A Time MachineThursday, April 14, 2011
These days camera manufacturers boast about fantastically fast shutter speeds. They harp about freezing the quickest motion.
|Mission drag race circa 1979|
When I purchased my Pentacon-F in 1958 it boasted a focal plane shutter that had the then very fast 1/1000 second shutter speed. Since the advent of photography in the 19th century there have been only three principal kinds of shutters. The first one involved the simplicity of counting the seconds and (even the minutes) and then placing a cap over the lens. In those early days exposures were measured in minutes.
The first practical shutters involved the mimicking of our eyes in which little blades opened or closed to allow light. These shutters were complex and had to be positioned between the glass elements of a lens. They were called between the lens shutters or by their brand names. The German ones were called Compur or Prontor and the Japanese versions were Copals. Because of their complexity these shutters were never any faster than 1/500 second.
There was another shutter that could be designed to give faster shutter speeds. These were called focal plane shutters because they were positioned right next to the film (and in modern digital cameras to the sensor). These shutters were made of cloth (the later ones in the beginning of the 70s were made of thin metal and the better ones of titanium). Cloth shutters consisted of two rolls or curtains that traveled from left to right or right to left (depending on the manufacturer) and the speed of the shutter was a combination of two factors, the actual speed of the rolls of cloth and the width of a slit that was between curtain A and curtain B. The narrower the slit, the faster the shutter.
|Horizontal moving focal plane shutter|
Modern metal shutters are designed to go from up to down as opposed to left to right or right to left. Because the slit travels a shorter distance (the width of the film or sensor and not the length of the film or sensor), they can achieve faster speeds like 1/4000 second.
But a few reading this might understand that freezing motion does not necessarily show motion. Sports photographers have known for years that in such games as baseball, when a batter hits the ball, the motion of his body hits a peak and paradoxically motion is zero. The same applies to a basketball player about to dunk the ball. At these times a shutter speed can be a slow one and yet capture the “motion”.
Another technique of sports photographers is one called panning in which the camera is moved (smoothly) in the same direction of the motion. Thus if you follow a runner (the shutter speed also depends on how close you are and or the focal length of the camera lens) at about 1/15 of a second the relative speed of the runner and your camera is zero while the speed of your camera in relation to everything else (be it the background or foreground) is the speed of the runner and of your panning. This results in that background is blurred while your runner can be sharp. The illusion of motion (the blurred background) tops the idea of using a fast shutter speed which show your runner stopped in motion and everything is sharp (runner and background).
|My Pentacon's horizontal traveling cloth focal plane shutter|
In 1964 when I shot the Mexican Grand Prix I knew a bit about panning and had to experiment. The formula that I figured out (after many mistakes) was the use of a shutter speed that was close to the speed of the car in kms per hour. This meant that the picture here of Dan Gurney in his Lotus with a Coventry Climax engine was panned at 1/200 of a second. My Pentacon F had that shutter speed (and 1/50, 1/100). Later cameras shelved that speed and shifted to 1/60, 1/125, 1/250 and so on.
|Curtain A & curtain B and where the slit would be.|
One who knew all about this many years before was French photographer Jacques-Henri Lartigue who photographed the 1912 Grand Prix of the Automobile Club of France.
His camera of choice was a bulky Ica Reflex that used a 3½/x4¾ inch glass plate. The camera had a Zeiss Tessar 1:4.5 150mm lens. The peculiarity of this camera with a top-mounted focusing screen was its horizontal focal plane shutter. One of the problems that Lartigue had was that the image in his viewfinder was reversed. Left was right and right was left. When he panned his camera in the same direction as the car he had to fight his internal instincts to go in the opposite direction.
|The titanium downward traveling shutter of my Nikon FM-2|
Why are the wheels not round? The answer is simple but interesting. The slit of the focal plane shutter (between curtain A and curtain B was going opposite to the direction of the car. As the wheels moved in opposite direction to the shutter the shutter caught the wheels where they weren’t (and had been!). I cannot make this any simpler so here you will simply have to take this on faith!
When the between the lens shutter (be it a compur or copal or whatever) opens from a closed position and then closes to expose the light on to the film or sensor, every part of the picture is exposed at the same time.
This is not the case with a focal plane shutter. All images that lie on film or a sensor are upside down. Modern cameras have a viewer that shows the image right side up and left being left and right being right. That is why expensive DSLRs have that hump. It is a pentaprism that does all the corrective shifting.
|Dan Guerney Lotus Coventy Climax 1964|
With that image being upside down, let’s imagine that you are taking a picture of your Uncle Billy. His head is down and his feet are up. The shutter on a modern metal focal plane shutter is going down. This means that his feet are exposed first and lastly his face.
This means that in a short time consideration, Uncle Billy’s feet are exposed first and thus are older and his face is younger in elapsed time!
I have always been fascinated by this useless piece of information. Consider the ramifications of a horizontal group shot of your family. Some of your family will be increasingly older as the shutter travels from one side to the other.
|Lartigue's famous photograph|
And lastly, when I took the picture of the Mission drag racer I used my Mamiya RB Pro-S. I had the same viewfinder (but my Mamiya lens had a between the lens shutter) as Lartigue. Left was right but right was left. When I panned the picture I had no trouble. Why? It was only a couple of years later that I found out I was dyslexic! Was Lartigue also dyslexic?