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07-12-2013, 11:33 PM   #1
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FA* 28-70mm problems.

Just having a few issues with my FA8 28-70mm. I have tried it on three cameras so ruled out the camera as an issue.

I started to notice when I change a lens and put the 28-70 on I can hardly see through the view finder and looks very grainy. If I move the aperture ring around a few times it comes clean and looks fine.

The other issue is that there is no through the lens metering and to get a correct exposure I have to manually set the shutter / ISO / F stop myself.
I used the lens for eight weeks while we were in the USA and got used to manual exposure.

Even in all the camera modes it was the same so Manual mode was used.

I have tried cleaning the connections on the lens and camera but no change. I suppose its time to send it off to Pentax for repairs.

I have used it on my K10D,K5 and K5iis and no difference on each camera.

Any suggestions other than send it off.

John

07-13-2013, 12:42 AM   #2
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QuoteOriginally posted by campdog Quote
Just having a few issues with my FA8 28-70mm. I have tried it on three cameras so ruled out the camera as an issue.

I started to notice when I change a lens and put the 28-70 on I can hardly see through the view finder and looks very grainy. If I move the aperture ring around a few times it comes clean and looks fine.

The other issue is that there is no through the lens metering and to get a correct exposure I have to manually set the shutter / ISO / F stop myself.
I used the lens for eight weeks while we were in the USA and got used to manual exposure.

Even in all the camera modes it was the same so Manual mode was used.

I have tried cleaning the connections on the lens and camera but no change. I suppose its time to send it off to Pentax for repairs.

I have used it on my K10D,K5 and K5iis and no difference on each camera.

Any suggestions other than send it off.

John
Hey there,

I can answer your first one. Because of the aperture ring that is on all FA series lenses, at a higher # aperture which also means less light is coming to the sensor; naturally it will be harder to see and therefore also grainy. Doesn't the lens have the "A" setting? This means that you can control the aperture via your dial on your camera and it remains wide-open (to prevent the lack of light and grainy-ness). It will change to your desired aperture after you press the shutter button.

-Steve
07-13-2013, 12:48 AM   #3
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Original Poster
QuoteOriginally posted by thedollarbill Quote
Hey there,

I can answer your first one. Because of the aperture ring that is on all FA series lenses, at a higher # aperture which also means less light is coming to the sensor; naturally it will be harder to see and therefore also grainy. Doesn't the lens have the "A" setting? This means that you can control the aperture via your dial on your camera and it remains wide-open (to prevent the lack of light and grainy-ness). It will change to your desired aperture after you press the shutter button.

-Steve
Thanks Steve. The problem is that the lens is left in the A setting. When I put the lens on it is in A setting but I need to move the focus ring around a few times to get it to work. It does change on the camera with the dial but still issues with exposure. Maybe aperture blades are sticking.
Thanks
John
07-13-2013, 06:52 AM   #4
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It does sound as if you have a problem with the aperture blades sticking.

You'll note that when you look through the lens, when not mounted to the camera and the aperture control ring is set to the "A" position, the blades are closed. When you mount the lens, the camera moves the aperture lever on the rear of the lens to open the blades. In your case, the blades are sticking and not opening fully, until you move the aperture ring around a few times, which loosens the blades. Unless you're willing to take the lens apart, you'll need to have it fixed by a repairer.

I'm not sure what the problem might be in regards to your issue with metering, but if you've already tried cleaning the contacts, then the problem will be internal. Perhaps the leaky oil that's causing the aperture blades to stick is also getting into the electrical contacts, causing problems.

07-13-2013, 10:24 PM   #5
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QuoteOriginally posted by tom1803 Quote
It does sound as if you have a problem with the aperture blades sticking.

You'll note that when you look through the lens, when not mounted to the camera and the aperture control ring is set to the "A" position, the blades are closed. When you mount the lens, the camera moves the aperture lever on the rear of the lens to open the blades. In your case, the blades are sticking and not opening fully, until you move the aperture ring around a few times, which loosens the blades. Unless you're willing to take the lens apart, you'll need to have it fixed by a repairer.

I'm not sure what the problem might be in regards to your issue with metering, but if you've already tried cleaning the contacts, then the problem will be internal. Perhaps the leaky oil that's causing the aperture blades to stick is also getting into the electrical contacts, causing problems.
Problem Solved. About to pack the lens off for servicing and one more look at the aperture blads and connections. It felt a little stiff where the camera operates the aperture. The arm was a little bent and up against the lens body. That would have been causing the aperture blades to stick and also throw out the metering as the rest of the esttings were changing but the apeture staying the same.
tried in all settings now and working fine.
I must have bumped it at one stage but cannot remeber where as I am vet careful with my gear.
John
09-08-2014, 05:56 AM   #6
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Hello Everyone, Ive found my Fa*28-70 is very soft at 70mm wide open, almost unusable, some one can tell me if I can fine tune the autofocus without damage the other focal length.? I have a K20D
09-08-2014, 07:57 AM   #7
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QuoteOriginally posted by dinamojuan Quote
Hello Everyone, Ive found my Fa*28-70 is very soft at 70mm wide open, almost unusable, some one can tell me if I can fine tune the autofocus without damage the other focal length.? I have a K20D
that is probably going to depend specifically on your copy of the lens, whether focus adjustments at one end of the zoom range will improve or worsen focusing at the other end.

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