10 December 2018
KEEPING FOCUS

Today’s blog is going to move away from the elements that work toward getting the correct exposure that has been the subject of this series up until now and look at an arguably even more important aspect of photography, and that is none other than the camera’s focus – the essential mechanism that allows us to get clear, sharp wildlife images.

Why do I consider it more important than exposure you may ask? Well, the fact of the matter is that if you get the exposure a little wrong, you can always improve on it and correct it in post-processing; but, if you fail to get a sharp image, there is nothing you to do to magically “un-blur” your image! It is because of this that this blog post is going to go through the process of understanding how best to use your camera’s focusing systems to achieve those clear, sharp images.

 
Modern day cameras allow you to achieve excellent, clear, sharp images, such as this portrait of a female leopard.

Just as the modern-day cameras have made metering and exposure so much easier for us as photographers, the camera's built-in, intelligent focusing systems have revolutionised the ease with which we can all now get pin-sharp images of not just static subjects, but of fast-moving ones too! If anyone started their interest in photography a couple of decades back, you most probably learnt the frustrations of using the manual - focus mode on those cameras, and probably got even more frustrated trying to use their auto-focus systems too; as old professionals used to exclaim: “I can auto-focus quicker with my eyes and hands!”. Luckily, the times have changed, and today the focusing systems on all DSLR cameras are such that is almost unheard of for people to still be using manual focus for ones’ general photographic needs. That being said, manual focus is still available for those wanting to use it in tricky focusing situations (such as a leopard poking its head through a clump of grass), and can be activated by selecting this option on the lens. For 99% of other occasions though, it is best recommended to keep the lenses’ focus set to auto.

The camera’s auto-focus system allows one to capture animals in motion far better than manual-focus systems ever could. 

When it comes to taking control of the camera’s focus systems, there are two main elements that need to be understood:

* the selection of the focus point(s)

* the focus mode

Camera’s today vary greatly in their focus systems, and generally speaking as the models get bigger so too do their auto-focus systems – not only in terms of their speed and performance, but also with regards to the number of focus points that they have available.Entry level models typically have nine focus points, whilst the higher end models have many dozens of AF - points (Nikon’s flagship models boast 153 AF- points!). The more focus points one has, the more control one has over exactly which part of the scene is being focused on, and how well the camera will auto - focus as the subject moves across the array of focus points.The focus points also vary in their performance depending on whether they are geared towards finding focus on only vertical or horizontal lines, or both – the latter are known as “cross-type” focus points that are sensitive to changes on both vertical and horizontal axes. Many camera’s only have these very accurate cross-type sensors at the centre focus point, whilst on other cameras, AF -points only function as cross-type sensors when used with wide-aperture lenses–it is best to consult the camera’s user manual to find out more about which focus points are cross-type. 


An image showing the focus points available on the Canon 5DmkIV, as well as which focus point was used to focus on the rhino (the red block).

Irrespective of the number and types of focus points that your camera has, there are two main ways of selecting which focus points get used when focusing on a subject:

* automatic focus point selection

* manual focus point selection

In automatic AF-point selection, the camera decides which part of the scene it should focus on using the information gathered from all the focus points, and then it decides which point to use. For animals that are standing out against a nice, clean background this works perfectly. Likewise, a bird perched on an open branch with clear blue skies behind it will pose no problem for the camera’s automatic AF-point selection. However, put a leopard in the long grass with twigs and branches in front of its face, and the automatic AF-point selection is going to quickly lose its place on your Christmas card list! The camera will not be able to differentiate the subject from the surrounds and will invariably end up focusing on a nearby branch, leading to an out-of-focus subject, and a very frustrated photographer.


With a clear background, it is very easy for the camera’s auto focus to pick up the subject, like with this carmine bee-eater against a blue sky.

For this very reason, my personal preference has long been to manually select the focus point that I wish to use rather than letting the camera decide for me. This allows one to accurately focus on the very point that they want to focus on, and not some other random point in the scene. In addition, because the centre AF-point is also usually the most accurate of the focus points, this is the manually selected focus point that I opt for. One potential problem with this approach is that if one always uses the central focus point (it is often the case with many entry level cameras that only have a central focus point). You end up with poorly composed images, where every image has the subject in the middle of the frame; as we will see in later blogs, compositionally speaking, this is one of the least desirable positions to place your subject in.


By using just the centre focus point, I could accurately focus on this leopard through the vegetation, then recompose and get the image – something that would not have been possible with the auto AF-point selection.

So how do you get around having the centrally composed subject? Well, you could opt to use one of the other AF-points closer to the subject, but if it is not a cross-type sensor, it may not focus as easily and accurately. A better alternative is to set your camera to single - shot focus - One Shot (Canon) or AF-S focus mode (single shot auto-focus on Nikon)- and use your central focus point to ensure accurate focus. Once focus is locked, you can recompose the image with the subject off centre and click away. This is done by positioning the centre AF-point over the subject and half pressing the camera’s shutter button to begin the auto-focus. When focus is achieved, the auto focus point will illuminate (or the camera will beep but please, for wildlife photography, turn that beep off!!!) to let you know that focus is achieved.Whilst keeping the shutter button half - pressed down, and you can now move the camera around as much as you want, but it will not attempt to refocus (important: this only works in One Shot or AF-S modes). When you have re-positioned the subject in the frame, press the shutter button the rest of way to take the photo. After you release the shutter button the focus lock is released too, and you can carry on as normal. If you wish to take another shot of the same subject, you can repeat this above process. This above method works well enough for static subjects, such as a leopard sleeping in a tree or a pride of lions resting in the riverbed; but what happens if these cats suddenly wake up and get active?

It is easy enough to get a sharp image of a static subject, such as this lioness standing still, using the camera’s single-shot focus mode.

