anyone experiencing this: AF-problems A99II SSM because of short screws

Started 2 months ago | Discussions thread
Michael Fritzen Veteran Member • Posts: 6,371
Re: anyone experiencing this: AF-problems A99II SSM because of short screws

gussman wrote:

...Just with this couple of shots (max 20) i found out that the 70400 was more reliable than the 28300PZD, both AF badly unless very well lit (which means outside, it is 13.00 hours over here) and AF is to unregular (with the advantage till now to the 70400)

Hi,

owning myself an A99II and the 70-400 (though Mk1) and doing along the last years pretty frequently action/sport with this combo (as well as with the 70-200, and the Sigma HSM 24-70 and 12-24) I've never felt very confident with the cam's tracking AF. For slower moves approaching the cam like runners, yes, it keeps track, best when shooting in short bursts, but for example upcoming bicycle, well, simply too many shots OOF. I got better rate in AF-C (only, w/o tracking) and moving the cam to have the subject where the AF area was set (zone or expanded flexible).

What I don't understand in your comments is how the lens would "flex" in the mount when one would hold the cam with the right hand and have the left holding beneath the lens (or have it for example monopod-supported). Holding/supporting this way there should be very low flex forces acting on the mount.  If you have the feel there's too much play in the mount then I'd check the screws whether one or more are not thoroughly tight.

Other than that no help here since I haven't experienced yet one of my lenses loosing contact.

Just another idea - however pretty unlikely to happen at more than one lens: did you check the AF/MF switch on the lens which might be in a middle position or having a bad contact. Some moves back and forth? Or the AF/MF switch on the body, do you touch it accidentally perhaps?

The shorter-or-longer-screws doesn't sound to me very likely. I don't see why a longer screw would fix the mount better than a shorter - as long as the shorter doesn't mean too short that it runs the risk to break out of the thread. A longer screw could only exit the opposite side of the thread - but this doesn't mean that it's "stronger" in any sense.

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Cheers,
Michael Fritzen

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