. These have the necessary electric contacts and give you everything except Af. The latter is most advised.
HIH,
Martin.

Thanks Martin,

I've read the other posts about the metering system not working very well as the lens is stopped down, but my fault is a greater error than that and I believe the vivitar lenses arn't stopping down in time ans are still in the process of stopping when the camer is taking the shot.

ie what I think I have is a lens fault, not a camera fault... sort of... well, I don't think the camera and lens are singing from the same hymn sheet !!

Oil on the aperture blades?

Thanks Pete,

could be, but I've never had the lenses in bits. As far as I know they are working the same as they have ever done. Having said that, they haven't been used for a few years !!!
I have been 'flicking' the iris to see if Icould loosen it up a bit...

I notice exposure variation with some of my lenses. I suspect it's usually because the apertures are not always the size they are supposed to be.

You could compare depth-of-field with a good lens - if you suspect the Vivitar is not stopping down anything like enough before the shutter fires.

You can test the condition of the aperture ,echanism by taking off the lens and flicking the stop down lever on the mount. It should be snappy and resposive. Any sluggishness in operation will mean exposure errors.

Don't forhet to set a small aperture to test as at open aperture it doesn't stop down at all....

The vivitar lens stops down OK when the green button is pressed and also when the preview lever is actuated. I believe the iris is slow in stepping down and does not achieve the correct position before the shutter fires. My Vivitar lenses are the 28 - 90 series 1, and the 70 -210 series 1.

Anyone else had similar problems ?

If you have oil on your iris blades, you'll be able to see it very easily. With lens in hand, select the smallest aperture and operate the stop down lever if necessary to close the iris.
Inspect both sides of the iris. If it looks at all wet, you have oil on your blades and they'll need a service to fix the problem.

I have examined the iris on each lens and can't see any sign of oil. Operating the iris by the lever in the mount shows the action to be sluggish. I don't know if this is normal for these lenses or not

As already mentioned, the stop down action should be crisp and snappy. Sluggish is no good and needs repair. Unfortunately this is very unlikely to be cost effective.

You could still use them with the 2 second delay, the lens shuts down when the timer starts so it should give it plenty of time to reach the right aperture before firing the shutter. Not exactly a perfect solution but as long as you're not shooting action then it's better than nothing...

I've just done a quick test. Took a picture of the garden with my vivitar set at full apature - perfect
stopped down to minimum, pressed green button, shot again, - under exposed
switched 2 sec delay on, everything else same - perfect again

I think this proves it's an apature fault, but at least I have a work around now by using the delay function.

Did you mean under exposed? That would imply that the set aperture is too small and that the iris is stopping down ok. If it wasn't stopping down far enough, your images would be over exposed.

If you meant over exposed, then there would seem to be an issue somewhere.

Yes, sorry, brain fade...

on minimum apature the photo was over exposed untill the 2 sec delay was initiated then the exposure was correct again.