2. Focus Recompose, The Enemy Of Shallow Depth OF Field
When working with a shallow depth of field, you may have a very small amount actually in focus. Depending on the focal length of your lens, distance to your subject, and the aperture you have chosen, you may have anything from a few inches to a couple of millimeters in focus.
Focus recompose is a technique made popular by cameras that possess some focus points that, putting it kindly, are best avoided (think Canon 5D Mark II). When using cameras like that, photographers often stick to using the center focus point (normally the best) and then recomposing the frame once they have gained focus. The key point here is that by doing so, they have to move the camera. If your depth of field is only as wide as an eyelash, then you could very easily shift that focus with your movement.
Instead, try to select the focus point as near as possible to the point in your scene that you are focusing on, thereby reducing or removing altogether the possibility of losing your focus as you recompose your shot.
This method would be ideal, but as I have already mentioned, on some cameras only the center focus point is worthwhile using. In those cases, your only option is to use the focus-recompose technique. It then becomes critical that you are acutely aware of your movement and that you regularly check the focus on important shots.
3. Movement Of Any Kind, Yet Another Enemy Of Shallow Depth OF Field
It seems that shallow depth of field has a lot of enemies! That’s no surprise when you’re working with what could potentially be as little as millimeters in focus. Following on from the last tip (focus recompose), we have to think about all movement. If the camera moves a millimeter or two, we’re off. If our subject sways back and forth by a millimeter or two, we’re off. You must contemplate the movement of everything in your scene and use that knowledge to make better decisions.