AF on the Da 55-300

Having recently purchased, smc pentax DA 55-300 f4-5.6, Generaly I am realy pleased with it but have found at the 300 range AF goes haywire in certain modes (bird pics against bright sky).
I have made sure (doubly) that object is in viewfinder,have even focused manualy but as soon as shutter is pressed af screws it up by going crazy, sending lens in and out and ending up out of focus on all(it cant find anything).
If anyone can help resolve this it would be aprieciated,
35mm I had no problem with at all but swapped to digital and a whole new learning curve starts.
Dont know if I should be using Av mode or manual thought it could be done in auto though, or, do I have a problem with the lens!! hope not!!.

There was a bit of a discussion about this the other day. Not sure if your problem is the same, but it might help.

https://www.pentaxuser.com/forum/topic/fs--new----pentax-da-55-300mm-f4-f5-8-ed-...

What camera are you using the 55-300 with? It used to do this on my K-x, but using it on the K-5 has transformed the focussing performance and I rarely have a problem now.

Regards
David

Pressing the shutter release half way will set off the AF system, so manually focusing first will only be any good if you switch the camera body to MF.

With a 300mm lens you have to be holding it very steady for it to focus. It's no good if the point you are focusing on keeps changing. I use MF most of the time, if your photographing birds, branches can effect the AF and only MF will catch the bird.

With AF focus on something further away manually or AF first then the AF just has to bring the focus in abit for the bird.

You need to set your focus to centre point only for
birds in trees or MF using the green indicator and beep.

I think that the AF can be de-coupled from the shutter button (though I've never done it). With this setup, you AF with another button and the shutter button only fires the shutter. This may help you as AF while tracking a fast-moving subject will be tough, especially with the 55-300, which has a very long way to turn from closest focus to infinity.

I personally find against high contrast skies AFS works better than AFC as it does tend to hunt back and forwards as described at 300mm. I use centre point AF for all long tele shots. I generally use TAV mode at 1/500th and F8 when enough light allowing the auto ISO to correct restricted to up to 1600. I also tend to set to just shy of 300mm on the zoom for better quality as others have suggested on here.

I find using the quick focus ring useful too for minor corrections and of course as its a DSLR, manual focus

Using the 55-300 on my K5,same body as previous, shooting against a very bright sky, with center focusing and switched to Mf, seems to have helped tremendously, especialy as the point of focus keeps changing, good ol mf.
as to using the green indicator and beep, I know where you are coming from Algi. butnhave to figure that one out in the menue first, will get there though.
I think by de coupling the shutter buton from AF and assigning it to another button may work, might try this just to see.
AFC and AFS at this moment I do not understand at all, !! may be simple but I have not encountered it but will try tav mode and see what happens.
I do try to keep camera on solid footing wherever poss..
Thanks everyone, all advise taken on board,will post some pics shortly with the 300mm.

Thanks all, having now tried various combinations whith the K5 and 55-300.
For me, the Tav setting whith MF I get on best with as still alows adjustment where needed (maybe residual 35mm tendancies, preferring manual).
the longer I have this K5 the more amazed I am with it`s functions!! (big learning curve).
took this today, quick shot during tea break app 1000 - 1500ft heigh hand held.
comments welcome.

Rob W.