Focusing tips
Focus lock
We’ve all been in the situation when we know what we to focus on but, for whatever reason, our cameras have another idea. Maybe other subjects around or in front of the intended one are distracting it, or the camera keeps losing focus on account of the subject being too featureless or low in contrast for it to always be noticed.
Or perhaps we’re shooting through a window and the camera keeps focusing on the window itself rather than what’s visible through it.
Your camera’s focus lock feature is a fast way to ensure the camera stays locked on the subject of your choice.
Once the camera has found focus, pressing the relevant button will temporarily disable the focusing system so that you the camera literally stays focused on what you want, leaving you free to slightly recompose the image and know it won’t get distracted.
This technique also helps when a focusing point does not cover the subject after you’ve recomposed the image. You could, of course, simply use manual focus to get around any issues with the autofocusing system, although this way you retain both the speed and accuracy of autofocus.
Back-button focusing
Most of us are familiar with the idea of a camera focusing on a subject with a half press of the shutter-release button and capturing the image when the button is fully pressed down. This is perfectly suitable most of the time, although focusing using a separate control can be beneficial in some situations.
On Nikon and Canon cameras the button that does this is marked AF-ON, although some Nikon models that lack this can have the feature assigned to the AE-L/AF-L button.
By disengaging focus from the shutter-release button, you can focus in advance and know that the camera won’t hunt around when it comes to the critical moment of capture.
This is particularly useful whenever you’re in a situation when something may be moving around the subject, which may cause the autofocus system to refocus.
It also means you can focus and recompose with greater ease and also allows you to subsequently override the AF system with manual focus if you feel you need to, with the knowledge that pressing the shutter-release button won’t cause your camera to refocus.
AI Focus / AF-A
Most people are familiar with the separate focusing modes for still and moving subjects. Canon’s DSLRs, for example, have long offered One Shot and AI Servo settings, while Nikon and Pentax models offer AF-S (single) and AF-C (continuous) options.
You may have noticed, however, that some camera offer a third option is often included alongside these, labeled AI Focus on Canon DSLRs and AF-A on Pentax DSLRs. So what do these do and when might you use them?
These options automatically switch between the two primary options as and when a camera deems it necessary. So, if you’re focusing on a subject and it starts to move, this option will notice this and will attempt to keep track of its movement.
This is useful when capturing any kind of subjects that are prone to unpredictable movement, such as children or pets, or even when focusing on a single person in a crowd or in the distance.
Disabling the AF assist lamp
Many cameras have a small lamp on their front that sometimes springs to life to illuminate a subject, and its purpose is to help out the camera’s autofocus system, particularly in darker conditions.
This can be useful when capturing inanimate subjects, although there may be times when it’s not welcome, such as in places of worship or any other occasion where you need to be discreet.
Fortunately, you can disable this through the camera’s menu system. While this will obviously have an impact on your camera’s ability to focus in low light, it will help you to stay discreet when you need to.
AF Microadjustment
Cameras and lenses are assembled with great precision, but they are designed to fit within a certain level of tolerances. This, together with the general bumps and scrapes that equipment encounters through use, means that different combinations of camera and lens can give different results when it comes to focusing.
It’s no wonder, then, that many manufacturers have provided the option to tailor how a lens performs on a particular body in the last few generation of their cameras.
These adjustments, which allow you to very slightly adjust focus if you find the camera is consistently focusing a little in front of or behind where it should, don’t physically affect the lens itself, rather they happen in camera and only apply when that model of lens is used (unless you choose to apply it globally for all lens, which some cameras allow you to do).
Many lenses should be fine and it’s possible that you won’t be able to improve on this, but if your camera offers this and you do attempt it, make sure to follow the instructions in your manual to get the best results.
Touch focus
If your camera has a touchscreen it’s very likely that it will allow you to focus on a subject simply by keying it on the LCD screen. This is great when the subject is particularly small or at the peripheries of the frame, although it’s also great for any kind of tripod-based work where you may be using the LCD screen instead of the viewfinder for the purpose of composition.
It may also be possible to combine this with the option to trigger the exposure, which can speed up your shooting.
Focus peaking
A feature on many CSCs and some compacts, but also starting to make an appearance on DSLRs, focus peaking gives you a much clearer idea of when your subject is in focus when using the manual-focus mode.
Here’s how it works: as you adjust your focus manually, highlights start to show over areas that are in focus.
The more in focus a subject is the more covered it is in highlights, and when you’ve reached the maximum amount over the desired area you know you’ve reached the most appropriate position. This option is great for tripod-based work, where you can adjust this with utmost precision.
