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 p.2 #5 · Lighting Ratios, beyond the numbers.... | |
I didn't do a very good job of explaining it apparently but the "baseline" exposure method I'm suggesting is similar to the Zone System, modified to accommodate the inherent limitations of digital capture — short sensor range.
Baselines are a process control concept. With any engineered process there is some "nominal" result produced when all the parameters are controlled in the way the process is designed to work. With the negative/print system the nominal result was obtained when the darkest detail had a slight density on the negative and the highlight density on the negative in the brightest solid objects produced a density on the print slightly darker than the white paper base.
The magic of photography process has always been that when you do manage to expose the shadows and highlights correctly at the same time it creates a state of visual nirvana where the technical parameters and the perceptual impression mesh perfectly and EVERYTHING IN THE MIDDLE LOOKS NORMAL! Get the white shirt and black suit exposed correctly and the face will be rendered accurately regardless of its color or tone.
The Adams Zone System has three process control baselines.
1) 18% Gray Card = Zone V the middle of the tonal range perceptually: It was also the technical baseline for exposure measurement by reading the card in the same light as the scene with an averaging reflection meter. Adams had an irrational dislike for incident meters, despite the fact they produce the same result as a reading off a gray card. Metering long ago shifted to a 12-13% reflectance baseline, but the Kodak Card remains at 18% in part because Adams threw a hissy-fit when Kodak proposed changing it to the new standard, which would affect this baseline and the ZS gravy train.
2) A Sunny 16 clear day is a "normal" scene range: A clear sunny flat lit (light over shoulder) scene has a range of about 10 f/stops, part of the Zones = f/stops confusion that persists today. Since Adams did most of his photography outdoors on clear sunny days it was a logical baseline to use.
3) Development to fit the "normal" scene range to # 2 Print paper: The common practice with roll film is to develop the film for a standard baseline time. That then requires different contrast range papers to fit sunny, overcast, snowy scenes. Instead Adams preferred to print all his photos on #2 grade paper and the system is based on predicting what development time is needed to fit the scene to the #2 print at the time is captured. Thus the negatives for a normal scene and the same scene on a snowy or overcast day would have different development times to fit the scene range to the print range.
Zones are not f/stops but rather tonal definitions on both print and in the scene created by Adams. A capture was nominal when the print reproduced the zones (tones) on the print in the same way seen by eye, with the same 18 % of light reflected off the photo of the baseline gray card as in the original. If you laid the card and print together they would match. So you see the "Sears Look" is in fact similar to the Zone System baseline... 
Zone 0 - Maximum black on print. Black voids with no detail see. Film border
Zone 1 - First detail seen above black.
Zone 2 - First discernible texture.
Zone 3 - Average dark materials.
Zone 4 - Dark foliage, stone, landscape shadows and portraits in sunlight.
Zone 5 - Middle Gray 18% reflectance: north sky, gray stone, weathered wood.
Zone 6 - Average caucasian skin, shadows on snow or objects.
Zone 7 - Light gray objects, very light skin.
Zone 8 - Textured objects (i.e., white shirt / towel), highlights on caucasian skin.
Zone 9 - Smooth white objects without texture, snow in flat light.
Zone 10* - Print paper base: Specular highlights: reflections of light sources in highlights.
* In the 1968 edition of his Basic Photo Series (the one I used) Adams didn't assign a "Zone" number to the white paper base of the print.
The Zone System workflow was "calibrated" with two simple tests:
1) True film speed: When an 18% gray card was metered at the rated film speed more often than not the shadows in the same light would not be exposed correctly on the negative. The same is true for the highlights on a digital camera which is way meters must be compensated to match camera ISO. The compensation in the Zone System was done by changing the ASA speed on the meter until the grey card reading did put detail from Zone 1 in the scene (detail above inky void) on the negative and print (when exposed for border = max. black).
2) "Normal" film development time: Only one development time for the film fits a "normal" (i.e 10 stop) scene to the range of a #2 print. By coincidence the density range needed for a #2 print is 3.0 density units. Density units are log10(Incident/Transmitted) and .30 cuts light intensity by 1/2 the same as an f/stop. So the #2 print by virtue of being needing 10 x .3 = 3.0 density units on the negative was referred to as having as "10 stop range". That's also part of the "Zones = f/stop" confusion.
