Hi again, a discussion in one of my blogs, made me think about focus, it’s is one of these discussions that pops up once in a while. At first glans it’s a really easy choice, manual or auto… what can be so complicated about that!
What about terms like “toggle focus,” “focus and recompose” and “back-button focus,” are you on top of these, do you know what it brings to the table? In In this blog, I am going to try to break down the concepts for you!
It is no secret that I am a truly in love with my A99V, and as such is totally biased. I am sure the concepts are applicable on other platforms as well; I just don’t care enough to write about them J
Auto focus system
Back in time when I decided on my A99V, one of the features that took my interest was this new “highly advanced Continuous AF mode uses 19 AF points with reliable depth-direction focusing performance to steadfastly capture subjects and is strongly assisted by the 102-point multi-point focal-plane phase-detection AF sensor”… WOW, only it turned out to be a brilliant marketing feature, which I will most likely never get to use as they do not support my old beloved glass, but only a few AF-D lenses. Old lens users like me are left with the conventional 19 point AF sensor system, no “depth map assist” function for us, and the AF Range Control cannot take advantage of the 102 point depth map display… bullocks!
Manuel or Back-Button Focus
I really like doing things myself, this include the settings of my camera and focus. For me EVF focus peaking combined with magnification is my preferred method, it is an almost flawless combo only challenged by fast moving object, shooting wide open which most likely require AF.
But when I shoot AF, I shoot in a mode allowing flexibility, and it’s here Back-Button Focus (BBF) comes in. Do note that BBF is not the same as back-focus, BBF is exactly what the name implies, an option to change how autofocus is activated. Instead of AF being activated by the shutter release button, Auto Focus is activated by a separate button on the back of the camera. So what’s the hype about, well it’s about no more switching your lens to manual focus. Even with your lens set to Auto Focus, you can manually focus and not have the camera unintentionally refocus when pressing the shutter button.
Give me a reason why BBF is any good.
Should I give a breadwinner for BBF, then it would be control and convenience. Being able to hold that AEL and Focus when recomposing is exactly what I want in many situations. The ability to combine BBF with object tracking just adds to the convenience.
I guess that does just fine… give me some practical examples…
Imagine you are shooting a scene, a group of dears in the forest, and a branch sways in front of your lens. And focus starts slowly to hunt, making you miss those moments where the motive was at its best. Back button focus would have saved the day, as you would still be shooting sharp shoots and the branch would have been of less importance.
Imagine that you are shooting portraits. The person who you are shooting is standing still and you want to take several different shots with varying composition of the person. You have your focus point on the persons eye, then recompose the photo, moving the focus spot to the correct spot, focus, and then take the photo is going to be some job.
I guess among the many reasons we have to shoot in Manuel is the inconveniences autofocus introduces. With BBF a lot of these inconveniences are killed off, does this mean that we should be shooting automatic from now on… no, but I am sure we could get rid of a lot more trivial work when shooting day by day.
How to set back-button Focus on Sony Alpha A99V
(SLT-A99V camera firmware to version 1.02)
Firstly, you need to disengage the focus and AEL from the shutter button. The idea of back button focus is that the focus and shutter are independent so you don’t need to half-press the shutter to focus.
MENU → (Camera Settings 4) [AF w/ shutter] → OFF.
MENU → (Camera Settings 4) [AEL w/ shutter] → OFF.
Now will the camera no longer auto focus/ or AEL when you half press the shutter.
We want the AF/MF button, and we want to set it to AF On.
MENU → (Custom Settings 4) → [AF/MD Button] →AF ON.
If you have trouble getting this to work, make sure that your Eye-Start is off
MENU → (Custom Settings 1) → [Eye-Start AF] → OFF
Another handy setting is having the View Finder focus peaking set to on
MENU → (Custom Settings 3) → [Peaking Level] → High
MENU → (Custom Settings 3) → [Peaking Color] → Red
Finally make sure you got AF-C on
Fn button (Focus Mode)
That’s it. You can now use the AF/MF button on the back of the camera to engage focus, rather than half-pressing the shutter button.