Hal Masover Loc: Iowa and Florida

Just got a used D850 and am looking at the Face Detection function. I prefer to use back button focus so have the camera set up that way now. I have also set the camera to Face Detection On, and AF-C mode and auto. I have two questions. 1) Is 3D tracking better than AF-C? I will mostly use this camera for weddings so tracking people's faces. 2) Once I get focus lock from the back button, do I take my thumb off that button? Will it keep tracking the face I focused on? Or do I keep my thumb down on the back button?

JeffDavidson Loc: Originally Detroit Now Los Angeles

With AF-C holding in the button will continuously focus. If you focus on a face, remove your finger from the BBF button and recompose, your original point of focus may not be in focus anymore.

Grahame Loc: Fiji

I don't have the D850 but from the manual .........................

"3D-tracking: Select the focus point. In AF-C focus mode, the camera will track subjects that leave the selected focus point and select new focus points as required. Use to quickly compose pictures with subjects that are moving erratically from side to side (e.g., tennis players). If the subject leaves viewfinder, remove your finger from the shutter-release button and recompose the photograph with the subject in the selected focus point."

Answer to your question No 1 - Firstly, with respect to your use of "better", 3D tracking and AF-C are different operations/functions. So I'll assume your reference to AF-C here refers to using this in a different AF- Area mode.

It will depend upon the difference between the reliability/accuracy of the camera locking on and tracking the subjects face in 3D-tracking mode or your ability to manually track (physically moving the camera) the subjects face in another AF-Area Mode such as 'Single-point AF' and using AF-C.

Answer to question No 2 - In AF-C (continuous) you keep the AF-On button fully depressed for all the time that you want the camera to be automatically adjusting the focus.

fredpnm Loc: Corrales, NM

I have a D850 and 750...do yourself a really big favor, check out Steve Perry's YouTube page and his own WebPage. He has an excellent book on the focusing system of Nikon cameras including the 850. It is worth every penny spent on the book.

His YouTube - https://www.youtube.com/@backcountrygallery

His Nikon Focus book - https://bcgwebstore.com/product/secrets-to-the-nikon-autofocus-system/

Hal Masover Loc: Iowa and Florida

Excellent. I just started one thing and learned something that after years and hundreds of thousands of photos on Nikon bodies I didn't know. Thanks! Ordering his book tonight. :)