What lens are you using with your camera? There are potentially three scenarios that will lead to the camera & lens not being able to acquire focus (this would also happen if using the viewfinder):
- You are too close to your subject. Each lens has a minimum focusing distance. So if you are closer than that to your subject, it won't be able to acquire focus. Note that the distance isn't measured from the front of the lens. The distance starts at your camera's sensor. There is typically a small symbol on the camera somewhere (usually next to the viewfinder) which is a circle with a line through it. That's where your sensor is at.
- Building upon 1 above, your lens has a focus limiter switch that is in the incorrect position. e.g. on my EF 135 mm lens, I can select one of two options. Either 0.9 meters to infinity or 1.6 meters to infinity. If I have the switch in the 1.6 meters to infinity setting, and I'm trying to focus on something at around 1.0 meters say, it won't work. I'd have to first switch to 0.9 meters to infinty.
- What you're attempting to focus upon has not enough contrast. Especially if the area you're focusing upon is all or mostly the same brightness. In this case, focus on an area that has better contrast (higher difference between lightest and darkest points). You can always re-compose the image before taking the shot as needed.
There are potentiall more scenarios, but those are the main ones that come to mind.
--
Ricky
Camera: EOS 5D IV, EF 50mm f/1.2L, EF 135mm f/2L
Lighting: Profoto Lights & Modifiers
