Proposed for precision exposure metering with the digital camera.
About the Zone System of Ansel Adams: Ansel Adams was a great landscape photographer, scientist, and writer in the 20th century in the USA. Fred Archer was a great portrait photographer in Hollywood. Ansel Adams and Fred Archer jointly formulated the Zone System in the middle of the past century (1939- 40). The zone system helps a photographer to find out the perfect exposure of subjects of different colors and brightness. It also helps to calculate (to average) a precise exposure for critical lighting conditions. At that time, digital photography did not exist. They (Ansel Adams and Fred Archer) divided the tonal gradations into eleven different zones (zone 0 to zone X); from the blackest black to the whitest white.
I reconstructed the zone system of Ansel Adams to make it affordable and easier with digital photography; especially with compensation steps found in digital cameras.
I divided the tonal gradations into 7 steps in place of the eleven steps of the zone system of Ansel Adams. I placed my zone 0 instead of zone 5 (V) of the older one. I placed my zone -3 (minus three) in place of zone 0 of the older one and my zone +3 (plus three) in place of zone X of the older one.
It’s easy, but be attentive
Before trying the zone system one should have enough knowledge and practice about the following things:
1) Exposure and its factors; aperture, shutter speed, ISO, and light.
2) Exposure modes; manual, shutter priority, aperture priority, and program.
3) Metering modes; matrix (evaluated), center-weighted, spot, partial.
4) Brightness range of the area in composition.
5) Exposure latitude in digital imaging in Raw and Jpeg format found in different digital cameras.
6) Manual and auto exposure compensation.
7) Incident and reflected type metering. How reflected type metering is wrongly influenced by subject color.
You will really understand this new Zone System if you read my article attentively and try it with your camera.
The Digital Zones (Reconstructed)
In digital photography Red-0, Green-0, Blue-0 means such black that it cannot be darker anymore.
Red-128, Green-128, Blue-128 means such neutral grey that falls in the middle point of black and white, which may refer as 18% grey or mid neutral grey.
Red-255, Green-255, Blue-255 means such white that it cannot be whiter anymore.
To understand digital zone let us assume that we are living in such a planet where all objects are in black and white, i.e. in neutral color. As a result, no matter whatever photo we take the value of red, green and blue are always equal. Now let us try to understand the histogram bellow: (Figure 01)
If you take a photo of a mid-grey cloth with correct exposure, its histogram will be presented on the 3rd line. Camera exposure meter generally does not make mistakes while calculating exposure for this type of mid-grey object. Figure-02.
Now if you take a photo of a nearly black cloth showing its texture, its histogram should appear near the 1st line (a little on the right side of the line). Figure-02.
Similarly, if you take a photo of a cloth whose brightness falls between black and mid grey then its histogram should be presented on the 2nd line. Figure-02.
Again if you take a photo of cloth whose brightness falls between mid-grey and white, its histogram should be presented on the 4th line. Figure-02.
Finally, if you take a photo of a white cloth showing its texture and fold marks then its histogram should appear near the 5th line (a little on the left side of the line). Figure-02.
Built in meter in the camera has a tendency to push any brightness of subject on the 3rd line in the histogram or in other word to make it as bright as mid grey. But we want to achieve black object as black and white object as white in our photo. Fig-03.
If we take photo of white board with exposure calculated by the camera meter, then it will appear on 3rd line in the histogram presenting it as mid grey. It is seen in experiments that if we set the exposure two stop over (for example F4 instead of F8) on the exposure offered by the camera, then the white object is represented against 5th line (a little on left side of the line) in the histogram. Now we get white object as white in the photo. But to keep the textures in white object (if any) it is better to set 1 + 2/3 stop over (for example F4.5 instead of F8) instead of pushing it to full two stop.
If we take photo of a board whose brightness falls between mid grey and white with one stop over (for example F5.6 instead of F8) on the exposure offered by the camera, then the object is represented on 4th line in the histogram, just as we want.
Similarly if we take photo of a board whose brightness falls between mid grey and black with one stop under (for example F11 instead of F8) against the exposure offered by the camera, then the object is represented on 2nd line in the histogram, just as we want.
Now if we take photo of a board is black but not dark black, i.e. some textures in it are visible with two stop under (for example F16 instead of F8) against the exposure offered by the camera, then the object is represented against 1st line (a little on right side of the line) in the histogram, just as we want.
