Wednesday, April 24, 2013

Backlighting for portraits

Backlighting is undoubtedly my favorite form of lighting for portraiture. It is soft, flattering, and forgiving.When used properly, it lends a light and delicate feeling that enhances the model by down-playing blemishes and wrinkles, and eliminating unflattering shadows. The only trick to using backlighting correctly is in having proper fill to compensate for the severe exposure differential between the model's face and the background light.

Backlighting can be supplied by window light, a tungsten of flash light source placed behind the model, or with a bright sun situated behind the model instead of in front. In fact, on bright sunny days I often prefer to turn the model away from the sun and use a strong fill to compensate for the lighting differential.

This photo is back lit by soft window light, which you can see in the background. I placed two large reflectors in the foreground to kick light back onto the model and even out the exposure. The soft, delicate backlighting is very bright and airy and enhances the subject matter of mother-baby.
The only tricks to backlighting are to make sure you have proper fill, and are properly exposed. Most cameras set to automatic exposure will try to underexpose the scene. You may need to switch to manual and take a spot reading directly from the model to achieve the correct exposure. Of course, with digital cameras you can readily see what you are doing on the viewing screen.  You want a light that is balanced enough to keep the subject bright but also to have enough fill to bring in some detail in the background.

Autofocus is often an issue in backlighting because the scene is usually very low in contrast with potential for flare, both of which hamper the ability of an autofocus system to grab onto a contrasty area it can use for focus. In situations like this, the camera might hunt for focus, meaning it will rack in and out incessantly while searching for an area of sufficient contrast. A good camera and a lens with a large aperture will help.  I use Nikon pro cameras such as the D4, D800, or D600, all of which have exceptional autofocus abilities.  On top of that, for portraits I usually use an 85mm f/1.4 or 105mm f/2.8 lens where the large aperture provides extra contrast in the focus areas.

This scene is lit with a single tungsten lamp placed behind the model. That along with the plain white dress she is wearing make for a very difficult auto focus scene.
I usually use at least two, very large 4' x 6' collapsible reflectors for fill, such as these by Lasotlite. The reflectors have a white side and a side that is a mix of shiny silver and gold. It is important to have this silver/gold mix to achieve a neutral color balance from the reflector. A square rather than oval shaped reflector provides more illumination.When used in their vertical position, such reflectors provide even illumination from head to toe. While it is important to place a reflector to bounce up some sunlight to fill shadows, it is equally important to guard against using too small a reflector placed too low as this will result in a false glare to the light.

I place one reflector on each side of the model and as close as I can go together without having them enter the shot.

In this severely backlit situation there is enough reflector fill to light the model's face and maintain detail in the sheer curtains. A weaker fill or no fill would have resulted in loosing the sheer curtains entirely.  You can look into the model's eyes to see the position of the two reflectors I used, one on each side of the model.
Proper handling of backlighting is all about balance, achieving sufficient fill to evenly light the subject while also allowing some of the background to come in to provide a soft sense of place.
In all the examples provided here, it is obvious that backlighting provides a very soft, even, bright flattering light. Having a good digital camera with extensive dynamic range will make the job even easier to handle.

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