What is the best way to get two subjects in focus in a portrait (sometimes not at the same distance from the lens)? Obviously, this is a question of depth of field, but I am curious what some of the best tips are to get a sharp image with multiple subjects at different distances.
In case it helps, I'm using a D800 with a 50mm lens, typically at f/1.8 (aperture priority mode).
Best bet is to carefully understand the Depth of Field that your chosen settings will provide, and position your subjects accordingly, or change your settings.
With the setup you provided, if your subjects are 5 feet away, you have a total of .32 feet or about 4 inches of depth that will be in focus. Therefore, your subjects need to be equal distance from the lens, to be in focus. This will require measurements to be sure of focus most likely, therefore, you may want to consider changing your set up to be more favorable to ensuring sharpness of focus:
If you stand 10 feet away, you have 1.3 feet of area in focus.
Better yet, if you change your aperture to f/8, you have about 1.5 feet of focal depth, so any offset distance between two side-by-side subjects will be minor, and both will likely be in focus.
To calculate these distances, refer to the excellent, and always helpful DOF Master
Another option would be to use a tilt-shift lens to allow you to keep 2 subjects in sharp focus at different distances whilst maintaining a wide aperture
Another option that might be viable is focus stacking... used mostly in macro, but might work in this instance.
– Digital Lightcraft Sep 25 '13 at 09:57Learn to use the depth of field preview button on your camera.
Looking at the camera, DOF-preview is the upper button next to the lens, falling under your middle right finger as you hold the camera. Pressing it stops down the lens to your chosen aperture, so that you can see what is and isn't in focus at that aperture. If they're not, choose a smaller aperture until they are.
Also, remember that depth of field depends in part on the distance to the subject(s): you get greater depth of field as the distance to the subject increases. Taking a few steps backward may help bring both subjects into focus.
Adjust your shooting so that you have a wider depth of field. That's the only option. The easiest way is to use a slower aperture, but that means you need a) more light and b) may run in to reduction of sharpness from diffraction. Beyond that, you can also adjust your distance from the subject and your focal length, but those two fight each other, so it can have a limited impact on your ability to get a wider field of view.
Alternately, you can also shoot with a smaller sensor. The smaller the sensor, the more effective magnification you get for a given focal length and the smaller the amount of blur you will get, so you'll have more tolerance on the depth of field with a smaller sensor as well.
