Lighting for Digital by Claude Jodoin
Part II: Metering/Reflector Fill

First and foremost I must stress that for those of you who have purchased a pro SLR camera like a Canon 10D, Fuji S2, or Nikon D100, your days of overexposing are over. Kiss them goodbye. You must either be right on with your exposures, or if you make an error, let it be only slightly underexposed (survivable). Otherwise you will be giving refunds or end up being sued. Overexposure is death with digital capture.

In this article we will be discussing lighting, light ratios, complete control of fill light indoors and out and proper digital metering techniques. For digital capture, traditional exposure methods need to be reversed 180 degrees. Meters and exposure methods are highlight based, not shadow based. Feel free to read the previous sentence several times. All digital photographers need to own and use a good digital incident flash/ambient meter and a Wallace ExpoDisc for custom gray balance. No excuses.

That being said, regardless of what type of work a photographer produces, he or she must control all parts of the subject luminance (also known as brightness or reflectance) to fit within the “printable” range of the final product, which for a normal color print, is about seven stops (five stops with detail). With the advent of Adobe Photoshop on most computers, this should be a simple task for any studio photographer to assess their own exposures. Read the RGB numbers. They will tell you whether you are “nailing” your exposures or not. Basically, a detailed white (for all printers) is around 235 (RGB). Detailed black is around 15–35 (RGB), depending on the printer and paper used. This is where testing will reveal the characteristics of the output device.

Lighting ratios between specular highlights diffuse values, and shadows have to be adjusted for the different intended final products. It’s a much safer bet to create lighting with a lower ratio (lower contrast). Contrast can be increased at anytime in Photoshop more easily than it can be reduced. Also, with the possible exception of the new Fuji S3, the small CCD and CMOS sensors in most digital SLR cameras simply cannot handle highlight overload like medium-format negative film did.

Indoor studio lighting can be precisely controlled because it is usually contained in a low ambient light environment. This allows photographers to clearly see, on the subject, the effects of different light placement at various power settings by way of the modeling lights.

Reflector fill, in the studio, when applied to the shadow side of the face only, will automatically maintain a constant ratio as the main light power varies. Reflector fill will not significantly affect the camera exposure determined by metering toward the main light. In other words, it does not affect exposure on the highlight side of the face (where we place the dome of the meter) since it only supplies softer, less intense light only to the shadow side of the subject. Reflector fill works well for studio flash, window light, and outdoors. (This metering technique is different from metering for studio flash main/flash fill requires that the dome of the meter “sees” both lights as covered in the prior article—“Lighting for Digital in the Studio” in Rangefinder’s November 2003 issue.) Unless a studio has white walls (very efficient) close enough to the subject, acting as constant reflector fill, we will need to use some sort of fill flat on every shot if the results are to be printable.

Using reflector fill, we determine exposure by pointing the incident meter’s dome at the main light. With a meter calibrated to match the digital camera, we guarantee we will never overexpose the shot. If we expose at that reading, we would have proper diffuse value exposure to easily make a print. Now if, at this setting, the shadows are too dark, you need to add fill reflector(s). The simplest, most error-free method of curing the above problem would be to have a large white reflector fill flat (9x9-foot seamless paper would qualify) on the shadow side of the subject (opposite the main light and parallel to lens axis). This would bounce soft light into the shadows and bring up detail in the file (and subsequent print). With this method, it’s almost impossible to overfill the shadows with too low of a ratio. Since white reflectors are slightly less efficient (a few tenths of a stop) and much less specular (more diffused) than silver, they provide smoother results, and their exact placement is less critical. I use a 9x9-foot white flat on casters in my studio, which allows for “worry-free” shadow fill, even for several people in a shot.

Here’s a quick metering method to measure the magnitude of the effect of a reflector fill flat and to guarantee consistent, repeatable results on future setups (provided we take notes, of course). Shield the incident dome on the meter from the main light with one hand and point that dome at the reflector flat only (away from the main light). Fire the flash and read the light bouncing from the reflector only. If a photographer were to use this method with any main light source, a precise and repeatable meter reading would result for the “bounced” reflector fill illumination only without influence from the main light at all. The dome of the meter only sees what we want it to see. Generally, this reading could be anywhere from 1⁄2 to 3 stops less than the main light reading and can be controlled by moving the reflector closer to or further from the subject. How much fill was needed would depend on the size and position of the main light source, the size and position of the fill flat, and the photographer’s tastes in what is “proper shadow detail.” I much prefer this “minus f-stops” description method for fill lighting to traditional “light ratio” methods. This “minus so many f-stops” method relates directly to the camera setting (for the main light). For example, let’s assume the photographer is short-lighting the subject from camera left. That means when standing behind the subject, placing the meter near the subject’s right cheek, and pointing the incident dome at the main light, the meter reads f/8. This is the camera setting. The photographer can then shield the dome from the main light with the one hand, rest the meter near the subject’s left cheek (the shadow side) and read anywhere from f/2.8 (minus 3 stops) to f/5.6.5 (minus 0.5 stops) for shadow fill. Just remember that the stronger shadow fill (minus 0.5) might have an effect on the overall exposure by a few tenths of a stop, meaning that the fill flat would be very close at that point, so double check by pointing the dome at the camera. Then it reads the main and reflector together. Always use the brightest reading to set the camera aperture, whichever reading it may be (dome pointed at the main or camera).

I will translate to the readings of a modern digital meter with a direct f-stop display. This assumes a main light reading and camera setting of f/8. Your readings will likely fall in between these, which is fine.

For a 1.5:1 ratio (pretty flat), meter the reflector at –0.5 f-stop from camera/main light setting, or f/5.6.5. For a 2:1 ratio, meter at –1.0 f-stop or f/5.6.0. For a 3:1 ratio, it’s –1.5 f-stops or f/4.5. For a 4:1 ratio, it’s –2.0 f-stops or f/4.0. For a 5:1, it’s –2.3 or f/2.8.7. For an 8:1, it’s –3.0 f-stops or f/2.8.0. Very few images are made with a ratio deeper than 8:1.

With the advent of large softbox main lights, sometimes you don’t need any fill reflector at all if the light source is very large, relative to the size of the subject. The shadow side ends up still “seeing” a pretty good fractional area of the large main, and thus, in effect, acts as its own fill. This type of main light requires very little fill illumination if at all. As a general rule, I prefer a “minus one” fill, which provides a 2:1 illuminance ratio (known as 1:2 with the Dean Collins methods). Where the shadow value is half the intensity of the diffuse value, or one stop less. It’s easy to darken later in Photoshop, but seldom required. Most clients don’t like dark shadows on their loved ones.

These numbers only apply to reflector fill. A different set of numbers for flash fill were already provided in my previous “Lighting for Digital” article in the November 2003 issue of Rangefinder. (See archives on the web site at www.rangefindermag.com.)

Claude Jodoin has been involved in digital imaging since 1986 and has not used film since 1999. Email claudej1@aol.com.