Determining DOF

Glenn NK wrote in post #5844038
From what I've read, this relationship is good until you get to macro distances, then it falls apart (where it's more 50/50).

Yeah, I believe so. However DoF is so shallow with macro anyway that you need to focus exactly on the point you need sharp anyway. I shoot a lot of preying mantids and have to focus on the eye and just let Dof fall where it may. Focusing even slightly behind the eyes, to put more of the DoF over the body, makes the shot look soft as the eyes aren't pin sharp. In fact it's not always possible to get both eyes sharp, even though they are only 2-3 mm apart.

With macro work, the only way I attempt to judge DoF is with the DoF preview button, which actually seems more effective in macro situations than normal shooting. I will sometimes focus slightly away from the critical focus point, if the DoF preview shows it will be OK, but I would never attempt to use any 33/67 or 50/50 ratio to guesstimate the best point to focus at with macro.

As the OP was asking about controlling DoF in shots of a model sitting on a car, I figure the difference for macro isn't important to them. You raise a good point though.

sandpiper wrote in post #5844147
Yeah, I believe so. However DoF is so shallow with macro anyway that you need to focus exactly on the point you need sharp anyway. I shoot a lot of preying mantids and have to focus on the eye and just let Dof fall where it may. Focusing even slightly behind the eyes, to put more of the DoF over the body, makes the shot look soft as the eyes aren't pin sharp. In fact it's not always possible to get both eyes sharp, even though they are only 2-3 mm apart.

With macro work, the only way I attempt to judge DoF is with the DoF preview button, which actually seems more effective in macro situations than normal shooting. I will sometimes focus slightly away from the critical focus point, if the DoF preview shows it will be OK, but I would never attempt to use any 33/67 or 50/50 ratio to guesstimate the best point to focus at with macro.

As the OP was asking about controlling DoF in shots of a model sitting on a car, I figure the difference for macro isn't important to them. You raise a good point though.

I have given up on small apertures for closeup/macro work, and now resort to focus stacking. Typically I shoot at f/4 to f/5.6 (which eliminates any crappy backgrounds) and take anywhere from four to twelve shots.

Of course, this can be used for landscapes as well provided that wind doesn't move things around between shots. I wouldn't try stacking with live people though.