Back Button Focus & the Moving Toddler :)

[In_the_Gym]

I recently came across an article regarding using the back button focus for sharper images. I completely understand using it for stationary subjects. My question is how to use it effectively with moving subjects i.e. my toddler grandson If the center focus point is used and the auto focus is set to continuous servo and I try to focus on his eyes, it seems that he would always have to be composed dead center. I use a D300s with a 50m 1.8.

Mind you, I haven't had a chance to really play with this. I was just wondering if anyone else had some other suggestions. I realize that I could change the single point to the dummy setting (white rectangle), but it seems that all I have read so far talks about using a single focus point - dead center.

Dawn

[zona5101]

generally use the center focus point...but you can switch it to one of the others and focus from there. I use the center one, it is brainless to remember and I just leave extra space to allow some room for crop changes. I'm probably just lazy because in a controlled environment, its easy enough to remember or look to see which focus point it active.
once you get used to it, you'll never switch back.

[TheMoons678]

For chasing a toddler around I cant imagine how using back button focus would be helpful. I'd just use release priority mode instead of focus priority.

I personally am just used to moving around the single point a lot, but then again I only have 11 points on my D90 instead of the 51 points that your D300 has. Why not just put it in 51-point 3D tracking mode?

[In_the_Gym]

Thanks so much for the replies I will keep playing and see what I come up with. I understand with the continuous focus on how it would be easy to use with a moving subject, just don't understand how you compose it since the focal point is in the center.

[zona5101]

Originally Posted by In_the_Gym

Thanks so much for the replies I will keep playing and see what I come up with. I understand with the continuous focus on how it would be easy to use with a moving subject, just don't understand how you compose it since the focal point is in the center.

When you let go of the back button, camera stops focusing, recompose and press the shutter. I shoot sports this way but also portraits. It really works well for portraits as I'll use the center focus point on the eye, let go of the back button, recompose and shoot. I know I don't have to keep the shutter pressed 1/2 way down and pressing the shutter won't refocus.
It took me a few weeks to get used to it. It also helps to have a battery grip with shutter/ AF button when shooting verticals.

[In_the_Gym]

Thanks so much for the replies I will keep playing and see what I come up with. I understand with the continuous focus on how it would be easy to use with a moving subject, just don't understand how you compose it since the focal point is in the center.

[Hill Country Hack]

Originally Posted by In_the_Gym

Thanks so much for the replies I will keep playing and see what I come up with. I understand with the continuous focus on how it would be easy to use with a moving subject, just don't understand how you compose it since the focal point is in the center.

I been using back button for quite a while now and can't imagine going back.

As for your question on the issue of the dead center composition with the center focus point, I agree with Zona. I leave more room in the frame to retain options for cropping. I think about the possible final crop when I am deciding how much to include/exclude in the framing. Or I will also focus with the center spot then recompose closer to how I want it still leaving some excess for cropping options. For moving targets, I leave myself space while using the center focus.

[sk66]

I don't see how back button can help with a stationary subject... I guess I can see using it with dynamic focus points for focus/recompose technique with better results.

For active subjects you also want to select a dynamic mode...9,11,21,or 51 points. Then the chosen focus point will move with the subject around those points. The more predictable the subject the fewer points I use. I also use focus priority 99% of the time. If it's not in focus, what's the point? I avoid 51pt 3D.

BTW, trying to keep focus "on the eyes" of a moving subject is about pointless. You need a deeper DOF so that the eyes will remain in focus as they move.

[zona5101]

Originally Posted by sk66

For active subjects you also want to select a dynamic mode...9,11,21,or 51 points. Then the chosen focus point will move with the subject around those points. The more predictable the subject the fewer points I use. I also use focus priority 99% of the time. If it's not in focus, what's the point? I avoid 51pt 3D.
.

I haven't have good luck with any of the dynamic settings for focus. Shooting basketball and soccer it would sometimes focus on something I didn't expect when I was tracking one kid through the action so I took that option away from the camera and I pick. But I know you shoot a lot of wildlife and other moving things so coming from you means I need to reevaluate and see if it was my technique that was the root of my issues.

[sk66]

Originally Posted by zona5101

I haven't have good luck with any of the dynamic settings for focus. Shooting basketball and soccer it would sometimes focus on something I didn't expect when I was tracking one kid through the action so I took that option away from the camera and I pick. But I know you shoot a lot of wildlife and other moving things so coming from you means I need to reevaluate and see if it was my technique that was the root of my issues.

Depends on the camera....
Lower end models like the D90 have big issues with this and they don't have the menu setting to modify the behavior.
On all of the models I've owned (D200/300/3/7000) there is a focus delay setting in the menus..(I use it so much I insist on it). This tells the camera how long you want it to wait before refocusing on something "new" in the FOV.