Can't get focus lock on

Hi there,was at the first race of Scottish Mx championship at Tain today ,came home downloaded the card ,hardly any of the shot were in focus ,not a happy bunny because we couldn't have had better weather .

This is my second outing with the K10D and sigma 17-70 f2.8-f4.5 shooting Mx ,getting a bit disillusioned now ,it's not as though i'm a new comer to shooting Mx .Here are a couple of examples.The exif information hopefully will help if it's me (i hope it is,but i'm not doing anything differently from when i had canon and pentax before )Thanks for looking and i eagerly await anyones advise and help .

Your's seriously frustrated Tog

1...

[IMG]http://i860.photobucket.com/albums/ab168/mxfun10/imgp7523.jpg[/IMG]

2...
[IMG]http://i860.photobucket.com/albums/ab168/mxfun10/imgp7494.jpg[/IMG]

3...
[IMG]http://i860.photobucket.com/albums/ab168/mxfun10/imgp7493.jpg[/IMG]

The EXIF says the camera was in manual, were you on manual focus?

it seems to me that a shutter speed of 1/320 is extremely optimistic given the subject matter, you need to up the ISO to around 400 and get the highest shutter speed you can. The pictures seem to have a fair amount of camera shake as well as being OOF.

It doesnt seem likely to be shutter speed. Not at that speed. Nothing seems in focus.

I had the same problem with my Sigma 17-70.

That's a real shame .. looks like they could have been a good set of pictures. I had the SIgma 17-70mm and it wasnt exactly the fastest of lenses but should have been fine with this.

in the first shot nothing seems to be in focus.did you have it on manual focus?
my sigma is fine

What Autofocus mode are you using on the camera? I noticed that in your first shot you have two subjects of interest, both of which are blurred and both of which are not in the centre of your shot. Perhaps on this occassion your camera focused on the hills in the back ground. Also, both the motorcylces are part of the mid and foreground of your shot which may have confused the camera on where it needed to focus. Also with your other two shots, the distant back ground appears to be more in focus than your subject. I had a similar problem myself but it was down to operator error and someone advised me to use use AF-C for continuous focusing on fast moving subjects. I usually tend to avoid the Manual setting for these types of shots and stick with Aperture or shutter priority just to let the camera do some of the work for me. I'm no expert by the way and I don't doubt your experience but it is something that has happened to me! Good luck in sorting the problem.

Thanks for all the replies. Focus setting was AF-Center spot fixed .I see where your coming from about the camera might have been confused in the first shot ,but the other two no,most of the other shots taken were filling the view finder ,been shooting Mx for a while now ,my guess is it's the lens or body . There's another meet soon so i'm going to try the 18-55 kit lens which i've used before when i had the K100D just to see .Would it be worth sending it to be checked out by sigma ?.

Shutter speed isn't an issue with these style of shots that's my norm ,maybe a wee bit higher but not much .

Thanks again for your feedback

Have you checked the K10d/sigma combination for front and back focus. It's a known problem, have search in the forum.

Trouble with that is that from the look of those pictures there is no focus point at all.

I see your point.

I did a practice session with my K10D in Spain a year or so ago using AF.C, centre focus and Sigma 70-200mm f2.8.

Yep used to have the sigg 70-200 when i had canon. The best combo i've used for mx to date was ,the K100D and siggy 24-70 f2.8 and the humble but very effective kit lens 18-55,was looking back at some last night cursing that i sold it .couple of examples .

1
http://picasaweb.google.co.uk/lh/photo/NWIMqNcpBKfd07lG0dUBLA?feat=directlink

2
http://picasaweb.google.co.uk/lh/photo/qIyC__zSsVeqihLU4ooqiQ?feat=directlink

3
http://picasaweb.google.co.uk/lh/photo/p22bYt_aju1Ag-oX7vOTiQ?feat=directlink

Maybe it's time to say farewell to the 17-70 you've now, it does not seem to be a good copy since your other shots are stunning!

Stefan, those were done with a K100D .. not the K10D used on the first shots so still dont know if its the camera or lens.