Auto Focusing Issues - Please help

[chilli_vision]

Hey Guys,

What can affect my lenses auto focus from connecting with the subject?

I have been playing with my 55-200mm lens on a x1.5 crop camera and I have noticed that sometimes it doesn't want to auto focus an beep. I don't think there is an issue with the lenes, i.e. not fucntioning corrently, I believe this is more down to user error.

So, what I have been doing is playing around with focal lengths to subject distance and different subject textures, i.e. detail-less and glossy to lots of detail etc, to see what my camera/lens combo likes to focus from, but I've not quite yet caught onto what it likes to do best.

Is there anything I else need to consider (other than being too close or not having enough detail to focus from) that will be a major thing that will cause the camera/lens to get confused and not auto focus.

Matt

 

[Donki]

The amount of ambient light can affect focusing, dimmer conditions can cause lens so "seek" which basically means struggle to focus. The size of aperture used also affects focusing (as it determines the amount of light that enters a lens). Of course the speed and ability to focus will also differ from lens to lens. The subject also effects focusing as you say i.e. contrast in light, texture even colour of the subject.

 

[TCR4x4]

The focus system usually uses contrast, so if you are trying to focus on something that is all one colour, you will struggle to get a lock.

If you focus on a point where there is a tonal or colour change in the subject, providing there is enough light, you should get a good lock on.