When I use the manual focus mode, I usually adjust it until the object I care about comes into focus. But sometimes the object is not there yet, so I'd like to know if there is a way for me to tell the camera to focus X meters away. This is with the Sony NEX-5R.
An example of when this is needed is when I'm setting up my camera to shoot a train that will appear at a specific point ten meters away from me. I can't focus on the train since it's not there yet, but I need to set the focus ahead of time to have a good chance of taking a shot. (This is a long exposure, low-light shot.)
Autofocus does not work reliably for this lens under low-light, and if I wait till the train comes by before I focus, I might miss the shot, and in any case, it's hard to manually focus on a quickly moving train.
Is there a way for me to tell the camera to focus X meters away, other than finding some other object X meters away, moving the camera if necessary to find such an object, focusing on it, and then moving the camera back to the desired position?
Or is there some other solution to this problem that I'm overlooking?
A special case of this problem is needing to focus on infinity. As I adjust the focus, I don't know which point corresponds to a focus at infinity.