Best AF technique and setting...

[splproductions]

Sorry for the multiple posts here... just trying to make sure I've got all my ducks in a row for today!

I'm shooting a toddler today and will be doing candid shots. Up until now, I've either been using the "all focus point" setting on my 500D, or more often, using the single points. I usually change the AF point to the one that is closest to the subject's eye, and then do a slight recompose before taking the shot. However, changing the point for each shot gets quite tedious.

I just read an article that said that you should use the center AF point (because it is more sensitive than the outer ones) and recompose, even if it means you are moving the camera slightly more. Is this legit advice?

Also, should I be using the "AI Focus" setting instead of "One Shot"? This article said if you subject is still but has a chance of moving, AI Focus would be better.

 

[MReid]

Single point focus on the eye. If you or the subject is moving put it on continuous focus and let it track.
Middle point focus then recompose works if you have sufficient depth of field to cover the adjustment....the closer you are to your subject and the larger your f-stop the less likely this will work for you.

If you are doing closeup up portraits, do choose the focus point closest the the eyes and recompose little or none.
I usually will plan to crop the photo in processing before I will move the focus point off the eye to recompose on close up portraits.

 

[gsgary]

Also try back button focus

 

[Big Mike]

I'm shooting a toddler today and will be doing candid shots. Up until now, I've either been using the "all focus point" setting on my 500D, or more often, using the single points. I usually change the AF point to the one that is closest to the subject's eye, and then do a slight recompose before taking the shot. However, changing the point for each shot gets quite tedious.

I don't like 'all points' because it's 'auto focus points'. In other words, the camera is deciding which points to use, not you. This is why sometimes you'll find that the camera chooses points that you don't want it to use. I much prefer to stick to the single point option.

I just read an article that said that you should use the center AF point (because it is more sensitive than the outer ones) and recompose, even if it means you are moving the camera slightly more. Is this legit advice?

That is legitimate advice, but it depends on several factors. Firstly, the camera you have. Some cameras have a better type of focus point in the middle, some don't (cross type vs linear). Often, the upgrade of the focus point is only going to work with lenses that have an aperture of F2.8 or larger...depends on the camera.

Also, should I be using the "AI Focus" setting instead of "One Shot"? This article said if you subject is still but has a chance of moving, AI Focus would be better.

One Shot will lock the focus before the shot is taken. This has pros & cons. The good part it that it easily allows you to 'focus and recompose'. The bad part is that the camera won't snap the photo until it has reached focus.
AI Servo will continue to focus at all times (when the button is pressed) and it will allow you to snap the photo, even if the lens hasn't reached focus yet. That is usually better if you know what you're doing...but it's dangerous in that you might snap the photo before it's in focus.

AI Focus, is a hybrid of those two modes. It does lock the focus, once it is achieved, but it will adjust the focus if it things the subject is moving. The problem, the camera is trying to thing again. A good photographer typically wants to do the thinking themselves, rather than letting the camera do it for them.

As mentioned, a technique that many people like, is to use back-button-focusing. Your camera may have an 'AF-ON' button, near where your right thumb sits. If not, you can go into the menu and change the * button to activate the focus, taking it away from half-pressing the shutter release. This allows you to turn the focus on or off by pressing or releasing the button with your thumb...independent of your finger pressing the button to take the photo.

 

[Austin Greene]

Also try back button focus

This is usually what I use for my wildlife photography, and it works great. A little wonky to get the hang of at first, but the freedom it allows compositionally is great. Just set AF to the middle point, focus via back button, compose as you like, then hit that shutter button. No more focus hunting every shot

Also, I always use One Shot Focus while doing back button. AI Focus is known to have some issues, and I have an irrational fear that the tiny constant adjustments of servo will render my shots not as in focus as they should be. I only use it for shooting subjects that are moving quickly enough to make refocusing a pain, unlike how some use it all the time. Personal preference I suppose.

 

[Big Mike]

Also, I always use One Shot Focus while doing back button. AI Focus is known to have some issues, and I have an irrational fear that the tiny constant adjustments of servo will render my shots not as in focus as they should be. I only use it for shooting subjects that are moving quickly enough to make refocusing a pain, unlike how some use it all the time.

Funny. The main reason I use back button focus, is that I can keep the focus in AI Servo, thus having the ability to constantly focus...but also have the ability to 'lock it' by releasing the button. In One shot, the focus is locked one you get to it...so there is little benefit to releasing the back button after that.

On the other hand, I do have to remind myself that the AF assist light only works when in One Shot mode...so when I need that, I switch.

Personal preference I suppose.

In the end...that's all it is.