Do I use the camera or lens switch to change between auto and manual focus?

Question

I own Nikon D7000 with 18-105mm lens. I am bit confused how the auto focus and manual focus switching works, particularly with my gear. The confusing part is both the camera and lens have an A-M switch.

I am not sure if when I have to switch to manual mode I need to shift both the buttons, on lens as well as camera? And do I have the liberty to fine tune the focus by turning the focusing ring while both camera and lens are on "A" position? Will it cause any damage to body or lens?

Here are the excerpts from lens manual:

"Manual focusing is possible even when the lens A-M mode switch is set to A. Set the camera’s focus mode to AF-S, and press the shutter-release button halfway to initiate autofocus. Next, while pressing the shutter-release button halfway, manually rotate the lens focus ring to fine-tune focus"

But that doesn't clear it up for me.

Answer 1

If you want to manually focus, best to set them both to M

• it tells the body not to try to AF, and also will allow you to take an image even if focus isn't perfect

• it tells the lens that you are manually focusing, so will allow the focus ring to turn freely

• pressing the shutter release will not attempt to focus the lens in any way

If you want to use AF, set both the lens and body to A

• however you can override the focus as described in the manual. Half-press to have AF lock in focus, then while still holding the shutter release halfway, you can turn the focus ring and adjust focus. So it's not pure manual focusing, it's just an override that might come in handy on occasion, but if you want to manually focus, set both switches to M

Having the body on M and lens on A doesn't make sense. Neither does body on A, lens on M really (but see comments), so I'd recommend you just set them both the same.

Answer 2

Based on the description from your lens, it appears your lens has what is known as FTM or full time manual focus. In an automatic focus lens, there has to be a link between a motor and the focus element. In cheaper lenses, the connection is left all the time and trying to manually turn the ring while in auto focus can and will damage the gears or the motor that drives the auto focus. The A/M switch (on the lens) manually disconnects the auto-focus motor.

In more expensive lenses, the motor disconnects from the focus elements when not making adjustments and thus you can make manual adjustments any time that the motor is not trying to make adjustments. I don't know what it is called on Nikon bodies, but on Canon bodies, you want to make sure that you are in One Shot focus mode (where the camera only adjusts the focus once and doesn't try to follow the target). On your camera body, it appears to be the AF-S auto focus mode. If you use a mode that tries to follow the target, the motor will constantly be fighting your attempts to manually focus and damage may occur.

Simply flipping the switch on the lens to M should inform the camera body that you do not wish to use automatic focus and even if the body tried to make adjustments from it's own switch, the lens would simply ignore them since the motor is disengaged from the focus element. In the event that it is an older screw-drive type lens that is driven by the camera body, then the switch on the camera body itself would tell the camera not to try driving the motor mechanically, but on a lens with the motor in the lens, I would guess it wouldn't do anything. (I'm a Canon guy, so hopefully one of the Nikon guys can confirm this.)

Personally, I love full time manual lenses and almost never put them in manual focus mode. There isn't really any reason to do so when you can get the best of both worlds. The only reason I can see to do so would be if you were unable to easily switch the AF mode to not try following focus (on my camera, it's only a button press and a wheel turn away.)

In short, it sounds like with your lens, using the camera on AF, the AF-mode set to AF-S and the lens set to A, you should be able to half depress the shutter and then make manual adjustments to the focus just fine.

Answer 3

D7000 Manual (p99) clearly states that having the lens on "M" while having the body on "AF" can cause damage to the camera. It does not say in what order the switches should be set so the safest procedure might be to turn the camera to the "off" position while setting the two switches.