Not too long ago we had a discussion about focusing. I was asked to explain the reasons for why I do what I do, and I figured I could write it up in another blog post.
Note that my ways are not written in stone. It’s not the holy grail. It may not the be the “best” way for everyone, even if I feel for me it works best.
I’m a Nikon shooter, so the images and descriptions you see here are based on Nikon DSLR bodies (the example(s) I used are from D700 and D800). I’m positive Canon has similar functions, but they may be named differently and be located in different places in menu and on camera body.

So focusing…

Manual or automatic?
It depends, I guess. Some swear by manual focusing, some swear by auto-focusing.
If the circumstances allow it, and the focus points reach where I want to focus, I will use auto-focus. If not, I’ll use manual focus. If your camera body and lenses are properly calibrated (it’s like with your computer screen, you also calibrate that every month, right? RIGHT?? 😉 ) the camera will do a better job than you do (remember I said “if the circumstances allow it”).

In the menu of the camera you can set the amount of active focus points. I’ve set it to 21. 9 is too little and believe me, you do NOT want to be scrolling through 51 focus points all the time. 21 is a good average and it keeps -as I call it- custom focusing quick and easy.

Set the amount of active focus points in the menu of your camera

With the disk on the back of the camera you can select which focus point you want to use for focusing. Look through you view finder of the camera to see which focus point is currently active.

With the big round disk you can select the focus point (check in the viewfinder or -with some cameras- on the top display).

If you have a vertical grip, there will be a second disk or knob with which you can select the focus point while you’re shooting vertically.
And yes, I’m a cheap-ass Dutch guy. I use a third party vertical grip, because I refuse to pay the ridiculously overpriced amounts that Nikon is asking for their original battery packs. It doesn’t do anything more than give you one or two frames extra when you’re burst-shooting in jpg. And the batteries are already a wringer as it is, let alone the batteries for Nikon’s battery pack.
If you want to have an excellent substitute: On the D700 I have a ZEIKOS, and for my D800 I just recently bought a Phottix. Both work great, look and feel solid and do exactly what I need them to do. And that for about 1/5th of the price. Nikon can stick their battery packs …. well… never mind.

Shutter button focus or back focus?
I don’t think that’s a matter of “I guess”. This is -to me, at least- a no-brainer. If you’re an enthousiast (or worse, a pro) photographer, you’re shooting daily, you’re focusing by pressing the shutter button half way all the time and you’re NOT annoyed at least every time you press the shutter, you are either the most patient, agreeable and forgiving person in the world, or there’s something wrong with you. When I started photographing, looong time ago, in a previous Life, I started with my dad’s old Mamiya. It was a full manual. When I bought my first SLR camera with auto-focus, it came with that shutter-button-half-way-press-focus-thingy. And it annoyed the crap out of me already from the start. And that was the time that you couldn’t switch it off yet. You just had to live with it, or -like I did most of the time- switch back to full manual.
I get it that the manufacturers put it on the consumer cameras. If you don’t know anything and you just make snaps of your kids or your holiday it works just fine. But why they put the function on pro-sumer and pro bodies is completely beyond me.
Do yourself a favor, scroll through the menu, switch off the focusing on the shutter button and start focusing with your thumb on the back of your camera body with the AF-ON button.

Menu A5 on a Nikon D700 (A4 on a Nikon D800, A6 on a Nikon D200) will give you the choice to set focusing on the shutter button AND the AF-ON button or on the AF-ON button only

The AF-ON focus button on the back of a D700/D800

Why?
The most annoying thing about the shutter button focus is that you have to focus every single frigging frame (unless you want to keep the AF-L button pressed with your thumb, in which case you can just as well use the AF-ON button), even if you don’t change position or composition. It just is that way. You press the shutter half way, you focus, you press the shutter all the way, you take the picture. You let the shutter go and you have to go through the whole process again. In “normal” circumstances you can’t take a picture without having to (re-)focus, because you will always press the shutter half way on your way to taking a picture by pressing the shutter all the way – if you get my drift. When you use the AF-ON button to focus, you need to focus only once and you can take as many pictures you want of the same subject without having to re-focus. It saves time, battery power, frustration, head-ache and finger-power (do you know how many muscles you use in your fingers when you have to keep that damn button pressed half way until you lock focus? – I don’t either).

Some cameras won’t let you take a picture unless you lock-on focus. Truth be told, one could wonder why you want to take an out-of-focus image, but hey… if you need to take a quick picture (imagine Kate topless or something) and focus isn’t the first priority, you can’t be stuck with having to search focus, because your half-way pressed shutter and not-yet-locked-focus is preventing you from taking that money-shot.

Should you use the method of focusing on a scene and then recomposing it to get your subject in a different position in the frame (a little bit about that further down this post!), it’s also easier to use the AF-ON button. Sure, you can use the AF-L button, but then first you have press that wretched shutter button half way down to focus, then fiddle your thumb to the AF-L button -which, at least on the Nikon body, sits just about half a centimeter too far to the left to comfortably do that (and I have long fingers!)- without letting go of the shutter and losing your focus or having to refocus, recompose your frame and then press the shutter all the way… As opposed to press the AF-ON button to focus your scene, let go of the button, recompose the scene, press the shutter. Doesn’t that sound just so much more relaxed?

And then there’s of course the people who shoot moving subjects. Have you tried shooting a burst of shots, following the moving subjects and keeping focus on while your subject moves a bit out of the focus area you set while pressing the shutter button half way? You’re screwed, I tell you. It’s impossible.
The beauty of the AF-ON button is, that you can keep it pressed while you follow your subject and you keep the focus locked on your subject while it moves towards you or away from you. That may not work exactly 100% if your subject moves with a speed your camera can’t keep up with, but typically it works very well.
For this you do need to check another little setting on your camera:

Focus settings button on the D700/D800: C = continuous, S = single, M = manual

Set your camera on C for continuous servo, meaning it will keep on focusing on the selected focus point as long as you press the AF-ON button (or the shutter button). It’s said to use this setting only for sports and actions, but I have it set like this all the time. You never know when you land in a situation where things go quick, and it doesn’t otherwise make any difference.

Recomposing a shot
I shortly mentioned this earlier.
Many people use this method to make their pictures. They don’t use the moving focus points, but they have the focus set in the center of the view finder. They focus on a subject, keep the shutter button half way pressed to “keep the focus locked” and recompose the shot to, for example, abide by the rules of thirds. Or another method, they focus on a subject, use the AF-L (focus lock) to “lock on the subject” and recompose the shot.
But here’s the thing:
There’s a general misconception about focus locking. Most people think that when you lock focus, focus is locked on the subject. That’s not true. When you lock focus, you lock focus on the location where your subject is/was when you locked on. If you recompose by rotating your camera or body slightly away from the subject to put it in a third of the frame you change the distance from your camera to the subject and thus you change the focusing distance. This means that, however slightly, your subject is no longer in focus.
Below is a (very crude) drawing of what exactly happens when you recompose an image. The green and the red line are equally long, showing that the distance from the lens to the subject has increased slightly after recomposing the image.

When you recompose an image after focusing and rotate the camera (or your full body) slightly to get the right framing, the distance between lens and subject increases, and thus -however slightly- throwing the subject out of focus.

Most people probably won’t even notice it and of course this theory is subject to a lot of variables, but if you’re critical about your focus, it’s best to move around the focus point in your viewfinder and compose with the focus points on the subject in the composition you want, and not recompose.

Always interested in hearing other people’s opinions.
Share what you think!