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 p.1 #7 · Thoughts on portraits from the 40's | |
There is a ying/yang relationship between the contrast of the light sources used for portraits and the contrast of the recording medium. B&W film can be developed in a way that renders even high contrast lighting, like a face in direct sun with dark shaded eye sockets, in a way that looks soft and natural. Try to do the same with a digital camera with half the dynamic range and the same face with correctly exposed shadows will have no detail in the eyes.
Over the years as portraiture shifted from longer range B&W films to shorter range color emulsions and then to transparency film which has even less dynamic range than today's digital sensors photographers learned to compensate for the greater contrast of the recording medium by using less contrast with their lighting scenarios.
That explains why feathered reflectors and dishes replaced focused fresnel sources when portraiture moved to color negative film and why umbrellas, soft boxes and diffusion panels of every increasing size became the norm when most commercial photography intended for print reproduction was done on easily scannable transparency film which had shorter dynamic range than color negative emulsions.
The way to mimic the look of the 30's and 40's B&W era with today's digital equipment is to strike a similar ying/yang balance between the contrast of the sensor and the light source. The B&Ws are characterized by the distinct placement of light which is a result of using a small controlled key light source, combined with a buttery-smooth transition of tone between shadow and highlight which resulted from the ability of the film to handle high contrast and the way photographers of that era used fill.
With digital the way to handle contrast is to control the contrast range of the scene by overlapping the key light source creating the highlights over even fill. Starting in a dark room you'd first want to use the fill source to evenly light the scene until the darkest shadow detail in the scene is recorded by the sensor at whatever f/stop was chosen for DOF. Once the entire scene is lifted to the point where the sensor can record detail in the darkest shadows with only minimal noise, turning on the off axis key light will create the highlight pattern which defines the 3D shape. The areas not hit by the key light remain the same with whatever level of detail and perceptual softness that was defined at the outset with fill. Then its just a matter of positioning the key light for the desired highlight pattern and raising its intensity until white textured highlights (like a white towel held near the face) are 1/3 stop below clipping.
What controls the contrast and apparent softness will be the foundation of fill, more so than the size and distance of the key light modifier. Where some err in trying to duplicate the 30's look is by using large, very diffuse key light modifiers which don't have the directional control that the older sources did. Many of the old B&W shots have what I call for want a of a better metaphor, an "iron fist in a velvet glove" look: a rich full range of tone from dark to light combined with the smooth transitions both in the shadows and highlights. The rich range of tone is created by controlling where the light doesn't go, something that is difficult to do with some the huge modifiers used today and the ill-founded assumption by some that bigger is better.
Starting with fill from the direction of the camera ( the only position it can reach everything the camera sees and records) mimics the ability of the B&W to handle contrast by instead reducing the contrast of the scene. Direct sources such as fresnel lights, just the reflector or a reflector with a metal grid will tend to make the highlights the key light create more contrasty than the B&W era (i.e. the highlights will look "hotter" or more harshly specular because of the shorter range of the sensor records the tonal transitions in the highlights differently. The direct controlled look of the key light can perhaps be duplicated best with a small softbox with a egg-crate grid which offers the needed directional control of the key light with the ideal balance of diffusion to match the perceptual effect of the B&W era film/lighting combinations in the highlight transitions.
The difference in contrast characteristics of digital will also affect the look of natural lighting vs. what B&W negatives are able to achieve. One of the initial set-up tests for the Zone System suggested by Ansel Adams was to put a familiar face in direct sun then find the combination of actual film speed and negative development time which would render the face with a full range of detail from highlights on the forehead to shaded eye sockets in a way that fit a print made on #2 paper. Whatever film speed and development time it took to produce that result then became the baseline for "normal", with adjustments made from it for scenes with more or less contrast. Try the same thing with just ambient light with digital or color film and the result will be dark eye sockets because the recording medium can't handle the contrast. That's why its necessary to use a supplemental, non-overlapping source of fill with color film and digital to alter the scene contrast, when possible, to match what the sensor or film/print combination can record with detail. With digital learn to control the fill independently from the highlight source and you can handle the contrast and record a full range of detail. 
Chuck
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