"Manual focus question : What do focus lights mean?"
I picked up a Nikon 50 f/1.4D recently, and am trying to learn how to use it. And frankly, I'm trying to learn if what I think are focus problems/lack of sharpness are hardware related or if I'm just not shooting it correctly.
Anyway, my specific question is this: When focusing in manual mode, the D7000 has the three indicators (left arrow, center dot, right arrow) that supposedly tell you when you have "hit" your focus point.
How do those work? What is the camera looking at to decide if you are in focus or not? Is the circuit that drives those lights related to the regular autofocus system?
#1. "RE: Manual focus question : What do focus lights mean?" In response to Reply # 0
Yes, that is a visual indication of what the autofocus system detects. It is evaluating the focus at the selected focus-point in the frame, so if you have objects in the frame at different distances, which focus point you have selected will determine which object's focus is being evaluated.
Because this uses the same circuitry as the AF system, it suffers from the same limitations. In particular, if the subject is one the AF system can't reliably focus on, the focus indicator will be unreliable as well.
If I were evaluating a lens for sharpness, I would use a tripod for the camera, a fixed, stable object as the target, and Live View as my manual focusing indicator.
#2. "RE: Manual focus question : What do focus lights mean?" In response to Reply # 1
Los Angeles, US
Here is another take. The > and < arrows indicate focus has not been achieved. If you were to manually turn the focus ring, the arrows show the way the top of the focus ring should be rotated.
> means, you rotate the ring clockwise, viewed from the shooters position. < means focus will be achieve if you rotate the ring counterclockwise.
The instant focus is achieved, the green light comes on. The arrows disappear simultaneously.
When using autofocus, the green light means that focus was achieved.
There are two mechanism controlling this, one when you are looking through the viewfinder. The other, when you have Live View turned on. One senses light phase, and one detects contrast. Whichever method, you have a fast lens and so the additional light coming through the lens means AF will be very fast. Dim light makes focus more difficult.