Issue 9: Digital Black and White

This issue is dedicated to digital techniques, but I feel it’s important to have a discussion on the differences and similarities between black and white film and digital photography. I do this for two reasons—the first is that I figure some of you may have made the transition from film to digital and have carried over some assumptions about how things work. The second is that even if you have never shot film you have probably been exposed to information passed on from film photographers about how things work. Either way, there are a number of matters at the heart of black and white photography that have changed, or at least should be looked at in a new light.

First and foremost is shedding any ideas about density. Density on film results from the metallic buildup of silver as a result of exposure and development; the brighter the light (the more energy of exposure), the greater the density on the negative (the darker the area on the film). Density determines tonality and, when compared with other areas on the negative, contrast. When you print a film negative the darker areas print lighter and the “thinner” (lighter) areas print darker. A digital image has no density, obviously, because it is virtual. The light and dark areas are results of codes being translated by the computer onto a monitor. These codes are incredibly malleable and allow for changes unheard of in silver photography that go way beyond what density, which is in essence, after development, is baked into the film, could afford.

#1 All Photos © 2010, George Schaub, All Rights Reserved

If we were to have a black and white negative of this shot (#1) we might expect it to look like this (#2). The density of the negative would be the opposite of the final positive, with more density in brighter areas and lighter in darker areas. In truth this is a digital file with the “negative” created using an Inverse command. Gross enlargement of a very small portion of the image (#3) reveals what’s really under the hood—millions of pixels all with distinct “addresses” that define the grayscale values.

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Larger format film was attractive because it required less magnification to make large prints and, when used with contact printing techniques, yielded incredible detail and tone. Photographing through a large viewfinder or ground glass was a wonderful way to immerse yourself in the image in the field. The “large format” effect today is obtained through larger sensors with high resolution (megapixel count) and relatively larger pixel (photo sites) sizes.

This CMOS sensor (#4) from a “full frame” camera yields image information and images that approach what one might have obtained in the past from a medium format camera using 6x4.5cm film.

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There are, as of this writing four general classes of sensors in digital cameras, aside from the smallest found in camera phones and digicams. In overall area size order there’s the so called Four/Thirds, the APS-C (or DX) sensor, the FX (or roughly equivalent to 35mm frame size) sensor and the so-called “large format” sensor, roughly equivalent to a 6x4.5cm or 6x6cm film frame, often found as a back modified to fit onto a 4x5 or medium format camera. Depending on how large you plan to make prints and given all other things are equal (a very rare situation), all four types of sensors are capable of producing image quality equivalent to a well-exposed and processed 35mm black and white film; the FX sensor can yield results equivalent to medium format film; and the “large format” sensors yield results equivalent to large format film.

One thing that has really changed is that there is no more black and white! Every digital image you make in a digital camera is a color—RGB—image. The vast majority of digital cameras have a checkerboard red, green and blue filter between the lens and the sensor, through which light is “sorted” and then reintegrated later in the image processor to create a color image.

When you dissect an image you find it is composed of three “channels” of color information, R (red), G (green) and B (blue). If you look at the distinct channels you can see how each works as a sandwich which combined creates a full color image (#5), but when isolated and looked at as monochrome channels shows the filtering effects on monochrome “conversion,” or rendition. Note the speedometer and gas tank and how the yellow and red colors change in grayscale when inspected on the blue (#6), green (#7) and red (#8) channels.

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