Using High Speed Strobes

The Shutter-Beam interfaces with any set of studio or camera mounted strobe units via an standard PC jack output. When triggered the Shutter-Beam can directly fire your strobes hooked up to this output.

        Benefits:

        - Strobes have negligible propagation delay. .
          
(< 1/1,000,000 second, thats less than one Millionth of a second)
        - Strobes can have much faster effective shutter speed

THE TRICK:   

Camera is placed in a darkened studio with the shutter held open on BULB. When the Shutter-Beam detects the subject it fires the strobes directly. The cameras film is exposed by the flash and then the shutter is closed and film advanced for the next shot.

 

Illustration of strobe hooked up to a Shutter-Beam


Strobes as a Shutter:

When in a darkened studio your strobe becomes the shutter. Strobes can be fired at a much faster shutter speed than your cameras shutter.  High Speed strobes can achieve speeds as short as 1 millionth of a second (1/1,000,000 s) or better.

VERY EXPENSIVE!!

The average every day camera mounted and studio strobes are not as fast as a millionth of a second. But they can achieve satisfactory results. Turning the power down on these strobes shortens the flash duration. The rule of thumb is the lower the power the faster the strobe flash. Consult your flash manufacturer for exact numbers. My SB-24 at 1/16 power puts out about a 1/12,000 of a second flash. Turning the power down reduces the flashes output. Multiple flash units will help get more light on the subject.

Tricking your flash unit for faster flash:

To achieve even faster strobe outputs you can fool your flash unit into thinking there is plenty of light and use it's automatic features to turn the flash off even quicker. To do this you set your flash on automatic and take a piece of white paper and fold a portion of the flashes output directly back into its sensor. I have been told, that you can use a small piece of fiber optic cable to do the same thing, although I personally have not tried it. On the SB-24 this can produce a flash somewhere around 1/40,000 of a second or better.

  Aesthetic preference:

The faster shutter speeds, freeze more of the action. This is purely an aesthetic preference. Some people like the image to be frozen in space, others like a little movement (blur) in the picture. Frozen pictures tend to look fake, a little blur adds some realism to the shot. Again, this is an individual thing and you have to play with what you got and find out if it gives you satisfactory results for your tastes.

Strobes have no propagation delay:

The second reason to do this type of photography is that strobes have little to no propagation delay. They do not have mechanical things to move like a shutter and their reaction times are typical less than a millionth of a second.

 

 

Examples:

 

A bullet traveling at 1,200 feet/second:

 

Shutter-Beam propagation delay (1/1,000,000 second)
Bullet Moves: 0.01 inches

Strobes propagation delay (1/1,000,000 second)
Bullet Moves: 0.01 inches

You focus your camera downrange:
A total of: 0.02 inches

 

If using an 8008 camera:

Shutter-Beam propagation delay (1/1,000,000 second)
Bullet Moves: 0.0012 feet

Cameras shutter propagation delay 85mS:
Bullet Moves: 102 feet

You focus your camera downrange:
A total of: 102.0012 feet

 

FORGET the Shutter-Beam's delay

Image Blur:

The same bullet traveling 1,200 ft/s will be moving while the shutter is open or even while the strobe is flashing. This will be recorded on the film as image blur.

 

Camera at 1/1000 second shutter speed:
Image Blur: 14.4 inches

Camera at 1/8000 second shutter speed:
Image Blur: 1.8 inches

Strobe at 1/40,000 second flash duration:
Image Blur: 0.36 inches

Strobe at 1/1,000,000 second flash duration:
Image Blur: 0.01 inches


When dealing with ballistics you can see how critical both the reaction time of your equipment and the effective shutter speed is. A 22 bullet is one of the faster ballistic subjects around and it is about 1/4 inch wide. To have it travel 14.4 inches across your picture while the shutter is open will not return desirable results. You have to use strobes to freeze this kind of action. And the faster the strobes the better.

 

Questions about using strobes? Email me.


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