Slight problems focusing with EOS 3 and 100-300mm 5.6 lens combo

[robert_freiberger]

Hi,

 

Last Friday I got the first chance to test the EOS 3 in a action

setting. While photographing the motorcycle racers at Laguna Seca I

noticed that the 100-300mm lens was having a slight problem with I

focused on AI servo. What would happen is the lens lock on the

motorcyclist approaching, then the camera would back focus, then

after a second focus on the motorcyclist.

 

After a few times of this I just switched to single focusing, and

locked the focus to a point where I knew the motorcycle would pass.

This proved to be more successful.

 

My question is the lens causing this problem? I haven't noticed any

focusing problems with my 50mm 1.4 or 28-105mm lens. Would a higher

performance lens such as the 70-200mm 2.8 lens offer better focusing

with high speed action?

 

Thanks,

Rob

[jean_berthe]

Hello Robert

 

I remember having problems with "slow" lenses when I upgraded to a EOS3. If there are not enough horizontal contrast on your subject, the "vertical AF sensor" has nothing to lock on. If you were using another body (ElanII, Elan7, A2, etc) you would get a center cross AF sensor, which would lock with vertical OR horizontal contrast subject.

 

A faster lens (f4 or better) should provide better AF lock/tracking. It took me a few years to upgrade most of the lenses I use to mostly f2.8.

 

Good luck

 

JB

[oofoto]

I also have this combo - the lens is too slow and this causes the auto focus mechanism and motor to hunt. Absolutley the lens. I don't shoot sports so it's not a problem for me.

Regards

[PuppyDigs]

The EOS 3, 1V, 1D, 1Ds, 1D MKII all need F4 to fully enable the center cross sensor. Otherwise it degrades to single axis sensitivity only and has difficulty getting an AF lock. To fully activate the center cluster of 7 cross sensors you need F2.8 or faster. With an F2.8 the AF system really shows its stuff. A slow zoom is an exercise in frustration...

 

You may improve AF with slow lenses by setting CF 17-1 (cluster AF).

[robert_freiberger]

Thanks for the replies,

 

I figured it was the lens. Since the majority of my photography is landscape and still life I can make do with the slower focusing but this is on my upgrade list for later this year.

 

Rob