As ignite commented, if your "object" is relatively flat (like a coin, for example, or the face of a watch, you should take care to have the object oriented parallel to the sensor plane, so DOF is not an issue. The more obliquely you orient it, the more of an issue you have.
If your setup requires DOF, it's good to remember that DOF extends 1/3 in front and 2/3 behind the point of focus; if you have 3mm of usable DOF and you focus at a point 24mm from the camera, your DOF extends from 23mm to 26mm. This is why we almost always use manual focus for critical macro work; our focus point will not always be on what we consider to be the most important part of the object, but rather on an arbitrary point such that the "important point" falls within the range of the DOF while the actual field of focus is oriented as we visualize it. This is very difficult to do with autofocus.
I will frequently, when doing macros of a static setup, insert a "marker" into the image at the point where I wish to focus, do my focusing, and then remove the marker and shoot. I'll bracket my apertures (working in Av mode if not full manual) to find the one that works best for the shot. The differences can be extreme.
Robt. |
