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Automotive Lighting 4: Shadows and light spill


John Jovic

Lighting a car with any artificial lights is bound to create shadows, light spill or both. Various lighting setups can be used to minimise these problems so that the out-of-camera image is as flawless as possible and so that any post to fix them is minimised, if needed at all.

Controlling Shadows from Strobes

Shadows are often cast by flashes and sometimes they can be so prominent that they can detract from an image. The shadows cast under a car are rarely of concern whilst those cast on nearby backgrounds may need attention if they are too distracting. There are several ways to reduce or eliminate shadows and one of the easiest is to avoid placing the car too close to any background or wall in the first place but this is not always practical.

Shadows in the background and light spill in the foreground need attention, as does the bright reflection in the rear wheel which could probably have been avoided by moving the flash just a few inches.    
Flashes mounted at ground level will project shadows above the car which will make them more prominent.  

A cars proximity to the background will always be a major factor in the need to control shadows. If a car is far enough from a background then shadows won't be a problem at all.

Another approach may be to light the car in such a way that any shadows are hidden behind and below the car instead of being cast above it where they are prominent. Flashes mounted high on stands would tend to cast shadows below the level of the car where they probably won't be seen, depending on the position of the camera. Flashes mounted at ground level will project shadows above the car which will make them more prominent. Underexposing the background will always highlight or accentuate any shadows, making them more prominent. If shadows are of great concern then you can shoot the background separately, either with no flash, with much weaker flash than ambient, or possibly lit separately, and then composite that with the image of the car.

If shooting at night, or in a dark environment, then you can light paint the car by walking around it as you pop the flash many times at a lower power setting (instead of using stationary flashes at a higher power setting) then you don't create a shadow at all. However this may create a completely different problem where you have lots of flash reflections in the panels which then need to be removed in Photoshop. Or, if done in daylight, a series of exposures may be shot with various parts of the car lit by separate flash exposures which are later composited into a single image. This is a time consuming option, and not recommended, but none the less an option. There are other ways to light paint, with continuous light, which create a continuous light reflection (or specular highlight) in the panels and no shadows at all. In any case light painting with a continuous light source is only practical when it's dark enough for a long exposure and when there are no nearby light sources, from light poles or buildings, to cast their own shadows so is not always a practical method.

This image is a good example of how light spill and shadows can be reduced or eliminated altogether using light painting even when the car is very close to a background. There are no shadows at all, even 'though the car was entirely lit artificially.  

This interior was lit using the light painting technique with a hand held strobe set to 'stroboscope' mode so that it would flash multiple times whilst the unit was moved around the car. When strobes are used this way they are set to a much lower power so that multiple weak flashes light the car without leaving shadows.

Controlling Light Spill from Strobes

Light spill from flashes, ie unwanted illumination, can be distracting and may need to be considered. Light spill is a common problem when the flash is used close to the ground while light spill tends to be minimal from flashes raised on light stands, unless the flashes are quite close to the car being photographed.

Assuming that the strobe can not be repositioned then the easiest way to eliminate any spill is to use a cutter such, as a piece of black card board, to shade the the part of the frame affected by light spill. Unfortunately most portable flashes don't have barn doors so it's a good idea to have a couple of small cutters on hand, possibly with a couple of magic arms, or similar, to hold them.

Another way to reduce light spill is to keep the strobes as far from the car as possible but the strobes simply may not be powerful enough in the first place and may have to be close to the car to have the desired effect. Using strobes at a greater distance requires more powerful strobes or they will have to be used at a higher power setting which will reduce battery life.

The flash sitting on the ground creates much more spill than the flash mounted on the light stand. It would be reasonably easy to place a small cutter in front of the flash to eliminate the spill on the ground altogether.  

The light spill from this strobe is quite significant although it may not even be visible in the resulting image depending on how the image is framed. If shot from a low angle then the chances of seeing the spill are reduced further.

Regardless of the lighting setup used, light spill from strobes becomes more prominent when the strobes lighting is significantly more powerful than the ambient light. This is often the case at night or when overpowering ambient light for effect. In such cases the excess light spill can potentially be used for effect, by controlling and shaping it so it is not objectionable or so that it highlights the car in a 'God Light' halo of light. Excess light spill can also simply be minimised or eliminated altogether in post by cloning, dodging or burning the area immediately around the car that is affected.

Some times light spill becomes quite obvious when the strobes are significantly more powerful than the ambient lighting, such as when underexposing the background or ambient light. In this example the strobes where mounted quite high on light stands but the strobes have a fairly harsh or distinct edge which is quite visible above. This effect may be considered undesirable by some but it can also be an advantage depending on ones taste as it does draw attention to the subject.  

The light spill is often quick and easy to remove in post if deemed undesirable. The Dodge and Burn Tools in Photoshop can be used to lighten or darken the spill and surrounding area as needed.

Using soft light sources, soft boxes or brollies, is some times more trouble than it's worth because the reflections these can create in the car are often less attractive than the shadow behind the car! They can still be a good option however and are particularly useful for interior, engine and detail shots.

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