Written by Simone Angarano
In this issue we are dealing with the topic of the Zone System. It had been devised by the famous photographer Ansel Adams and Fred Archer in the 30s, about a century ago.
Adams wanted to make a reliable and reproducible system to find ‘the best exposure’ regardless of any lighting conditions.
But is this system still valid in the digital age?
In order to answer this question, it is necessary to shed light on the reason why this system was born and what the real fields of application were, and to evaluate whether some of the basic principles are still valid today.
It must be said that we will not go into all the details of the zonel system in this article. Please consider that Adams wrote 3 books about it, The Camera, The Negative and The Press, so for those who want to deepen into the subject these are definitely 3 cornerstones to own.
Let’s go back to the answer of our question; when Adams developed the Zone System he made it mainly for black-and-white photography and the development was handled separately for each individual frame; in fact, his photographs were almost taken on large format plates.
In this way it was possible to uniquely develop each negative. This turns out to be a first similarity with digital photography. Thanks to post production softwares, modifications to negative files can be applied to each single shot.
In the previous lines we wrote that Adam’s aim was to have a reliable system, which allowed to foresee the rendering of the brightness range of a scene when printing.
In order to make it happen, Adams split the brightness scale, which was classified from a black without detail to a burnt white, into eleven grey levels, called E values, numbered by Roman numerals from 0 to X.
These values are assigned certain zones on the negative (that’s why it is called Zone System).
Therefore, zone 0 on the negative corresponds to the value 0 in print, and so on for the other numbers.
The V Zone corresponds to the average grey of the exposure meter.
The unit of measurement of deviation between one zone and another is the same as the one used in photography, that is 1 Stop
According to Adams the 0 and the X zones shall never be used because they are unnatural.
The I and IX zones are used to mark contrasts, that is the classic accents, the II and VIII zones are high lights and deep shadows.
The III and VII zones are the most detailed ones where the medium greys are located.
In short, when Adams used silver crystal negatives, he considered essential to expose for shadows using a spot meter. By reading the shadow the exposure meter will indicate the time/aperture setting and will put the spot in the shadow in the V zone (which corresponds to an average grey).
Knowing that it’s about a very dark shadow but still with some details, it will have to be relocated in the III zone. So in this simple way all you need to do is to underexpose by two levels the initial value.
Like a domino all the other zones will fall into the others according to the barycenter we chose; of course you have to check if this drop is compatible with the picture we want to create.
It must be said that in order to increase the dynamic range of films, Adams used to expose the shadows and developed the lights due to the chemical reaction of the silver salts on the negative, which turns out to be not linear.
The consequence is that in the analogue field you can compress or extend the tonal range of the highlights on the negative (within certain limits) by manipulating the development times.
This system can be applied in an extremely effective way also in the digital field; our raw file allows you to push or pull the development as in the film negative through the curve management of our photo editing software.
The principle is the same: we fix the exposure on a carefully studied barycentre according to the image you want to obtain and then you play with the development so that the tonal range falls as you want to.
Shall we apply all that Adams asserts also to the digital field? NO!
You can only do this if you reverse the roles between light and dark tones!
With the analogue negative the exposure has to be done for the shadows and the development calibrated according to the highlights, whereas in the digital the order is reversed: you have to expose for highlights, and then develop for shadows.
This is why in the digital field it’s easier to retrieve the shadows and the tonal richness is at its best in light tones.
In the end it would be enough to expose for highlights, of which the exposure meter will indicate the value V and so as a consequence just overexpose it by two levels in order to take it to zone VII.
If you are interested in more information on this topic, please write us.