To begin with, if you are using single - shot focus that locks focus on a sleeping lion 15m away that suddenly gets up and comes walking towards you, then that focus remains locked at 15m and you click away happily until you see the results; a lovely spot of sand that is beautifully in focus, and a lion that gets blurrier as it walks towards you! For this very reason, the auto-focus systems have a continuous focus mode known as AI-Servo(for Canon) or AF-C focus mode (continuous auto focus in Nikon). In these modes, when the shutter button is half-pressed down, the camera’s auto-focusing kicks in and will it keep on focusing and adjusting for the movement of the subject; because it is continually focusing, there will be no beep or flashing focus points once focus is locked, as focus doesnt lock in this mode.


A series of a herd of elephants moving straight towards the camera, where every image is sharp and in focus thanks to using the continuous focus mode.

Going back to the above example; once the sleeping lioness wakes up and starts walking towards you, you need to switch to continuous focus so that as she is walking towards you, the camera is anticipating her movements and continuously adjusting focus to ensure that she stays perfectly in focus as she does.This continuous focus works wonderfully well whilst she is moving, but what happens if she lies down again?With continuous focus on, you point the centre focus-point over the sleeping lioness’s face and half-press the shutter to focus on it; but, you don’t want a central composition, so you move the lioness within the frame to recompose.Whilst your finger is half-pressing the shutter button, the continuous focus is going to keep on refocusing on whatever is now in the centre of the frame, and because she has been shifted off-centre, it won’t be the lioness! 

How do we get around this problem now? There are a number of options, each with their own pros and cons:

* Firstly, you could manually change between single-shot and continuous focus modes, but this invariably leads to missed opportunities whilst changing focus modes.

* Secondly, you could make use of the camera’s automatic focus-mode detection known as AI-focus (Canon) or AF-A (automatic auto-focus in Nikon); in this mode, the camera will determine whether the subject is static or moving and automatically switch between the single and continuous focus modes.Although this sounds good, in practice it is not always as responsive as we might like...and there are better alternatives!

* A third option would be to stay in continuous focus all the time, and rather than only using the central focus point, you could manually select the focus point that is closest to the subject; in this way, even though the camera is going to be constantly focusing, the focus will always be on the subject.The problem comes in if the subject is not close to the focus point you desire, as well as the fact that many of the peripheral focus-points are cross-type sensors.

Lastly, change the way you focus!It is a bold move, but it one of the most beneficial changes that I made as a wildlife photographer to counter the problems that I continuously encountered whilst trying to find a solution to the above problems.The answer I found is called back-button focusing.

*As cameras’ have always worked the same, we have become accustomed to focusing using the shutter button –half press to focus, press all the way to release the shutter and take the photo.

What back-button focusing does is to separate these two functions and dedicate the shutter button to shutter release (and exposure lock) and reallocate the focusing button to one of the buttons on the back of the camera (depending on which camera model you have, the button will be different). Sounds simple enough, and once you get rid of the natural desire to focus with the shutter button, it is...but that is not the reason that we make this change!

In moving the focus function to a back button independent of the shutter, it now means that we can press the shutter to take photos as often as we want, and it will not attempt to focus on anything. If you recall from the issues, we experienced with continuous focus, you will see that we now have a solution to our problems!If we revisit the situation of the sleeping lioness that suddenly gets up and walks towards using back-button focusing instead, we will see the benefits. 

Once the back-button has been programmed to focus (my preference is that the camera focuses when the button is pressed in, and stops when you release it), I set the camera’s auto-focus mode to continuous focus.With the lioness sleeping in the riverbed, I point the centre focus point over the lioness and press the back button to focus; as it is in continuous focus mode, it won’t beep and lock whilst I am pressing the button (as it would do in single shot focus). When the camera achieves focus on the sleeping lioness, I release the buck button focus and it stops focusing, I can then recompose the image and when I have a composition I like, I can press the shutter button to take the picture. Even though I am in continuous focus and the centre focus point is no longer over the lioness, as the shutter button no longer controls focus, it will not try to refocus, and it will simply take the photo with the focus I want!


With this static lioness, I focus on her face, release my finger of the back button focus button, recompose and can click away without worrying that the continuous focus mode will keep on attempting to focus on something (that would now be the background); when I click the shutter to take the picture, the camera does not try to refocus.

The lioness now stands up and begins to walk in my direction; in the past this would have required me to put my camera down and switch to continuous focus mode.Now, with back-button focusing set to continuous focusing. I don’t need to drop the camera from my eye to change the setting; I simply push the back -button focus button to continue focusing on the lioness that is now walking towards me.Pressing the shutter will take the images as she approaches. If she suddenly stops moving; I can focus on her, release the back - button focus to stop the continuous focusing and take pics of her in a stationary position with the focus “locked”. When she moves again, I simply push the back -button focus to carry on focusing on the moving subject!Sounds great, doesn’t it? Yes, it takes a little bit of getting used to, but once mastered, it will revolutionise the way that you are able to take advantage of the modern cameras’ auto- focus systems and greatly improve your hit -rate with moving subjects and action shots. Whilst explaining how to set up your back -button focusing system for your specific camera is beyond the scope of this blog, you would be able to find out how to do this on any number of websites out there, and then you too can start experiencing the benefits of this new way of doing things.


As the lioness gets mobile again, I press the back button focus button to resume the cameras continuous AF system, and the camera will automatically adjust the focus taking into account the subjects speed of movement, and I can click away using my shutter button allowing all images in the series to come out perfectly focused.

That is that. A little overview on how camera's focus and how to get the best out of them. I trust that you will enjoy playing around with the different settings and options to see what works best for you. 

Until next time, happy shooting (hopefully, with some sharper images!)

Cheers

 

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