18 Dec 2009

Project: Photographing movement.

Exercise: Panning with different shutter speeds.

The final section of the Introduction to The Art of Photography involves another exercise in photographing movement.  In this exercise the object is to pan the camera to follow a moving subject in order to keep the subject sharp and allow the background to show motion blur instead.  This is the opposite of the previous exercise when I photographed moving people with a stationary camera.  The technique is essential when trying to achieve sharp photographs of very fast moving subjects like a racing car or an aircraft at a display because even with a very high shutter speed the subject will blur slightly.  Certainly, if the available light is low then even a slow moving subject may well need a panning technique because a high shutter speed may not be an option.  The technique also has the advantage of achieving a blurred background which gives the feeling of speed to what otherwise may appear to be a very static photograph.

On a technical note, I set the auto-stabilisation on this lens (23-105 1:4 L USM IS) to off as it won't function when the camera is being panned.  My Canon 100-400 1:5.6 L USM IS has two auto-stabilisation settings, one of which can be good for panning as it corrects for movement in the vertical plane but not in the horizontal plane and most panning is done in horizontally.  I also pre set the lens focus point as it is hard to achieve an accurate focus in time to capture a fast moving subject.

The first subject that I chose was a moving train but there weren't enough of them to allow me to complete the task without turning into a block of ice, the temperature being below zero!  I did, however, take a couple to show the difference between a panning shot and a stationary shot at 1/60th sec.

1/60, f14, 28mm, ISO50, Camera still

1/60, f10, 28mm, ISO50, Camera panned
 The observation from these shots is that the level of motion blur is very similar for the moving train and the background, depending on if the camera is panned or not.

So to preserve my fingers from frost bite I raided Starbucks for hot coffee and then started shooting the cars moving over the level crossing.

1/30, f22, 58mm, ISO50
At 1/30th a well panned shot can freeze sufficient of the subject to achieve a good level of sharpness.  Bear in mind, however, that 1/30 is probably the slowest speed that most photographers would attempt any hand held shot if they wanted a sharp result. The sharpness of the drivers hand in the blow up below shows that even at 1/30th it is possible to get a good result. Of note, I was panning with respect to the centre of the car, which is the area that shows no motion blur.  The front and rear of the car are still subject to motion blur as they are moving at different relative speeds when compared to the middle of the car. 

Section from photograph above
At 1/30th sec the background shows a high level of motion blur which isolates the car from it to such a degree that it isn't even obvious that the car is on a level crossing.  This can be an advantage but it also means that the subject is now out of context and must stand on its own merit.

1/60, f16, 58mm, ISO50
At 1/60th sec the cars are becoming clear and sharp whilst the background still retains a nicely blurred effect.  In my mind this was a good choice of speed for this particular subject, balancing the sharp look of the car against the blurred but recognisable background.  Of course a faster car would have needed a faster pan and therefore a faster shutter speed to achieve a good result...  nothing is cut and dried!

1/125,  f10, 58mm, ISO50
At 1/125th the car is very sharp and well defined and the background is showing much less motion blur.  Indeed, the blow-up below shows the car Mustang insignia in the centre of the turning wheel quite clearly.  Of course this has the effect of 'reducing' the speed of the car which now appears to be going much slower than the white 4x4 in the first shot above.  So the shutter speed becomes a trade off between seeing the detail on the subject and achieving a good blurred background.

Section from photograph above

Panning is an essential technique when dealing with moving subjects, particularly when the available light is limited.  It is often the only way of making the subject recognisable from a mess of blur that would otherwise have occurred.  In the same way demonstrated by the exercise in depth of field, panning can emphasise the subject and bring it out from the rest of the photograph in a way that other techniques can't.  Panning also has the effect of demonstrating the speed of the subject, bringing an illusion of motion to the fixed medium of a photograph.  As such it is an excellent tool to keep in a photographer's bag of tricks and doesn't only need to make an appearance at the F1 racing circuit.


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