Ansel Adams’ classic ‘Zone System’ remains relevant both technically and aesthetically for today’s digital photographers.
The foreword to the 1981 publication of The Negative, the second volume in The Ansel Adams Photography Series, which outlines the techniques and procedures developed by the renowned photographer over his working life, states:
For Ansel Adams the art of photography and the practice of its craft were integrally linked. The transformation of a visual encounter with the world into a memorable photograph is the essence of what every serious photographer wants to achieve. A successful photograph is the product of a sensitive and receptive mind and a well executed sequence of actions in the field and darkroom.
It’s a message contemporary photographers should take to heart.
Adams is famous for his Zone System, a method developed for silver halide photography in collaboration with Fred Archer at the Art Center School in Los Angeles. It is based upon the characteristics of black and white films and printing papers available at the time and involves both exposure and chemical development.
In The Negative, Adams emphasises the relevance of the Zone System to technique and craft as well as creativity, describing it as ‘an enabling system to liberate, not restrict, the creative photographer’. The function of the system lies in applying it to achieve a visualised image, with few, if any, limitations on how the visualisation is achieved.
We’ve added tags to these two digitally-captured images (B&W and colour) to show how their tonal ranges can fit into Ansel Adams’ Zone System classification (outlined below).
Writing in the revised 1981 edition of The Negative, Adams foresaw the introduction of ‘the electronic image’ as ‘the next major advance’ in photography. What he didn’t predict was just how different the materials and techniques we use would become from those used in his heyday between 1930 and the mid 1950s.
Fortunately, some aspects of the Zone System are as relevant to today’s photographers as they were when B&W materials dominated the scene. In this feature we’ll look at the basic structure of the Zone System, the technical differences between B&W materials and digital media and how Adams techniques can be translated for contemporary usage.
The Zone System
The Zone System spans a 10-step scale of tonal values from Zone O through Zone X in which Zone 0 represents the deepest possible black and Zone X the brightest possible white (usually the white of the paper base) in the image. Zone V represents the mid-point, while Zones I to IX represent ‘the limits of the real value scale that convey the full range of texture and substance’ in the image.
Here’s a brief description of each of the zones (with examples in brackets):
Zone 0 – Black with no detail or texture
Zone I – Near black with no visible texture or detail (deepest shadows)
Zone II – Very dark grey with the possibility of slight texture (deep shadows, ‘black’ hair)
Zone III – Dark grey with visible texture and detail (dark textured bark, shadowed side of tree)
Zone IV – Medium-dark grey with obvious texture and details (dark green foliage, shadowed Caucasian skin)
Zone V – Medium grey with excellent visibility of details and texture (clear dark blue sky, average setting for exposure meters)
Zone VI – Mid-tone grey with sharp, fine details visible (light-toned clouds, shadows on snow)
Zone VII – Bright light grey (weathered white paint, ‘silver’ hair)
Zone VIII – Light grey-white with texture (minimal) but no details (‘white’ clouds, textured snow in sun)
Zone X – Reproduces as paper base white, no image recorded. In a print, will appear as specular highlights.
This diagram shows how the Zone System is distributed with respect to the visible tonal range from the darkest black to the brightest white and compared the dynamic range that can be recorded and printed plus the tonal range across which textures can be reproduced. (Copied from page 52 of ‘The Negative’ by Ansel Adams.)
Visualisation
The key to using the Zone System lies in being able to visualise how the scene in front of you will translate into a final image. This ‘visualisation’ refers to ‘seeing’ the scene as a range of brightnesses (luminances) and evaluating how that range can fit into the medium chosen to present the image to a viewing public. There’s a lot to take in from that statement.
In the first place, a photographer is essentially recording a three-dimensional subject in two dimensions, in effect ‘flattening’ it. Secondly, the tonal values within the scene are likely to be much greater than the display medium can handle, especially when the image is printed (less so when it’s displayed on a screen). The purpose of visualisation is to anticipate the controls that must be applied to reproduce the scene – and these will differ, depending on the medium on which the image will be viewed.
Digital photographers are more fortunate than Adams and his contemporaries because they can call up histogram displays to show the tonal ranges in the subjects they photograph. These graphs make valuable aids, particularly for positioning the mid-tones in the exposure in order to produce a reproducible picture. (Fortunately, today’s OLED viewfinders replicate the hues and tones the image sensor records, so what you see in the EVF is what gets recorded in the image file.)
The histogram display for this image shows it exceeds the 0-256 step tonal range the camera’s sensor can record. We’ve indicated the two Zone System extreme values, with an X showing highlights that have ‘blown out’ to bright white and an O indicating shadows that have ‘blocked up’ to black. No details are recorded in either area.
