Of all technique-related issues, focus is the one that seems to baffle the most people. Here's an extract from a typical email in my inbox:
'I use 'budget' lenses - 70-300VR and 18-55 - and of course I know that they're not sports lenses and slow AF costs me critical focus. My main problem is subject out of focus. How to track the subject, where to put the focus point, how to use dynamic focus etc.'
Pictures that aren't sharp are a source of disappointment. And of course, unlike images that aren't exposed quite right or have out-of-whack white balance, there's not much you can do to rescue an out-of-focus shot. So here's my guide to getting your cycling shots nice and crisp:
1. Read up on the theory
Here's the thing: you can't expect to cajole your camera into delivering in focus images until you understand the basics. And by that I don't mean the difference between dynamic and single point AF - I'm talking brass tacks. D'you know the difference between depth of field and depth of focus? No? You should (and no, I'm not going to go into that here - there's plenty of good info out there if you look for it). You also need to understand how aperture, focal length and subject distance affect depth of field - and the best way to learn is to practice. Use a static subject (preferably one that won't get up and walk away when it gets bored) and take a series of pictures at different focal lengths, apertures and subject distances. Take notes. Have a good look at the resulting images.
And if you think that sounds dull, you'll love what I'm going to suggest next. I know photographers - myself included - who've consulted the depth of field tables that most lenses come with to figure out how much (or how little) leeway for focus errors there might be at a certain aperture / focal length / subject distance combination. Sometimes those details matter.
Shot on a 200mm f/2 wide open: the lead riders' handlebars and face are in focus; the saddle isn't. Can you say 'shallow depth of field?' No matter what lens you use, there will be some situations where your focus has to be absolutely precise. Know what they are... then you can work out how to get around them.
2. Switch the AF off
No, really. I was going through a wide selection of pictures for this feature and I had to try really hard to find a handful that demonstrated autofocus in use. I use manual focus (or, more accurately, pre-focus) perhaps 98% of the time despite owning cameras with extremely effective, state-of-the-art AF and lenses to match.
There are a couple of reasons for this:
- AF is far from infallible. Simply put, don't believe the marketing hype. No matter how many AF points your camera has, how customisable the AF system is and how fancy your lens, it's all just a bunch of dumb ol' algorithms shunting ones and zeroes around. And in the case of cycling, AF can sometimes have a hard time coping with all the holes in a bike-and-rider target, resulting in a crisp background and fuzzy rider. Oh, and that's before you start nitpicking about whether you focus on the handlebar or the rider's head (see the pic above).
- Most of the time, you don't need AF for cycling. Why? Because unlike, say, footballers, cyclists tend to follow fairly well-defined and predictable paths. If you know in advance where you're going to take the shot, the rider isn't head-on and you're not using a particularly long lens with a tight crop, you may be better off wresting control back from your camera.
So how do you focus? You need to pre-focus on the spot where the rider will be when you snap them. It's not hard - just focus on a patch of grass, a rock, a tree... anything that's about the right distance (hint: depth of field extends roughly one third in front and two thirds behind the plane of focus. So if you're going to err, err on the side of front rather than rear focus).
How you go about this depends on your camera and personal preferences. I have my cameras set up so that the AF is activated only by the dedicated AF-ON buttons on the rear, and my lenses have built-in motors that can be over-ridden at any time by twisting the focus ring. So I can blip the AF-ON button to focus on my selected spot, then simply leave alone. If I need to adjust it I can either blip the AF-ON button again, or use my eyes and the focus screen and twist the focus ring on the lens.
Not all cameras can be set up this way, but there's always an alternative. You can focus entirely manually or use the AF and then lock your focus point. As always in these cases, best to RTFM.
Here are a few examples of pre-focussing in different scenarios:
Wide lens, bright light: small aperture, loads of depth of field. It's hard to get things wrong in this scenario, but I always set and keep checking focus on the point where the shot will be taken anyway. This is the closest a bike photographer will get to using the hyperfocal distance technique that's the mainstay of the sharp-from-foreground-to-background school of landscape photography, though I'm not at all bothered if the background is out of focus - it'll likely be a bit blurred from movement anyway.
Middling telephoto lens, low light: wide aperture, limited depth of field. When you know where your rider's going to end up, there's no reason not to pre-focus. Hint: for jump shots the peak action takes place somewhere between the take-off and landing lips, so you sometimes need to focus on something that's at an equivalent distance. Takes a bit of trial and error to get right, sometimes.
Long lens, tight crop, low light: wide aperture, very limited depth of field. In this kind of sunlight / deep shade scenario, even the best AF systems are more likely to come unstuck than not. And, once again, there's really only one place that the shot will work. So focus there and concentrate on getting the timing right.
3. Figure out when AF will do the job better
Sometimes, in spite of its shortcomings, AF is the better - or possibly only - way to get the shot. Experience will tell you when this is the case, but if you've tried and failed to get the shot manually it's often worth giving AF a shot. As a rule of thumb, the following situations are worth trying with AF:
- head-on and fast-moving rider, with
- long lens and, possibly
- a sequence
One of the reasons I dislike AF is that the position of the AF sensors tends to dictate rather central compositions, which often aren't what I'm after. But many cameras have outlying sensors that allow a bit of scope for creative composition - and anyway, in a few situations you may have no choice.
Long lens, bright light, fast moving head-on rider, sequence required: it's an AF no-brainer. You might get a single sharp shot if you pre-focus and your timing is good (and in the old days a really good sports shooter might be able to follow-focus manually), but the AF is far more likely to turn in a decent result.
Long lens, slow-moving climbing rider: not an obvious candidate for AF. But climbing shots are all about getting the timing right. Sometimes it's easier to crack off two or three shots around the peak action, which makes it hard to pre-focus and get the timing right. So I switched the AF on and shot a short sequence, of which this was the best.
Long lens, low light... but sequence needed. Some tricks happen so fast it's almost impossible to time a single shot with any reliability. I knew I wanted a mid-whip shot, but focussing manually just wasn't going to do the job. So I used AF and a brief burst of 9fps to get the shot I wanted. AF in these conditions can be tricky for the camera, and it takes some experimentation - and a bit of luck - to find the setup that works best. As a rule, the more AF points you have active the more work you're asking the camera to do, potentially slowing focus responses.
4. Learn to tell the difference between out of focus and blurred
They're not the same, particularly when you're dealing with a moving subject. Not-quite-sharp pictures are the biggest issue I have to deal with on my photo courses. Indeed, I'd go so far as to say it's one of the things that separates the really good pros from, well, everyone else. But there's not always a single reason why a shot isn't sharp, and one of the most useful techniques you can learn - and I'm afraid it just does take time and experience - is to differentiate between focus and motion blur.
Put another way, even if your subject is in focus it doesn't necessarily follow that it'll be sharp. How so? Sometimes (admittedly rarely these days) it can simply be that you've pushed your lens too far. Wide apertures and long zooms can result in soft images even when they're technically in focus. If you're in any doubt, make some test shots on a static subject.
But the other biggest factor in not-quite-sharp images is technique. And by that I mean the whole shebang, from how you hold the camera to the way that you follow the action in the viewfinder... and, of course, the shutter speed that you select. Get those right, brush up on your focus technique and you should see a higher percentage of sharp shots.