Minolta grinding lens

[clueless1951]

I recentely bought a used 5D. I have a QTsi 35mm camera and wanted to interchange the lenses. I recieved a AF DT 18-70 lense with the camer everything worked fine. I have a Sigma 28-200 lense that I had on my QTsi it worked fine on the 5D for over 20 days. Then it started to grind when I turned it on or off. I put the 18-70 back on and that worked fine. So I thought it was my Sigma that broke. My grandson wanted to take it out west so I gave it to him. He had a Tamron 300 mm lens from his QTsi he put it on my 5D and it starting to grind just like my Sigma. When we put the Minolta 18-70 back on it works. I tried the Sigma back on my Qtsi and it is still grinding so I must have ruined it. When it grinds it is the auto focus trying to focus .......I have tried to move it slightly by hand to get it to stop grinding. Any help out there???????????????

[DonSchap]

I believe the problem you are encountering is with the screw head interface between the lens and the camera body. They just are not locking together properly. I have precisely the same problem with one of my older Ozunon lenses. I put it on my Maxxum cameras ... works just like downtown ... on the SONY a100 or a700 ... it cannot interface tightly the screwdrive. You might contact SIGMA to see if there is some level of repair you could perhaps do on your own, but I do not have much hope in a good result from that.

There just the slightest over-size of the Minolta digital camera body screw head (it carried over to the SONY, too) ... and wham, you are out of business. The screwdrive blade is only lightly spring-loaded to press into the lens reciever slot. The newer lenses have been "adjusted" or modified to cope with this digital screw head size. I have yet to see it reoccur with them, which explains why your DT 18-70 works properly.

I'll add photographs to point out the location of the issue, later

[clueless1951]

Thank You very much for your feedback. I live in a rural area so I am going to try and get to a repair center. I just don't understand why it worked for over 20 days them WHAM. It must have done something to the lense because it now does the same thing on my QTsi.. Just got a call from my grandson and he said he took over 600 pictures with the 18-70 that came with the camera so all is not lost. Thanks Again

[DonSchap]

Oh, it is definitely the lens' response to the drive. It has to be, because the camera works with everything else. These older lenses worked with a much slower focus speed on the film cameras. The torque involved in engaging them, now ... it much higher and several SIGMA/Quantaray lenses (70-300mm) focus gears have been literally stripped and shredded inside by these "improved" focus systems.

Here are some sample images of the damage you appear to be describing from a SIGMA lens.

37183

37184

Your best solution, if the lens is not that expensive, it to buy a new digital-rated lens. Do not get me wrong, I am not a "buy new gear advocate", but new lenses are designed for these newer high-end focus drives and will more than likely be error-free. Using old lenses does have a couple issues, some with accurate and sharp focus and others with issues like this. It really is toss-up when you use them.

Good luck ... with your NEW lens.

[clueless1951]

Thanks for the pics it looks like what I am hearing grinding metal. Will have to get a new lense I already bought a used on for the Qtsi on Ebay and it works fine put the Sigma back on and it is grinding away. Thanks for all your help.

[DonSchap]

Well ... it is becoming a known issue. I am glad to have shared some insight on it.

Good luck with your replacement lens.