Photographing Birds in Flight (Part 2) by David G Hemmings
Know your subject: This holds true for all nature photography but is just as important in flight shooting. Woodpeckers, such as this Red Headed Woodpecker in the image, have an arcing, swooping flight pattern much different than say, waterfowl or many raptors. Passerines often make jerky and unpredictable motions in flight as they fly about catching meals. Some birds hover for periods of time while many others do not. Many birds are migratory birds, so it is crucial to know when and where they will be at all times of the year. Learn their flight routes and the best locations for you to setup at any given location. It is also important to be as inconspicuous as possible. Always walk likely and carry a big lens is my motto. The more attention you pay to not alarming your potential subjects the better your chances will be of getting the image you desire.
Equipment: We often hear that it is not the equipment in nature photography that matters most, but rather the person operating the equipment. It could be said that bif shooting is the exception to that statement. (Note. I shoot with Canon gear, and references here are for Canon bodies and lenses, but other manufacturers have similar equipment and settings). Some camera bodies and lens combinations are simply better at acquiring and holding focus lock on your subject than other bodies and lenses. For example, your keeper rate when shooting birds in flight is likely to be higher if you are using a 1D series than say one of the 30/40/50D bodies. This is particularly true the more difficult and fast flying your intended subject is.
Which shooting and metering mode works best?
In my opinion, and it is just that, neither Av nor Tv is ideal for flight shooting, although I know photographers that use Tv with some degree of success. Shutter speed is usually more important than aperture for flight shots. For me, lighting varies too much in quality and quantity to get consistent results on days where any clouds are present with either Av or Tv. I prefer to meter for the intended subject manually using evaluative, partial or incident metering. Knowing the subject will be exposed correctly regardless of sky or other background anomalies eliminates one more variable for me and increases my chances of producing "keeper" images. Your mileage may vary, but at least try shooting in manual mode the next time out - enjoy the total control it gives you. Automatic modes and metering have their place, but flight shooting is not one of them. Think Manual Mode!
One Shot, AI Focus or AI Servo focusing mode?
First, let's take a look at the differences in these three focusing modes. With one shot, when you depress the shutter part way, focus is attained and locked - if you trip the shutter, your image will be made at that focus distance. In one shot mode, if focus cannot be attained, the focus light blinks, and the picture cannot be taken even by depressing the shutter fully. Most cameras have a significant shutter lag, and focus won't be accurate for any moving subject unless it is moving parallel to you. Intermediate cameras such as 10D, 20D have AI focus mode, which is automatically activated when shooting in one shot mode, and the subject moves. It is not as fast or accurate as AI servo. AI (Artificial Intelligence) Servo utilizes predictive AF - you depress the shutter part way, and the camera continually calculates where the subject will be, tracking the subject and focus is constantly adjusted accordingly. Auto focusing and subject tracking continues as long as the subject remains within the Area AF Ellipse. In my opinion, AI servo is much more accurate for flight shooting. There are exceptions, and some highly skilled flight shooters use AI focus successfully by constantly tapping the shutter, tweaking focus and tripping the shutter at the exact moment when the subject is sharp in the viewfinder. I shoot in AI Servo 100% of the time.
Which sensors to activate?
This of course varies with your camera, brand and its respective options and number of available sensors. I will describe Canon since that is the system I use, but other systems have similar, if not the same options. My EOS-1D Mark II has 45 available AF sensors. For general use, I activate Custom function (C.fn) 13-3 which makes the center AF point and 8 peripheral points selectable. For about 65% or two thirds of the time flight shooting, I use the center AF point only. It is just faster for me, and it's the best way to AF on a bird's eye when that opportunity presents itself, say with large birds. Occasionally, I use C.fn 17 to expand the AF activation area to either 7 or 13 AF points. This is particularly useful with small, fast moving subjects. C. fn 20 allows me to adjust AI servo sensitivity such as keeping AF from being thrown off by an object moving between myself and the subject. If I have an unobstructed background such as blue sky, I will often use all 45 sensors. The "ring of fire" is highly effective and fast to acquire AF, but it will not work well against busy or uneven backgrounds.
Focus delimiter and stop focus button:
Many modern telephoto lenses have focusing limiting capability. By using that feature, we limit the distance the lens travels searching for AF. AF itself does not work any faster, but time to acquire AF is reduced by up to 50%. Another feature present on long lenses is the focus stop button. If I press that button focus stops right then. That can be useful in low light or anytime your camera/lens locks on focus but has trouble, for whatever reason, holding focus.
Other relevant factors:
AF speed is determined by both camera and lens. AF sensor configuration, spacing and sensitivity vary among body brands and models. The same holds true for lenses - some of the fastest lenses have focusing motors built in. The amount of light reaching the sensor configuration affects its speed. That is why a 300mm F2.8 lens will acquire focus faster than a 300mm F4 lens. We all love teleconverters for the added magnification they afford us, but again it's a light level issue - teleconverters cost us from 1-3 stops, and thus affect AF speed and performance
Never stop trying!
Even after you become adept as a bird in flight shooter and fully understand and use all the technical features described above, there is still no guarantee you will get fantastic images. Having the tools is all too often not quite enough. Persistence will get you there. Many times I have spent hours and days in the field to get just 3 or 4 top notch images. Keep practicing and never give up!
David G Hemmings