If we can achieve the correct brightness in the photo by adjusting the exposure offered by the camera meter (called compensation) then it is also possible to very nearly reproduce correct brightness of all color in the world. For this we just need to see the world in black and white at first.
Let us now try to imagine things around us in black and white and try to match them against the 5 lines of histogram (see the diagram in the next page, Figure-04). Here Digital Zone 0 is assumed equal to Zone 5 of Zone system (by Ansel Adams).
We will see the correct exposure and histogram for some of our well known object. See the diagrams in the bellow. Fig-04, 05, 06, 07.
It is assumed in the above cases that there are no other dark or bright objects except for the mentioned objects under a constant lighting condition.
Correct brightness will be produced in the photo if controlled exposure is set for each object according to the zone. Digital Zone system will be highly effective in case of spot metering. When photographing an area consisting elements of different brightness, then photographer can judge the elements or parts of the elements with their respective zones (-3 to +3) and then set an exposure to acquire most of the tonal values (shadows to highlights) in the photograph.
Cautions
1) Use spot metering of your camera or a spot meter of handheld meter during measuring reflected light values in the scenary.
2) Zone system is not sugested in cases like
a) Light values changes continously within moments.
b) Candid shots, where presetting is not possible
Setting Manual Exposure Compensations in Manual Mode (M)
Compensation during Auto Exposure
Camera meter will try to yield mid grey brightness in the image for all levels of brightness in the subject even when the mode is set to Aperture Priority Auto (A), Shutter Priority Auto (S) or Variable Program Auto (P).
In auto exposure full frame white object will become mid grey. In this situation white objects will become white if the camera compensation is set to two stop over +2. Following is a chart showing how much compensation is needed for which object in full frame-
| Digital Zone -2 | Black cloth | Compensation -2 |
| Digital Zone -1 | Dark green leaf | Compensation -1 |
| Digital Zone -0 | Average skin tone | Compensation 0 |
| Digital Zone +1 | Bright skin tone | Compensation +1 |
| Digital Zone +2 | White cotton | Compensation +2 |
Compensation should be set back to normal (0) after taking photo of such objects with compensation. Otherwise incorrect result may occur while taking photo of other objects.
Some Sample Images
In this scene the main beauty is the highlight detail of the cloud. I preferred highlight detail of the clouds than shadow detail of the trees. I used spot metering on the brightest areas of the clouds. It measured F32 (ISO-100, Shutter Speed-250). I set back the aperture to 16, two stop over; as I considered it as zone+2. Finally I set aperture 18 (1/3 stop under) to save most of the highlight details. At that time the trees showed unlimited under exposure, which became black in the final photograph.
Here the brightness most of the parts of this scene is equivalent to mid tone, that is zone0. So no compensation needed. Matrix, centre weighted or spot may show same exposure reading.
Here the brightness of the bright green area is considered as zone0. Then the blue sky showed one stop over exposure (zone+1). Trees in the shadow areas with no detail (complete black) is now considered as zone-3.
Here the brightest area of the back lighted flower is considered as zone+2. I set two stop over exposure than the exposure shown by spot meter at the brightest part.
Here I put my spot meter on the white cloud. Considering it as zone+2, I put two stop over exposure than I got from the meter. When I put my meter on the blue sky, meter showed one stop over (as zone+1). When I put my meter on the iron made structure. it showed one to two stop under exposure. In the photograph we can see detail in the structure.
Setting exposure for a view is like putting a stick in a box of limited length keeping eyes nearly closed, but having some clues. If you know the centre of the box and also the centre of the stick you can easily put a 4 fit stick in a 4 or 5 fit box. Compare mid of the box with zone. If the stick is 7 ft and the box is only 5 ft, then we have three options. One: cutting both sides of the stick. This is like loosing both the shadow and high light detail in your composition. Two: cutting the lower side of the stick. This is like loosing the shadow detail in your composition. Three: cutting the upper side of the stick. This is like loosing the high light detail in your composition.
When we go to shoot a view with extreme brightness range, where all the details cannot be accommodated in an image, we have to decide which side or sides (shadow/high light/both) to be preferred. Zone system can help a photographer to execute his decision very perfectly.
Zone system also helps us to reproduce the tones of the picture elements brighter or darker intentionally and precisely. If you want a mid tone to become nearly white, just set the exposure two stop over. If you want a mid tone to become nearly black with detail, just set the exposure two stop under.
Author: Rafiqul Islam
