Are you using AF-C ?_- -_- -_- -_- -_- -_- -_- -_-To shoot or not to shoot.......
I would do a focus test with that lens. I've heard of many people having focus issues with Sigma lenses. I would take several objects and line them up one behind another, but stagger them so you can see them all in the frame. Now, pick one, AF on it, and snap the picture. Is the one you AF'd on in focus in the picture, or the one in front or behind? If it's in front or behind, repeat the test with another lens to see if you have the same problem. If not, that rules out the camera and I would see about getting that lens replaced..
'I reject your reality and substitute my own' -Adam Savagehttp://www.flickr.com/photos/mrnoronha/sets/..
Have you tried spot mode focusing ? .
Pentax K100DFuji S5200Fuji E900PCLinuxOS..
When you say spot mode focusing are you compring that to "dynamic"?..
When you say spot mode focusing are you compring that to "dynamic"?.
That is not correct. Generally "spot" is used for metering (setting the exposure) while "dynamic" is used in terms of focusing..
There are generally two types of focusing, dynamic and single area, there is also auto but it just selects between the two. Choose either single or dynamic for you photos, my manual says dynamic which has you focus on an object and as it moves the camera will recognize this and re-focus on the object, this type of auto focus requires several AF points to properly track the object. You could try single and center your subject over the Af point selected as well but a fast moving object might make it hard to use. There may also be an option on how big the center focus region should be, look for it and select the largest size..
My best suggestion thou is to step down the lens (higher F number), this will increase the depth of field and give you a better shot and getting a lot more of the subject in focus and help negate a bad focus point. I bet thought that this will screw up your exposure but give it a try..