This is the first time I have had this issue. Why are the subjects faces out of focus? I am using a d300s with a sigma 70-200 f2.8. Images are straight out of the camera. Was using continuous focus and the focus point was the center of the frame. I noticed that for some reason the camera was having a hard time focusing all day, mainly on subjects that didnt have alot of detail at the focus point. I was shooting at f4 and iso400 in apt priority. I have never had this problem before but this is the first time I was able to be so close to the action for this type of event, I was right on the coarse.
My thinking is........ it was having a hard time focusing because of lack of detail at the focus point it couldnt find anything to focus on. Later in the day I switched the focus point to a higher section of the frame to focus on the faces but wasnt not able to see the images due to having to hand back the cards to the event photog company. And also being i was so close to the subject that maybe I should have been shooting at maybe a higher f stop like f8?
Any info would be helpful.

Notice how all the faces are blurry but the center mass of the subjects bodies are in focus.

Originally Posted by QuadRacer041 This is the first time I have had this issue. Why are the subjects faces out of focus? I am using a d300s with a sigma 70-200 f2.8. Images are straight out of the camera. Was using continuous focus and the focus point was the center of the frame. I noticed that for some reason the camera was having a hard time focusing all day, mainly on subjects that didnt have alot of detail at the focus point. I was shooting at f4 and iso400 in apt priority. I have never had this problem before but this is the first time I was able to be so close to the action for this type of event, I was right on the coarse. My thinking is........ it was having a hard time focusing because of lack of detail at the focus point it couldnt find anything to focus on. Later in the day I switched the focus point to a higher section of the frame to focus on the faces but wasnt not able to see the images due to having to hand back the cards to the event photog company. And also being i was so close to the subject that maybe I should have been shooting at maybe a higher f stop like f8? Any info would be helpful. Notice how all the faces are blurry but the center mass of the subjects bodies are in focus.

You answered your own question, being that close if you wanted there face in focus that's where your focus point should have been at 2.8 If you would have shot at f4 or f5 would have helped.

They were shot at f4 but I guess stopped down a little more would have helped.

Originally Posted by QuadRacer041 They were shot at f4 but I guess stopped down a little more would have helped.

I'm sorry I just woke up and the f4 @ iso 400 didn't sink in

If you take a look at an online DOF calculator, you'll see that at 20 feet, F4 and +/- 135 to 150mm you'll get a total DOF of about 4 to 8 inches. About half of that is behind the focal point and half in front. I don't know what distance you were, but DOF could indeed be the problem.
I used this calculator: http://www.dofmaster.com/dofjs.html

I bet your later in the day shots you didn't get to see were much better. What you want in focus should be what you point the single point selected at. Otherwise you are depending on DoF to fix it for you and as Vagebond stated, that ended up being 6 to 8 in inches. When composing shots like this I always have the single point on the face, not the center of the body. Also always check yourself with DoF preview as well as when chimping your shots, zoom in and look all over to see what you are really getting when the opportunity presents itself. Doing so early, for example just shooting at a bystander before the participants arrive, can really save you quite a bit of fumbling time both in exposure and focus. Doing so might have allowed you to rethink and maybe even to stand a bit further back to get some yummy bokeh, but still have your subject (the face) in focus to your expectations.

Oh... and maybe try to look for a cleaner background next time. The last one was almost perfect in that regard. ;)

Try single point focus on the face. So how did you like shooting Spartan?

Thanks for the info guys.
I really liked shooting at the Spartan, I have been to a few before and just shot on my own for personal shots. This was my first time working for Nuvision, I would do it again for sure. Other photog's I met were cool and I really enjoyed it. I wish I had a more interesting obstical to shoot but no big deal.

Its a great time isn't it? It doesnt even feel like work until day 2 at about 3pm. This will be our 3rd year working with NuVision and Spartan, both great organizations.