Question on focal point & DOF

[Mr-Beama]

hello :)

i am shooting a friend of mine with his 3 greyhounds. the greygounds will be in the front of the shot and then my friend with be hold their leads at the back. (like a horse and chariot kind of thing) i have to be quick as the dogs are moving.

the problem is where to focus. the shot is outside in woodland area.
i wanted to use 200 iso (i found iso 400 a bit noisey on my 10D) but this gives me about 1/90 @ f5.6 this either made the dogs (in front) or my friend (in back) out of the depth of field.

so my question is do i focus somwehere in the middle to get all subjects in focus? and how can i work out the distance from my focal point what else will be in focus?

many thanks :)

[akhater]

try adep mode to find the correct f stop then boost iso to meet it with the correct speed

[StewartR]

I think you've run into one of the fundamental problems of photography. You have three basic requirements:
shutter speed: fast enough to avoid the dogs being blurred;
ISO setting: low enough to avoid noise;
aperture: small enough aperture to give you depth of field to encompass your friend and the dogs.
To do all that, you need a lot of light. So woodlands are not the ideal venue. Why not take the shot outdoors in the sun? You should be able to manage say 1/250th at f/11. Or you could try stopping down the lens (to get a bit more depth of field) and using some fill-in flash...

If you want to calculate exactly the depth of field you would have in a given situation, DOFMaster (http://www.dofmaster.com/dofjs.html) has an on-line calculator.