You would determine "normal" development time by putting a subject in direct sun with dark and light clothing and shoot four or five sheets or rolls of film identically at the ASA speed determined in the first test. Each would be developed separately for a different time, then printed with standard "baseline" methodology. The print exposure was based on making the film base (no scene exposure) black and the lightest negative density above the film base dark gray (Zone 1).
When the four test prints were laid out can compared the shadows would be identical on all of them — solid black on the border with perfect detail in the shadows. We'd file the negative carriers larger to create a black border with the negative base as a hallmark of Zone System zealotry. What changed on the prints with development time when prints were "exposed to the left" was the highlights. Under developed film has lower density which makes the print highlights darker than nominal and muddy gray similar to an underexposed digital file. Over developed film will increase negative density to the point where the print, when exposed for the shadows, will have blown highlights similar to an overexposed digital file. The development time which as "normal" made the print look "real" and every bit as good, technically as one of Adams' prints. in addition to the "normal" scene time you would do additional tests to find the times needed for 8,9, 11, and 12 stop ranges which in ZS parlance were Normal - 2 development, Normal - 1 development, etc.
The shooting workflow, before spot meters, would be to meter the 18% card for exposure then visually compare it the scene. With experience scene range outdoors could be guessed based on the conditions most of the time. When in doubt average meter reading could be taken off light and dark content in the scene to determine range precisely. The range determined what development time was needed.
By the time I learned the Zone System 1° spot meters which could meter a golf ball from 100' were available...
My workflow was to meter the Zone 1 (detail above void) shadows (e.g. EV 3) then move the exposure dial so Zone 1 on the grayscale representing the 10-stop range of the #2 print was aligned with EV 3. Then I'd read a Zone 9 (no specular white) highlight in the scene. By consulting the gray scale I knew that with shadows pegged on EV 3 I needed highlights on EV 11 to fit the scene to print with "normal" development. If the highlight reading was EV 12 (one f/stop greater than a "normal" baseline scene. I knew exactly how much to reduce development time to fit the #2 paper based on my initial set up tests.
The Zone System greatly simplified the print making because getting a full rich tonal range was a no-brainer. By front loading the process control Adams made the back-end more or less automatic. I had an enlarging meter set to null the needle at the exposure needed for max. black. I'd meter the blank edge or space between frames, put in the paper and simple as that get a print with a full range. That baseline print recorded, accurately, what the camera saw. That's when the "creative" part started with dodging and burning. Using the baseline print or proof sheet as a starting point you'd plan how to burn and dodge with hands and paddles to vignette the edges, make the face a bit lighter than captured, etc. as now done in Photoshop.
I had the opportunity to compare my results with Adams directly side-by-side. In the mid-80s I was production manager of the USIA publication center in Manila and one day a staff member came into my office with a fiber case and asked: "We got these prints and there's a note that says they are valuable, what shall we do with them?" I looked at the note, saw "Ansel Adams" and said, "You can leave them here."
The USIA magazine "Topic" was doing a feature on Adams and opening the case I found a dozen original prints of his most iconic scenes. While working at me previous job at National Geographic I had reproduced photos from staff photographers and an original Edward Curtis portfolio as full range 4/C sepias for an NGS book on Native Americas, but as a Adams' Fanboy that was as close to heaven as I've gotten so far. To reproduce the Adams photos I used a full range double impression black duotones technique I'd perfected at NGS which retained as much shadow detail as physically possible using analog methods (contact screens and litho film).
How did my prints compare? The paper was the same tone and the max.blacks where the same, and both had all the same tones in between. They were a perfect match technically. Content-wise? That was a different story, but notwithstanding my lack of creativity behind the camera, I do know a bit about high quality reproduction of photos and have understood that a basic requirement to make them seem real is a full-tonal range.
Peter made an interesting observation (and suggested I use better examples) in a side-bar PM about how Adams pre-visualized the result when shooting and would use filters at capture to darken the sky and then dodge and burn when making the print. In terms of actual cause and effect what Adams was doing is very similar selectively adjusting color with Hue/Saturation or styles and adjustment layers in Photoshop: capturing the end points with accurate detail then manipulating what is between them.
