What are the settings and posture I should use when using the D7100 & 18-140mm for action sport? Action sport for me means my dog running towards me or away from me or running and stopping at intervals on a foot ball field.
This is about as broad as it gets.
Variables: Weather conditions, snow, clear, rain (mist)
Lighting conditions - time of day and location of Sun or cloudy day
Filters in use - will reduce exposure. You want to shoot wide open but it is too sunny and you need to stop down. You want the dog and clouds to be well defined with a blue sky etc.
Short version with any camera.
Single shot autofocus to lock onto the subject, stop the lens down as much as possible to increase the chances of a sharp result, use the rapid fire motor drive so when you press the shutter it rattles off shots. At least one should be in focus.
Use of a mono-pod is helpful as well.
Composition as close to eye level with the dog or any subject matter is always a good idea.
Metering mode could be matrix or center weight depending on the lighting.
Their is also a difference if you are stationary shooting or having to move fast, stop, compose and shoot. In this case using Release priority if the camera has it is an option.
*Look up how to shoot football or soccer, the dog could be a player running the field you need to shoot so the same idea applies with the dog.