Back Button Focus Explained
What we generally know since the inception of high end DSLRs, when we half press the shutter button camera focuses on subject and then we press it further to capture it. What if I would say that we have a alternate approach as well for focusing which is far better and flexible than half shutter focusing. Here we will see Back Button Focus Explained for Beginners and how to change Back Button Focus in Nikon and Canon :
Now you don’t have to half-press the shutter button to focus?
What is back button focusing :
Normally, our shutter button has 2 functions, one to lock the focus and second to capture it. In most of the DSLRs we have a dedicated button for focusing which we don’t really know or even if we know we hardly use it. We can use this button to lock focus on subject and shutter button simply takes photos.
In Nikon we have AE-L/AF-L (Auto Exposure lock / Auto Focus Lock) button as below :
In Canon we have AF-ON (Auto Focus ON) button as below :
Back button focusing just changes the way we lock focus on subject. It means now our index finger will solely responsible for taking photos whereas thumb is used to grab and lock the focus on subject. This might be seen little complicated to start but believe me it will drastically change your experience of focusing and after few moths you could think “Wish I knew this earlier ..”.
Purpose of Back Button Focusing:
Back Button Focusing can be useful for multiple reason like :
Focus holds on subject even if you release shutter button
When you remove the focusing function from shutter release button then you don’t have to worry about holding this button down to maintain focus on your subject. Many times it happens we focus on any subject and accidentally remove our finger from shutter button, this will force camera to loose the focus from subject. When we press the shutter button again camera re-focuses on subject. So with this method we always have 2 things in mind :
- Don’t press the shutter too firmly, camera will take shot whatever is in focus.
- Don’t release shutter otherwise camera again have to focus on same subject.
Now this might seems very weird to hold the focus button from thumb and then press the shutter simply to click photos. But consider this scenario of sports or child photography or on a race track. Here everything just happens so quickly that you will not get enough time to set focus and then release shutter, by that time entire scene could be changed and you will left with nothing. So when you have focusing and shutter function separately, you can just set and lock the focus and take the photos instantly.
Focus and Re-compose:
With back button focusing we can lock the focus on subject using back button and then re-compose the shot as needed, while subject stays in focus . When shutter control then focus, as soon as we re-compose the shot and focus with half shutter, camera will again try to focus on subject. This can also be done using manual method focusing mode, but that’s a all together different pain.
Its Flexible :
When we pair back button focusing with continuous focus mode (AI Servo for Canon, AF-C for Nikon), it will always result with accurate and quick focusing on moving/running subject. It is specially helpful when subject is keep running or moving. With back button focusing methods camera will automatically track moving subject and maintains the focus quite accurately and fast which will help you take the perfect shot.
We can assign focusing feature using the camera menu.
How to setup Back Button Focus in Nikon and Canon :
Step 1: Go to setting
Step 2: Scroll to screen 5 for custom controls.
Step 3: In that menu, set the shutter button to “metering start.” (Turning if OFF of AF Start is what removes the focus function from the shutter, and this is a crucial step!!)
Step 4: Set the AF-ON button to “metering and AF start.”
Its quite easy on Nikon :
Step 1: Select setting menu.
Step 2: Select “a – Autofocus”
Step 3: Select “a4 – AF activation” and
Step 4: Select “AF-ON only” and you’re done.
To summarize, below are few of the scenarios where back button focusing is superior :
- Shooting a portrait with a subject making minor adjustments to their pose between photos. You want to take a quick fire rapid succession of shots but don’t want the AF system to choose a different focus point each time you click a image.
- Race tracks, Fast-moving action or sports photos. Using a back button to focus will help reduce the lag time between half-pressing to focus and fully pressing the shutter button to take the shot.
- Situations where the AF system can get confused with what to focus on. For example, shooting through a busy road full of traffic or a net, A DSLR can change its focusing point quite easily with layers of subject are moving across. With back button focus we choose what to keep in focus and everything else will stay in the background, even if you recompose the photo multiple times.
- When you need tack-sharp images with slow shutter like 1/60 or 1/50. Half-pressing and holding the shutter button to lock focus shifts the weight balance of your hand which can cause blur in photos. Simply pressing the shutter button down fully to take the photo can reduce the camera shake effect drastically.
Few Sample shot with Back Button Focusing :
Hope I made it clear Why You Should Use Back-Button Focusing !!
Its obviously a personal choice on how we want to focus and click photos. But one should try this back button focusing technique and I am sure slowly you will fall in love with this. It saves lot of time and you will also get amazing results with fast and accurate focus specially for action and running photos.
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