Film is engineered with a linear DogE reproduction curve. In layman's terms it looks like the straight line you see when you open a file in curves. If you shoot a gray scale target in a photo it will, with nominal exposure, look the same in the photo. What Adams couldn't do with B&W film at capture is grab the middle of the curve and pull it up or down to change all the mid-tones at capture. What he could do is selectively change how some colors in the scene were rendered as gray tones with filters.
B&W panchromatic film without any filter makes the sky lighter than normal because it has greater blue sensitivity than the eye that looks at the sky and creates our baseline for what normal skin looks like. To correct for that deficiency a savvy B&W photographer always had a yellow filter over the lens. When darker than "normal" seen by eye sky was desired an orange or red filter would darken it. But the same red filter that darken the skies would make any red objects a lighter shade of gray than seen by eye. So if you were shooting purple mountain's majesty above the fruited plains adding a red filter would make the sky darker than normal and the mountains and apples on the trees lighter than normal.
We can get a similar result in digital B&W conversions by altering the channel blending when converting:
Applying styles will have a similar effect as shown on this MacBeth chart with differently ones applied:
Note how in the color files changing the style selectively alters how the colors look relative to each other, but the neutral gray tones remain the same. The "global" contrast remains unchanged (18% gray card will still look 18%) and only the "Zone" values for the color patches are altered when the conversion is made.
In the darkroom Adams could take the 18% gray Zone 5 value recorded on a gray card in a scene, then in the darkroom dodge or burn that area of the negative to change its reproduced Zone value on the print to Zone 6 or Zone 4 as his pre-visualization dictates. I've gone the same with digital files since first bought one in the same way I dodged and burned prints...
On a visit to a historic site I saw and captured this machinery the barn...
but before shooting it visualized this end result...
Had I not been of the mindset due to my Zone System shooting of looking past what I see to what I want the final result to look like I probably would haven't bothered to take the shot.
Same with these ...
The last shot OOC looked like this, which is similar to what I saw with my eyes that morning...
The first shot, taken with my first 2.1 MP Kodak DC290 looked like from the same spot with with lens zoomed wide. It was inspired by Adams shot of Weston sitting under a similar tree but the tree was on a hill. It looks like she is sitting bolt upright, but that's and illusion. I had her bend forward with chin over knees to keep her upper body and camera parallel and minimize near/far distortion. All pre-visualized from this seen by eye baseline...
Digital can't alter rendering of the scene range like B&W to fit the print but there are ways to alter it when shooting. For example by putting the sun at my back outdoors I know the camera will record detail in 95% of the shot because 95% of the content was highlighted by the sun. From that scene fits sensor capture baseline know I can selectively alter midtone values with the adjustment layers as I did in the flat lit shot of my wife fishing above.
The Zone System still has great value as a pre-visualization and communication tool. For example I've seen and participated in many debates over the years about definitions of "correct" exposure, "pure" white, "high" and "low" key, etc. In the Zone System parlance the definition of correct exposure is "get the end points recorded accurately". The stuff in the middle? How you you render than will be baseline "normal" at capture if you use perceptually normal looking lighting strategies.
The possibilities in your photos beyond the "normal" perceptual baseline of how things look in the room you are sitting in are limited only by your imagination and creativity with lighting, posing, finding interesting people to photograph, capturing great expressions and creating the same mood in the mind of the viewer that inspired you to take the shot of the rusty farm implement or broken down outboard motors.
White? If I told someone to expose a shirt to make it white that is subject to their interpretation. Do you want the highlights Zone 10 specular white, Zone 9 solid "paper" white (how paper looks in a photograph when seen on a white background like the print paper), or Zone 8 or 7 shaded white? .Shoot someone in a white backlit shirt and different parts of the shirt will fall on Zones 9, 8, 7, 6 and 5. With the lexicon of the zone system you can precisely instruct some one how to take a baseline image of the white shirt and selectively dodge and burn to achieve those values. That's how Adams was able to delegate the job of printing to assistants — he gave them a blueprint for the final image in the form of a tissue overlay or a marked up "baseline" proof from the negative.