Where the photographer wants to record details in the clouds, the exposure level should be reduced until this area falls within Zone VIII (where texture is just visible). Unfortunately, given the nature of image sensors, this is likely to increase the area in which shadows are ‘blocked up’.
Blocked-up shadows will be less problematic if you’re working with a 12- or 14-bit raw file, which captures more information than an 8-bit JPEG. Shooting a raw file should enable you to record a wider dynamic range, particularly in shots taken in bright outdoor lighting. But you must ensure the exposure is correctly positioned; and that’s where visualisation and the Zone System can be of real assistance.
In Ansel Adams’ Zone System, you would expose to maintain shadow detail, then develop to place highlights in the zones of your choosing. With a digital camera, you expose to obtain details in the highlights and then process your raw files to bring up shadow details.
Some cameras make this easy with highlight-weighted metering modes that ensure highlights are not blown out or overexposed. Others provide HDR (High Dynamic Range) modes (see below) to deliver an image with an extended brightness range.
If your camera lacks these functions, use of spot metering to measure the brightest highlights in which you want to retain visible details will let you adjust the exposure accordingly. It’s important to record these details because, unlike film, digital sensors have an absolute cutoff at the highlight end of the exposure scale; so details that fall into Zone X will be lost.
When you can’t use spot metering, try setting the exposure compensation to under-expose (minus values) by between 0.3 and 1.0 EV when metering with the multi-pattern or centre-weighted average modes. A quick check of the camera’s histogram will show you how far to go. If the graph rises sharply at either end of the X (horizontal) axis (as shown in the illustration below, you’ll know details in highlights or shadows haven’t been recorded.
Dynamic range considerations
In Australia, it’s not uncommon for outdoor scenes in bright sunshine to have dynamic ranges in excess of 2300:1 (equivalent to approximately 11 stops or about 11 bits). In a JPEG image, this range must fit into an 8-bit scale with 256 steps, which is the range reproduced in a camera’s histogram display.
These two images illustrate the differences in the dynamic ranges recorded in raw and JPEG files. The raw image at the top records the full subject brightness range, while the JPEG image below it shows clipped highlights and shadows.
Unfortunately, prints on paper can only reproduce a brightness range of about 100:1, or six to seven stops. So the histogram should only be seen as a rough – although very useful – guide to how the tones in a scene will actually reproduce in a print.
Typical computer screens and TV sets have dynamic ranges of at least 1000:1 (10 stops), although the OLED screens used in many camera EVFs are even wider. But they’re not as wide as the latest DisplayHDR 1000 screens, which can encompass a total contrast ratio of 20,000:1. These figures explain why images taken with smartphones and basic cameras will look good when displayed on screens but often produce disappointing prints.
The Zone System and HDR
High Dynamic Range (HDR) shooting modes usually involve rapidly recording between three and nine frames captured at different exposure levels and then combining them in the camera to produce a single frame. The resulting image (usually, but not always, in JPEG format) is composited from the best-exposed sections of each frame.
HDR capture aims to overcome problems associated with fitting scenes with extended brightness ranges into outputs with relatively short dynamic ranges, which is also one of the objectives of the Zone System. Both involve compromises but, where the Zone System required the photographer to think carefully about where to ‘place’ each exposure and how to process the film, HDR shooting often takes a more scattergun approach and includes potentially unusable frames with little or no image data at each end of the tonal scale. An example is shown on this page.
This sequence shows a seven-frame set of exposures for an HDR shot. The sequence begins with a ‘correct’ exposure to enable the camera to gauge the exposure range to cover. Note that the darkest and lightest frames in the sequence provide little or no worthwhile details.
This image is the result of the HDR sequence shown on this page. Some dodging of highlight areas was needed to prevent the shot from looking a little ‘flat’.
Photographers who can visualise tonal values and assess exposure levels using a similar strategy to the Zone System often find they can obtain better end results when shooting and processing raw files from their camera – as long as the highlights haven’t been over-exposed. The higher bit depth of raw files (12- or 14-bit compared with 8-bit for JPEGs) records a wider dynamic range and provides more scope for additional adjustments to bring up shadow details and modify brightness, both locally and globally, with the dodging and burning-in brushes. Contrast and saturation in the image can also be adjusted over a wider tonal range.
This picture was originally captured as a raw file and converted into a 16-bit TIFF file for editing. Minor dodging of highlight areas was applied to slightly boost the overall impact of the image.
Article by Margaret Brown (see Margaret’s photography pocket guides)
