AF falls off at longer focal lengths?

[stevet1]

I'm using a Canon 55-250mm STM lens. I notived that the autofocus seems to fall off at the highest focal length (250).

I had to manually adjust the focus to fine tune it. The lens seemed to work just fine at around the 135mm length.

Is this normal in any lens?

Steve Thomas

[stevet1]

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Hi Steve.

To clarify - are you saying that focus is harder to achieve or are you finding that focus is not sharp when the camera states focus is achieved (green dot )?

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John

I'd say focus is harfer to achieve. It gets about 95% there. I've been shooting in AI Servo mode, so I don't get the little green dot. (I've got the beeping turned off also, so I don't have that auditory clue either),

I wasn't using a tripod, so when I tired using Live View and magnifying the screen, my hands were wobbling all over the place, so I gave up on that..

I really need to start using the tripod more.

I did take the color polarizer off, and I think that improved things. I need to run some more tests.

PS: I'm starting to like Auto ISO with a negative 1/3 exposure compensation.

Steve Thomas

[jrhoffman75]

Thanks for the clarification Steve. Understand about AI Servo.