Canon 5d mk1 won’t take an image if it thinks it’s not in focus

[DmelloMarfi]

My canon 5d mk1 and yongnuo 50mm f1.8 mk1 won’t allow me take a photo if it thinks the image isn’t in focus. This is particularly annoying as the autofocus on that lens isn’t very accurate and sometimes it thinks it’s not in focus when it actually is. Is this normal and is there something I can do to change this behaviour?

[wq9nsc]

You can switch that lens to manual focus and focus using the focus ring. 

What lens are you using?  You may need to select a single focus point to get the focus accuracy you desire by putting it on the critical area that has to be in sharpest focus.

Rodger

[ebiggs1]

A real Canon 50mm lens is around $100 bucks, brand new, and it is many times better than what you have. Plus it will work!

[MikeSowsun]

In One Shot AF mode, it is normal for the camera not to shoot if the subject is not in focus.

Try shooting with the Autofocus mode in AI Servo instead of One Shot. AI Servo is meant for shooting moving subjects and it will allow the camera to shoot even if the subject is not in focus. 

[Waddizzle]

What are you trying to photograph?  Make sure that you do not exceed the MFD, Minimum Focus Distance, for the lens, whih 45cm, or about a 1.48 feet.  Also, make sure that you have sufficient light for the camera to focus.  

If the Yongnuo lens is the only lens giving you trouble, then you have a lens problem, not a camera problem.