Depth of field is the region of sharp focus in a photograph. You can select an object to be in focus when depth of field is applied to the scene.
This page describes how to adjust depth of field in the Maya viewport. To adjust depth of field in your Arnold for Maya renders, consult the Arnold for Maya User Guide for information on the Arnold camera attributes. For information on depth of field in compositing, consult this tutorial: Z Depth AOV.
If you select multiple objects, Maya uses the center of their bounding box to calculate the distance from the camera.
In this example, the apple in the center of the bowl is selected to be in focus. The Heads Up Display indicates that its distance from the camera is 4.46. Depth of Field is then enabled, and this value entered as the Focus Distance.
Depending on the fStop and Focus Region Scale values, parts of the object may or may not be in focus. (Focus Region Scale adjusts the Focus Distance value to increase or decrease the distance at which objects appear in sharp focus. See Camera Attribute Editor for a description of these settings.)
Adjust the Depth of Field > F Stop value to increase or decrease the amount of depth of field. Use a higher fStop value (for example, f-16, f-22, f-32) for a deeper depth of the field where more of the foreground and background is in focus. Use a smaller fStop value (for example, f-2.8, f-4 or f-5.6) for a shallower depth of field, where more of the foreground and background is out of focus and blurred.