Using manual focus

While I rely heavily on Autofocus most of the time, there are still occasions when I switch my camera over to Manual Focus. For moving situations, Manual Focus is sometimes faster than Autofocus for the simple reason that as good as your autofocus system is, you are still smarter than it is. If you are in a situation where a moving object is traveling in a very predictable way, then you might be able to track focus manually very smoothly as you wait for the precise moment that you want to shoot. Your autofocus system may rack in and out of focus as it looks for the point.

Manual Focus is also useful for times when Autofocus doesn't lock, either because your subject lacks contrast or because there is not enough light in the scene to focus. Of course, if there is not enough light for your camera to focus, then there may not be enough for you to see either, but that's still worth a try. Finally, I sometimes use Autofocus and Manual Focus in combination. If I'm shooting the same subject over and over, for example, if I'm shooting a landscape in rapidly changing light, I will frame my shot and Autofocus--or using Autofocus--then switch the camera to Manual Focus.

As long as I don't bump the lens, my autofocus choice will now be locked in. Now, I can just keep shooting without having to wait for autofocus. This can also be handy for a portrait shoot where your camera-to-subject distance never changes, and you want to be able to shoot without waiting for focus. There are two ways of selecting manual focus on the D800. Which one you will use depends on the type of lens you have. If you have an AF-S lens, then you will use the manual switch over here on the side of the camera. Right now, I am set to Autofocus.

I am going to just switch that over to Manual. If you are using an AF lens, then you'll use the Focus mode switch over here on the side of the camera. It's a rocker switch and a button, and I just flip that over to Manual mode. I am not going to do that here because I'm using an AF-S lens. That brings us to a very important point, which is spelled out on page 101 of your D800 manual. There is a box about AF-S lenses. It says "Do not use AF-S lenses with the Lens Focus mode switch set to M,"--that is, the switch on the lens--"and the Camera Focus mode Selector set to AF." That's the one on the body.

"Failure to observe this precaution could damage the camera or lens." That is, if you are using an older AF lens, you want to be sure that both the lens and the body are set to Manual Focus. Once I'm configured for Manual Focus, I just use the Manual Focus Ring on my lens. Some lenses will have markings here that show the distance that you are focused at, usually in feet and meters. Now, you may think, "Oh! Good, I can be really precise about focus. I will measure the distance from my focal plane out to my subject." Well, the problem is these are pretty blunt instruments, in terms of gauges, so you're not going to really be able to dial in a very precise number here.

However, the camera can help you with your autofocus. It's got a cool feature where, even in Manual mode, the autofocus mechanism will double-check your manual focus. The way it works is, you put a focus point on the subject you want to focus on. So, in this case, I steered it over to the camera on the left. Now, as long as I keep half-pressing the Shutter button, while I turn my Manual Focus ring, it will light up one of two arrows indicating which direction I need to focus, and when I get focus set properly, it will show the circle that indicates that I have got focus.

So this is a way of having the camera double-check my focus. If you think you've got good manual focus, put the focus point on the thing you want to focus on, half-press that Shutter button, and if you see one of these two arrows, then you know that you're off, and it's telling you the direction that you should go. At that point, you might be better served simply by going back to Autofocus. If the camera can figure it out for you, then you might as well use the Autofocus mechanism. But as I said earlier, there are still a lot of good reasons to use Manual Focus.