I thought I'd write a short piece about taking photographs of polo. Some of the tips can be transferred across to other types of sports action photography, so take from it what you will and I hope it helps you both understand the limits of what you can expect to achieve and perhaps get a flavour of how difficult it can be to get a good action shot that is also technically pleasing (the focus, exposure and composition are all satisfactory).
A polo field is around 300 yards long (about 275 meters) and therein lies the first problem, it's huge! You will spend most of your time wondering if the action will ever come towards you so that you can attempt to take some photographs, most of the time, it won't, but when it does you must be ready.
The longer the focal length of your lens then the larger arc of cover you can get, and therefore the percentage of times that the riders are in range will increase. However, there are drawbacks with using lenses of say 500mm focal length or more. Unless you are spending the kind of money that will buy you a nearly new car the lens will introduce its own issues, here are a few:
It may not offer very good sharpness at the widest aperture.
The widest aperture may only start at F5.6
The centre of the lens might be sharp but the middle and outer edges my not offer such good resolution.
If you have to increase your iso to enable a fast shutter speed then you will introduce noise/grain and some image deterioration.
A budget long telephoto lens (perhaps £1200 or more) may work best at around F8, a good few stops of light are therefore lost compared to ultra expensive F2.8/F4 lenses and they need to be recovered using a higher 'iso' or 'electronic gain'. To put things in perspective a very good sports lens of 500mm or 600mm may cost around £10,000 - I have my eye on a 300mm F2.0, but that would set me back over £5000.
To overcome the limits of range, if you want technically superior images, will cost a lot of money and there's no point putting an awesome lens on a budget camera body - the camera itself needs to have great computing power to ensure that continuous focus tracking is on par, and that the camera's memory buffer doesn't fill too quickly (higher frames per second are better). Don't forget that you must research what kind of memory card your camera will accept and buy a very high quality card with very fast read/write speeds (beware of fake cards - buy from a reputable source).
I have to compromise and I shoot with a relatively short focal length of 200mm on an F2.8 lens, so for 90% of the time I'm not taking images and when I do most of them will not be used simply because you can't predict how horses and riders will react during the flow of a match. You will end up with many images that do not have good composition, a horse’s head or backside may block the action, a rider’s face may be turned away or with multiple horses you end up with lots of legs pointing in different directions and the whole thing can just look awkward (the dynamic look of the horse is very important).
I guess just getting a suitable image takes patience and anticipation of the likely action (experience at shooting polo). I've covered some points regarding your telephoto lens and remember you'll need a good camera too, but what about other factors...
Well you can crop the image to help artificially increase the size of your subject, or chop off that unwanted horse’s backside, but don't overdo it! If you crop too much you are throwing away your image size and image quality - you may not be able to get a large print if you crop too much. I often need to crop my images (it's inevitable), but I have a limit and must consider the remaining image size. In short, if I need to crop too much then the image will not be used.
Let’s look briefly at camera settings, you'll need a fast shutter speed (around 1/1000sec or more) and will be better off setting continuous focus tracking and continuous shooting mode on your camera. Don't get carried away or you'll end up with thousands of useless images. Anticipate and start shooting a fraction of a second before you think you need to. Many images may not be perfectly in focus and that's down to how you camera/lens combination are able to cope, but you should see a percentage of useable results. That is how it starts, getting those first few shots will set your benchmark and give you that first experience of what worked well and perhaps why it did.
There's no substitute for experience - lets face it - that's often why you might consider going to a professional photographer in the first place. Whilst you are wondering about what you should do an experienced photographer will have already assessed the light of the day, where's best to stand and adjusted the camera for the best exposure metering, iso, aperture/speed etc. No doubt he/she's already rattled off a couple of test shots and is hoping for the last elements to be in place, the few things he/she can't control, a good flowing fast match (for better action shots), good light and a healthy dose of 'lady luck'.
There's always an element of luck involved, 4 or more photographers scattered around a polo field and only one of them might get that OMG image - it may not be because that person was the best photographer, it may just be that on that day the flow of the match and lady luck were all in his or her favour.
I hope this helps you understand just a little more about taking a polo image, I could go on but having some appreciation should help you realise that if you do get a great shot then you have done well. They don't come easy; although spending nearly £20,000 will certainly help (camera, lens and other suitable kit) it's not something that most are willing to do. The shots I get are achieved with kit that was worth under £3000 when new, so you don't have to break the bank, you just need to learn and be patient - most of the time you'll be stood twiddling your thumbs and remember, if you set high standards, then most of your shots may not be suitable...