View Full Version : af points

31st of December 2008 (Wed), 07:28
so when making some of the great works you guys do, what AF point settings do you use. i know with f/16 lets say you will have a fairly large DOF and the horizon doesn't have to be perfectly in focus. but there are a lot of photos that have a the foreground like a few feet from the camera in focus as well as far into the distance.

are you setting the af point to the foreground and letting the dof take care of the horizon? do you use the full af cross system? do you just use a single spot off in the distance?

7th of January 2009 (Wed), 11:05
Where you should focus to achieve both foreground and horizon sharpness depends on your focal length and aperture. Take a look at this website: http://www.dofmaster.com/dofjs.html.

The af point does not matter. In fact, you can use manual focus if your lens has distance markings.

For example, on a 1.6x crop at 14mm, f/4, you can focus on an object ~9 feet from the lens and you will have acceptable sharpness from ~4.25 feet to infinity. If you had focused on the foreground object itself at 4.25 feet, your DOF would be from about 3 feet to 8.5 feet. Stopping down to f/8 increases your dof from 3 feet to over 650 feet. At f/16, you can focus at 3 feet and you will have sharpness from 1.25 feet to infinity. At f/16, you may run in to diffraction issues though.