Let's revisit this studio image...
The advantage in the studio is always being able to fit everything to the sensor range by adjusting light intensity of rim light, key, fill and background; the four basic ingredients. Like cooking how the dish turns out depends on how well you can cook. Whether is is a perfectly executed fried egg or a 5-star exotic dish will determine how the critics like it. To some nothing is better than a perfectly cooked egg
The shot above recorded the camera "normal" in that lights were adjusted to record detail everywhere. But had I not opted to use the rim light, the same ratio of key and fill would not have worked. The fact that I backlit and wanted those backlit areas to be the brightest thing in the image and retain detail required me setting the rim light to create a Zone 9 white where it hit. That in turn forced me to "underexpose" the whites in front with key light darker that I would have without the rim light, on Zone 8. Had I not used the rim light I would have needed to place the highlights hit by the Key light on Zone 9, not 8 because without the rim light Zone 8 would look abnormally dark.
That's what I meant by "Beyond the numbers..." I'm in complete agreement they don't matter and that is why I don't use a meter. Like everyone I bought one when I got studio lights because I thought it was necessary only to find I could live without one. I shot with speedlights for 30+ years without one not using ratios, simply moving the key and fill until they recorded a full range of tone on whatever I was using to record the image: B&W film, color neg., transparency, digital my goal technically is fit the scene to print, and creatively to make it look on the print how I imagined it, not how my eyes saw it. For conventional portraits however what I want is more or less what I see... That why they are conventional.
I set up a target, get the ends of the scene both exposed accurately then play with the middle by eye until it looks "right". I just happen to like convention portraits more than some of my critics.
In terms of technical cause and effect adding the rim light changes the PERCEPTUAL BASELINE FOR WHAT LOOKS "NORMAL". In the backlit shot it looks normal to have key key lit whites an off-white Zone 8 because that's how backlight is perceived in person. I could have placed the rim light on Zone 10 (specular - 255) and the key lit front on Zone 9 (solid - 250) but I did not want the rim lighting to blow out detail where it hit the clothing or skin of the subject who would replace the target a few minute later.
I don't measure rations any longer or thing in those terms (except to communicate how to set lights) but for those who do set lights via metered ratios consider how they would change numerically had I measured them. The shadow tones controlled by the fill would be the same whether or not I used the rim light. If I started without the rim light I would have adjusted Key for Zone 9 white in front. If I afterwards decided to add the rim light and also keep it at Zone 9 white below clipping it would not contrast. So I must lower the key light, relative to the constant fill, changing the numerical ratio of key:fill. What was the Zone 9: Zone 1, key:fill ratio before the rim light was added now becomes the Zone 9:Zone1, rim light: fill ratio with the key:fill ratio becoming slightly less. Yes that can be computed and set with a meter, but it is far simpler to set it visually to the end points, then adjust the balance in the middle, controlled by the key light in that case, by eye until it looks "right".
The creative part that occurs between your ears is executed in the space in the image between the accurate rendering of the lightest and darkest detail in the image. The middle tones are your creative playground. You can play with them with the lighting or your can play with them in post processing but to look real the final result will, ideally, have detail in the shadows and highlights. What looks "right" is always relative to your creative goals for the shot. If my goal was to make the kid look like he had been shot of cannon and flying in mid air with a set of bagpipes in close pursut I would had suspended him from the ceiling with wire, turned on a fan and lit him differently, but the photo would have the same full tonal range.
Yes it's OK to blow highlights and eliminate detail where expect in shadows for creative reasons, but while some of the artistic inclination may think that brilliantly creative (because its different) other more technically oriented viewer like me will thinking, "nice creative shot, all 10's for that, but I wish he was more technically competent..." Those two different world views seen in most forum threads like are a reflection of the fact we have different temperaments (personality types) and experience.
Call me old fashioned but much of what is trendy in photography today such as flare, blown highlights, exaggerated contrast looks very similar to all the defects I worked hard to learn to eliminate from my images and remarkably similar to the technically incompetent work of the "Uncle Joe's" the pro's complain are putting them out of business. 
Edited on Nov 21, 2011 at 07:03 PM · View previous versions
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