Sports and Motion

One moment I was standing there shooting pictures, and the next I was getting violently jerked backwards by my shirt.  Now under most circumstances, I would turn around and confront the assailant, and perhaps, engage in an animated discussion with some rather strong words.  Because, there's nothing worse than having your eye up to the viewfinder, and being blindsided.  It's disconcerting, to say the least.  This time, instead, I turned around and thanked the guy from the Ferrari Formula One team for saving me from being run over by about 800 horsepower of racing car.  Now, truth be told, he was probably more concerned about his 20 million dollar car, than me, but regardless of his motivation, I didn't want to become a hood ornament.

That's part of what makes shooting sports interesting, not the almost getting run-over part, more the; you never know what's going to happen next bit.  Sports action, is by necessity, fast paced.  And, unless you're a judge in figure skating, you never know the results until it's over. Anything can, and usually does, happen.

One of the essential skills in shooting any fast paced subject, is the ability to freeze motion.

More after the jump...
Sure, sometimes we like to shoot pans or blurs to convey a sense of motion, and to create an interesting photo, but, it's hard to beat a razor sharp picture shot at the peak of action.  When I'm shooting with available light, whether it's artificial, or natural, the technique is fairly straight-forward.  Adjust the ISO until you can shoot with the shutter-speed necessary to freeze the action.  Ideally 1/800th of a second or faster, at the largest aperture, and the longest lens possible.  The fast shutter speed will freeze the action, and both the large aperture , which will create a shallow depth of field, and the long lens will eliminate distracting elements from the background and isolate the subject.  While I can shoot sports with any lens, when I'm trying to shoot peak action, my lens of choice is most often my Nikon 200-400mm F4.

Increasingly, these days, I'm shooting sports action with strobes.  This requires a different set of techniques and equipment.  As I mentioned, when I shoot with available light, a fast shutter-speed freezes the action, but when I use strobes, another factor plays a role too.  Shooting with strobes creates some interesting problems.  Generally, when I shoot a portrait with strobes I can rely on the flash to freeze my subject, even when shooting at a slower shutter-speed. Depending on the situation, I can sometimes hand hold my camera and shoot a portrait at 1/2 or 1/4 of a second and get an acceptably sharp picture.  There are many factors that can effect the results and I'll leave those for another post.

While shooting a portrait at 1/250th of a second, or slower, can produce great results, it won't work for a fast moving subject.  There are a couple of ways that I can freeze motion, the first of which I will talk about today.  This requires two things from the strobes.  First, enough power to completely overpower the available light, by at least three stops, preferably more.  By eliminating the role of the available light completely, this allows the flash to freeze the subject, and not have any blur after the flash has fired, and the shutter is still open and accumulating light.  

The simplest way to determine what exposure will eliminate the available light is to meter the scene normally and then start closing down the aperture with each test shot until the scene goes black.  If this occurs at 1/250th @ F5.6, 100 ISO, that then becomes the working exposure.  Now adjust the output of the strobes to achieve the correct exposure.

An example of using short flash duration during a shooting Session with Vanarts

The result will be one where the only areas of the scene that are lit, are those which the strobes are lighting.  Everything else will be black.  This can be a problem, if I want to include some of the environment of the scene, since I will then have to light that too.  It works very well if I'm trying to eliminate a cluttered or ugly background, since it will disappear.  How much work, and lighting, I have to do depends on what kind of picture I want to make, and what the environment looks like.

Lighting the subject, and the scene, entirely with strobes.

This brings up the second part of the equation.  Even though I have stopped the available light from allowing any motion in my picture, the flash can still be a problem.  Or at least, the flash duration can permit motion in a very fast moving subject.  Flash duration idAs I said, when shooting a portrait, the flash always creates sharpness, since the instantaneous burst of light freezes the relatively motionless subject.  In relation to a still subject, a flash duration of even 1/350th of a second is more than sufficient to create a sharp photo.  However, if the subject is an athlete in full motion, 1/350th is much too slow to achieve the sharpness required.

This is when a short flash duration is required to stop the action.  Essentially, when there is no other light in a scene, other than the strobe, the flash duration replaces shutter speed, in it's ability to freeze motion.  Most studio strobes, except some monoheads, have a shorter flash duration as the power output of the unit is turned down.  That is to say, a power pack has a significantly shorter flash duration at minimum power, compared to full power.  Example; a Profoto Acute2-2400 has a flash duration of 1/320th second at 2400 watt-seconds and only 1/1800th second at 300 watt-seconds.   1/320th is nowhere near fast enough to freeze action, whereas 1/1800th has great stopping power.

Note the movement in the gymnast's left foot, not quite frozen. Another from  my Vanarts class

There are other ways to use strobe and freeze action such as; speedlights and high-speed synch, or the new Pocket Wizards and their version of high speed synch.  But, I'll have to talk about that in another post, because all this talk about flash duration and synch speeds is starting to hurt my head.