Light—Science & Magic- P6

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Light—Science & Magic- P6 LIGHT—SCIENCE & MAGIC The real CCD has an additional disadvantage that film didn’t: the curve simply ends at the top. Photographers tend to routinely overexpose, whether shooting film or shooting digi- tally; although it may not be a virtue, it’s still a fact. Photographers shooting film do so because it’s “safe.” Highlight loss is easier to compensate than shadow loss. Photographers shooting digitally do so to keep as much if the image as possi- ble out of the “noisy” lower ranges. Digital photographers can- not overexpose nearly as much, however, because of the abrupt loss of detail at the top of the curve. USING EVERY RESOURCE The difficulties of white-on-white and black-on-black subjects are not caused just by the subjects themselves. The problems are related to the very basics of the photographic medium: scenes get recorded on those portions of the characteristic curve that preserve the least detail. This means that no single technique, or even group of techniques, is always adequate to deal with such subjects. White-on-white and black-on-black require complete com- mand of all types of photographic techniques. The two most essential sets of these techniques are lighting and exposure con- trol. These two work together to produce each picture. The rel- ative importance of each varies from one scene to another. We sometimes think primarily about exposure control and in other situations use lighting techniques as the primary tool. The remainder of this chapter will discuss both and suggest guide- lines about when to use which tool. WHITE-ON-WHITE White subjects on a white background can be both practical and appealing. In advertising, such subjects give designers maximum flexibility in the composition of the piece. Type can go anywhere, even over an unimportant part of the subject itself. Black type on a white background is likely to survive even poor reproduction in a newspaper. Furthermore, photog- raphers do not have to worry as much about making the crop fit the available space. If the picture is reproduced to keep the background pure white, readers cannot see in the ad where the edge of the print might have been relative to the subject. 238 THE EXTREMES Grain Some photographers still shoot film, for very good reasons. Even after technology renders film truly obsolete, there will probably still be some photographers still shooting film just to be different, like those few who still print on 19th-century emulsions. You can overexpose negative film to be safe, but we need to warn you that overexposure increases grain. The two factors that most affect grain size are the sensitivity of the film to light and the density of the image. We usually choose the slowest film that allows an acceptable aperture and shutter speed. After that, we minimize grain by paying attention to density. The denser the image is, the coarser the grain size is. It makes very little dif- ference whether a density increase is caused by an exposure increase or a devel- opment increase. The effect on the grain is similar. This means that the grain is not uniform throughout the scene. The highlight area has more grain than the shadow area because of the density difference. This fact surprises some photographers, especially those whose negatives are consis- tent enough to print with very little manipulation. The denser areas in most negatives produce light gray or white in the print. The grain is coarse in those areas, but it is too light to see. Highlight grain is also concealed in a print by further highlight compression inherent in the characteris- tic curve of the paper itself. Suppose, however, the highlight detail is not adequate with a normal printing exposure. Depending on the scene, most photographers remedy the problem by increasing either the general printing exposure or the exposure just in the prob- lem area (a “burn”). This makes some of the highlight steps print as if they were middle steps. Printing the denser gray steps as middle steps reveals the coarsest grain in the negative. Highlight compression in the negative is not as bad as shadow compression, but the defect is compounded by increased grain. The resulting effect on image quality can be even worse. For many years good photographers realized that black-and-white film, printed with modern enlargers, needed about 20% less development than the film data sheets told them, and they got much less grain with the reduced development. Photographers shooting color negative film, however, were pretty well stuck with standardized development times because reducing development hurt the color badly. Such photographers owe a lot to former president of the Professional Photographers of America, Frank Cricchio, who, before he started shooting digi- tally, worked out an exposure system for color negative film that guaranteed ade- quate exposure without overexposure. He proved his system by making much larger prints than other photographers, with better sharpness. 239 LIGHT—SCIENCE & MAGIC Raw For at least a century photographers regretted that S-shaped characteristic curve and wished the filmmakers could get it straight. They saw the loss of highlight and shadow detail in those parts of the curve and rightly th ought that detail could be improved by a linear curve. Now, with digital photogra- phy replacing film, we have our wish, but it turns out we don’t like it after all. The Raw file format off ...