Autofocus issue

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HantsPete

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Pedro
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My Tamron 18-200mm VC lens doesn't compare well in terms of autofocus with another lens I've got.
I wanted to see how sharp the lens is at 200mm, so I did some tests. With autofocus (single point) on a small target, about 8 out of 10 shots are reasonably sharp. The other 2 are slightly off ie comparably softer. When I try the same test with my Tamron 70-300mm VC lens, 200mm with the same settings, the results are sharper, with no shots looking soft.

This is the second Tamron 18-200mm VC lens I have tried, both of which have this approx 80% hit rate in auto focus. So is this just down to the design of the lens, could both have the same 'fault' or am I expecting too much from a cheap lens? I would appreciate any comments or advice. Thanks.







T
 
the 70-300 lens at 200mm is closer to the difference (centre) between 70-300 than the 18-200 at 200mm which is at the extreme range of that lens. So less chance of focus issue

If your mainly using close to the 200mm with the 18-200mm lens I would try doing a fine tune in the camera menu for 200mm and see if that helps
 
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Thanks. I understand what you are saying about 200mm being the extreme limit of the 18-200 lens.
Is it fair to say that when shooting at 200mm with this lens, AF may be 'challenged' somewhat? As I mentioned, about 80% of the time the AF hits the target with sharp shots.
 
you don't say if your testing with the camera on a tripod or not when VC should be off. Not knowing the camera make/model I don't know if you have a fine tune in the menu which would be what I would adjust for 200mm. Always helpful if asking this type of question to say the camera type and model number and how your doing such testing.
Also what distance the target is from the camera
just one other thing worth a mention what is 200mm on one lens may be not exactly the same on another. A "target" may appear closer or further away in a photo when checked side by side from each lens



are you usng anything like this for testing

FoCal Pro Focus Calibration Software with Target or a SpyderlensCal target
 
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The camera is an EOS 4000D so nothing fancy. Also the 'test' I'm doing is very basic - a car number plate at 30m. VC on, aperture f8 shutter 1/200 and view finder. Handheld so I know there's a risk of shake - but I'm doing this on purpose just to see how well the lens performs in terms of vc and af. With the 18-200 lens there are times when I can see in the viewfinder that the af is very slightly off, even allowing for some camera shake. But as I said, about 8 out of 10 times it's OK. The other lens (tamron 70-300 vc) does not exhibit this af variation.
 
to test properly a lens you need what I said before . Human error has to be a built in factor otherwise
 
realspeed said:
to test properly a lens you need what I said before . Human error has to be a built in factor otherwise
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This.
HantsPete said:
The camera is an EOS 4000D so nothing fancy. Also the 'test' I'm doing is very basic - a car number plate at 30m. VC on, aperture f8 shutter 1/200 and view finder. Handheld so I know there's a risk of shake - but I'm doing this on purpose just to see how well the lens performs in terms of vc and af. With the 18-200 lens there are times when I can see in the viewfinder that the af is very slightly off, even allowing for some camera shake. But as I said, about 8 out of 10 times it's OK. The other lens (tamron 70-300 vc) does not exhibit this af variation.
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I appreciate why you’re testing like this; it’s ‘real world’, but it’s also including a lot of variables that aren’t the fault of the camera or lens.
Your test is just showing that there’s a failure, not that the lens is struggling.
 
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