Madison,





All you need is this...


DOF Calculator


DOF has to do with a lot of things. Distance to the subject, focal length,apperature, and even if your using a FF or crop sensor. The calculator will help u with deciding what you'll be able to get in focus. Don't forget after a certain point defraction will be a concern if you use too high of a f-stop. Usually it's said you want the eyes in focus but if the teeth are your main subject you may have to live with the eyes being a little out of focus if you can't use a smaller apperature. I believe all Canon cameras have a DOF preview button next to where the lens is mounted that if you press down the image will get darker inyour viewfinder but it will allow you to see what will be in and out of focus. You might choose to focus on a point between the teeth and eyes since when the lens is stopped down there will be a point in front and behind your focus point that is still in focus (see "in front of subject" & "behind subject" in the online DOF Calculator) Hope this was somewhat helpful.





Fred~