Focus Problems horse jumping - Nikon D5100

[astroNikon]

Derrel
That's interesting
Is it lens quality or he amount of light it lets through
Is this inherent in none fixed aperture lens or just this lens in general?

 

[gsgary]

A have shot horses for years and hardly ever use auto focus when shooting jumps

 

[cwindle1]

I all sorry I haven't been able to communicate as laptop messed up.

I tried all sorts on the day, 3D tracking mode, dynamic mode (with panning with the horse!), AF-S ect. Do you think my lens has a problem? or my camera? It's just confusing that it's always down to the jumping. Flatwork images turn out fine...

 

[Derrel]

I got a PM about the 70-300 VR lens and my comments on its AF reliability. Here's what I wrote back:

It's a design issue the lens has. Ken Rockwell mentioned it in his review. sm4him has experienced the issue. I have the problem with it periodically. It's NOT all that rare in the slower, long-ranging zooms. WHat the issue is is if you pick up a target that is CLOSE, the focus racks wayyyy in; then if there's a target that's far away, the lens may refuse to initiate AF. Or reversed, far target, then a closer subject. As Ken mentions, the AF is fast as long as you are relatively close to the proper focus distance.

I'm not sure why, but mine does this all the freaking time, even at the beach, where there's a lot of light. Here's what Ken mentions, "If you start off completely out of focus (subject at 6 feet and lens at infinity for instance) you may need to move it manually to get it started, and if it's way out of focus it may first focus in the wrong direction, bounce off the stop and head back the other way to acquire your target. So long as you're in the right zone, focus is fast!"

I had nightmares with it on age 10-11 soccer, focusing on close players, then having the lens need to manually be directed back toward action on the other side of the field after a pass. It will FOLLOW focus pretty well, but does not have the INSTANT ability to go from say 10 feet to 60 yards every, single time, reliably.

I blame the slow f/4.5~5.6 max aperture for this, which is only marginal f-stop wise for the best AF. There's less IN, less OUT of focus for the phase detection with a slowish lens, so the actual focus data the AF system has is weakish.

Compared to like the 70-200 VR or a couple other primes (200,300,105), the 70-300 VR is not in that 99.5% reliability for ALWAYS autofocusing on a newly-acquired target. THAT is really the issue: it's reliable,consistent initial acquisition of targets at any distance...it just cannot be relied upon to acquire a sudden, new target if the focused distance initially is significantly greater than "normal", without needing some manual override of the focus ring. It's not horrible, but compared against the 70-200 VR or 80-200 AF-S or 300/2.9 or 200/2, the lens is decidely lower than what I call 99.5% reliable. As long as the targets are all at XX yards, it does pretty well though.

 

[astroNikon]

Basically it's not a pro lens And really I have to use the 70-300vrii just like my 80-200/2.8 AF-D lens. That's not problem as I got used to it. So single focus point is it.

 

[Braineack]

I've had that issue at times with the lens. But it's much better than the 55-200 VR and 55-300 VR ever were in that regard.

But I can get my 70-200 2.8 to do the same in tricky low-contrast low-light situations.