Inconsistant focus and exposure

[Chilly]

I am using a 10D and am having trouble getting a consistant focus and exposure. I am rather new to the 10D so I feel I am missing something. I am currently taking pictures of kids with a lamb sitting on hay bales. 70% of the time all is ok but the 30% get rather frustrating and is usually the best expression etc. I can fix exposure in photoshop but that is time consuming. I use a 550 ex flash (raised to bounce off the white ceiling), tripod, I use a modeling light set close to the floor to help with shadows.

Using the "portrait" mode seems to get the best color but it concerns me that each time I depress the shutter button 1/2 way different focus points light up even though nothing has changed.

Also because there is usually more than one child if I just focus on the center of the picture it is actually in between the two kids which causes the camera to focus/expose on the hay behind the kids.

I've tried focusing then turning off the AF but how do you keep the exposure constant. Things have to move rather quickly and I am always changing the focal length from one customer to the next so I would like to stick with an automatic mode.

Any ideas on how to make focus and exposure more consistant?

[tim]

Most people use only the single centre focus point: you focus on the eyes of the person. If there's more than one person you'll have to use an aperture that's narrow to get everyone in focus, F8 or more probably. There is the a-dep more which automatically sets the depth of field for you, but i've never tried it myself. AI servo focus is another idea for things that keep moving.

Hope that helps.

[KennyG]

Firstly, get out of the auto modes, you have no control, use Av. Next learn how to compose your subjects. Then, read the manual on how to use the focus points correctly. If you are doing this seriously, then a couple of flash guns just isn't up to the job.

I am trying not to appear rude, but it looks like you really need to learn a lot more about the basics. Jumping in to studio work without understanding what you are doing isn't fair on clients and is obviously giving you problems. There are lots of books and courses to help you and then you should practice on friends and family before accepting paying clients.

[Hellashot]

I agree with KennyG. Most of the auto-modes should be removed from the dSLRs. I only started to get good images, on tougher conditions, when I went into the "creative modes". Full automode was often using autofocus points no one in their right mind would use.

Come to think of it, if you're using an external flash, at least with my Drebel, Av mode will not take into account your external flash and it will give you a shutter speed as if you had no flash. When using my external flash I now use manual mode and I disregard my exposure meter. I use either f6 and 1/60th or f8 and 1/80 and possibly a FEC of up to 1 1/3rd. I've only started using this method and have gotten decent results.

See what happens when your external flash is attached and you switch between P, Av, Portrait, and full auto.