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Rig Shots 9: Selecting the optimum shutter speed for rig shots

Author/Copyright:

John Jovic

Achieving the optimum amount of background blur is the key to making an effective rig shot, assuming of course that a suitable and interesting composition has been created. If you can get just the right amount of background blur then you will allow the viewer see the context or story of the image (assuming the composition allows for this in the first place, another major failing in most rig shots) whilst still having enough movement to make the image dramatic. If you go too far, then the entire background is nothing but blur with very little recognizable detail, no context, no story, just a car floating in a meaningless background!

There's no such thing as an optimum shutter speed for a rig shot, just an optimum amount of background blur, but this will also be subjective to a degree. The optimum amount of background blur varies with the composition and the effect you are wanting to achieve. Background blur across approximately 1/8 to 1/3 of the image is commonly quite effective. Extending the background blur well beyond those amounts can hide the background and context of the image resulting in a car kind of floating in a meaningless blur. Sometimes a 1/2 a second exposure will do the trick, other times 20 or 30 seconds is needed to get the right amount of background movement.

#1
speed: walking pace
exposure: 3 seconds
aperture: F8
filters: B+W ND 106 + Circular Polarising filter

#2
speed: walking pace
exposure: 6 seconds
aperture: F6.7
filters: B+W ND 106 + Circular Polarising filter

#3
speed: walking pace
exposure: 8 seconds
aperture: F8
filters: B+W ND 106 + Circular Polarising filter

#4
speed: walking pace
exposure: 11 seconds
aperture: F9.5
filters: B+W ND 106 + Circular Polarising filter

The above examples show the same image at various exposures. There's not much difference between the 3, 6 and 8 second exposures, possibly due to small differences in the way the car moved, but the 11 second exposures are probably too long.

Background blur is also determined by the way the car moves during the exposure, not just the shutter speed. If the car moves in a straight line then the background may not move very much within the frame, especially where the camera may be positioned to shoot a dead front/rear or a front/rear 3/4 image. If the steering wheel is turned so that the car moves in a gentle turn where the camera is on the inside of the circle then the background blur is greatly accentuated so a/ the car doesn't have to move very much and b/ a shorter shutter speed can be used to achieve significant background movement. If you turn the steering wheel so that the camera is on the outside of the turn then you may find that the background actually moves very little if the background is close to the centre of the radius of the turn. Some parts of the background may even appear stationary if they are in the centre of the turns radius. As long as the background is some distance from the centre of the turning circle it will move at an accelerated rate compared to when the car simply moving in a straight line.
 

 
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