Proper Exposure Matters!

Back in the fall of 1972, my very first photo school assignment for Commercial Photography 101 was entitled "An Industrial Interior." I had read Ansel Adams’ Basic Photo series the year before, and I was enthralled with his Zone System for exposure and development. So by the time I got to school, I had enough of the basics to know how to "expose for the shadows and develop for the highlights."

Fig. 1

To shoot the assignment, I drove to a local hydroelectric power station, strolled inside (you could do that in those days) and set up my brand-new Calumet 4×5 view camera (Fig. 1). Practicing the Zone System more or less requires the use of a 1° spot meter, and using one gave me the feeling of great precision in my black-and-white photography. Reading a 1° spot in the darkest shadows at the end of the turbine facing the camera, I remember placing that value on Zone II, thus determining the base exposure. Then, reading a highlight in the clerestory of the roof, I recorded a value in my notes to determine the development for Zone VIII, knowing full well that would put the overhead lights into specular (Zone X) territory. I no longer have those notes from this early effort, unfortunately, but I distinctly remember the range of the scene was great enough that it required pulling the development by several stops to bring the very bright white of the clerestory down to Zone VIII.

Fig. 2

By then I had done enough darkroom testing to know what negative densities could be produced on PLUS-X sheet film with various development times, temperatures and agitations. Despite all that, pulling this first assignment out of the soup was still a revelation. The tones were magnificent (Fig. 2).

Based upon a deceptively simple idea, the Zone System mapped 10 exposure values (basically, ƒ-stops) found on the Weston meter (Weston called them light values) to 10 evenly spaced shades of gray in a print. Using this number of tones came conveniently close to the dynamic range of many black-and-white films at the time, so the system gave photographers very direct control over how and where they represented tones from a given scene. It only required that you "previsualize" your final output—which in those days meant a print. Ranging from a tone "slightly lighter than black to a tone just perceptibly darker than the paper base," the 10 tones appeared roughly spaced like this in reproductions overseen by Adams in his own books (Fig. 3).

Fig. 3

Ansel Adams wrote: "A gray scale of 10 steps seems to be most convenient. With solid black and pure white as the extremes, there are 8 discrete shades of gray in between—not too many to visualize, and yet enough to symbolize various values in the subject."

Fig. 4

Adams also wrote: "The photographer who wishes to work toward a predetermined result must visualize the tonalities in which he wants certain important parts of the subject to be represented, and plan his exposure and subsequent treatment accordingly."

Sounds easy, doesn’t it? In Adams’ world of film, this meant understanding and controlling the relationship that real-world exposure values have with the reflective tones one hopes to achieve in a print. Adams also used various techniques in his "subsequent treatment" (read: film processing), allowing him to expand or compress the tones within that scale to complement his subject matter.

When identifying the tones that might be produced by a 10 ƒ-stop range in his Zone System, Adams came remarkably close to shades of gray as they occur in a gamma 2.2 space, using 10% increments in Lightroom’s 0 to 100% scale (Fig. 4).

Fig. 5

But don’t think for a minute that 10 exposure values in a digital capture will map to these same tones at all! To determine exactly where actual ƒ-stop increments of light would fall in the RAW world, a little testing was in order. This meant dusting off my trusty spot meter and devising a gradient that would fall across a white board, giving me as many exposure values as possible in one capture (Fig. 5).

Just as it did in the Zone System, exposure comes first in any digital test. An optimal digital exposure places a value that you want to be pure white as high as possible in your exposure range. Adams called this bright value just above Zone IX "the maximum white value of the paper surface."

For the purposes of these tests, I’m adjusting my exposure to place my starting value at the highest measurable tone (99.8% to 99.9%) in the gradient that isn’t clipping (100%). Of course, the clipping point that each RAW processor indicates will be different, but once you’ve made a commitment to a specific exposure, the rest of your tones flow from that.

Fig. 6

As an example of how radically different two RAW processors can be, let’s compare Lightroom 3’s 2010 Process Version to the new 2012 Process Version. (All tests were shot with a Canon EOS 5D Mark II.) Starting with the 2010 Process Version and using a camera exposure (1⁄3 sec. at ƒ/5.6) that puts a measured exposure value of 10 at 99.8%, the subsequent exposure values fall on these tones (Fig. 6). The first thing you probably notice is how compressed the tonal range is, especially in the shadows. The 5D Mark II is showing only about 7 stops of useful dynamic range here, and the lower shadow values are stacked up very close together.

Fig. 7

Turning to the new 2012 Process Version, we find that EV 11 with more than one full stop of exposure (1⁄2 sec. at ƒ/5.6) falls at 99.9%, which then yields these values (Fig. 7).

The difference is pretty dramatic and points to several notable improvements. First, the entire range expands out across 11 EVs, which causes the top five steps to much more closely resemble the top five values in Adams’ Zone System. The lower five steps still show less differentiation than on the Zone System scale, but these last three steps at least now have usable values.

Highlight rendering has changed considerably, with the top two stops of exposure being compressed into just 9% of your top tones—9% in Lightroom’s gamma-encoded 0 to 100 scale, which could represent as much as 75% of your total gray levels in the capture’s linear 14-bit space! Compared to the 2010 process where the top two stops of exposure account for fully 30% of your gamma-enc
oded tones, the new process produces a much more "film-like" transition into white, with many more available tones to play with.

These results convinced me of two things. First, more than ever, proper exposure is paramount with digital. Placing your maximum white value as high up in the exposure as possible ensures that you’ll have the most bits to play with and the greatest possible separation in the midtones. Second, I clearly would have to start carrying my spot meter with me everywhere as a standard part of my camera kit.

So now that you know where your tones are going to fall in Lightroom, what are you going to do with that? In my next installment of this two-part series, we’ll look at just that, with a fun analysis of how to use highlights with whites and shadows with blacks in the new 2012 Process Version.

See more of George Jardine’s photography, read his blog and check out his Adobe Lightroom tutorial videos at

Leave a Reply