Zone System
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This page summaries my research into how to use the Zone System, especially in digital photography. I never used the system in the old days as I did very little darkroom printing, but I thought I understood the idea - but not enough...

The Original Film Zone System

Zone descriptions. (Adapted from Adams 2002, p. 52-60) - Film and Paper.

Spot Zone

Description

  0 Total black. Complete lack of density,other than dark current noise.
Should appear as total black in the print.
I Near black, no detail. Effective threshold. First step above complete black in the print.
Slight tonality, but no texture.
II First suggestion of texture. Very dark details in shadows.
Deep tonalities, representing the darkest part of the image in which some slight detail is required.
Shadow III Very dark grey. Dark textured bark on shadow side of tree. Average dark materials.
Good texture and detail can be seen.
This is where you will want to place shadow details.
  IV Medium-dark grey. Average dark green foliage, shadow side of skin, dark stone, landscape shadow. Details plainly visible. This where you want to place the shadow side of Caucasian portraits in sunlight.
Average V Middle grey. Standard Kodak 18 % grey reflectance card. Clear northern sky, dark skin, grey stone, average weathered wood.  Excellent detail visible.
  VI Rich mid-tone grey. Caucasian skin in sunlight, light stone and sand, shadows in snow in brightly sunlit snowscapes. Sharp fine detail visible.
Highlight VII Off white or bright light grey. White with texture, very light skin, silver hair, weathered white paint, snow with acute side lighting.
Highest Zone that will still hold good details.
  VIII Almost white (not blank whites). Textured snow in sun, reflected highlights on Caucasian skin. Delicate texture and some gradation exist, but no detail.
IX Nearly pure white without texture (must be compared to pure white to tell difference). Glaring white surfaces, snow in flat sunlight.
No detail or significant texture visible.
X Pure white. Specular highlights, glares or light sources in the picture area. Rendered as the maximum white value of the paper surface
 
There is general confusion in books and on the web about whether Zones represent f-Stops or not. 

Nearly everybody says... Zones are one-stop changes in exposure

As Russell Cottrell in Beyond the Digital Zone System (which also contains a lot of useful information on the D700) says

If one meters a subject and then increases the exposure by one stop, we call this placing the subject on zone VI.

But, for instance, Gisle Hannemyr in Adapting the Zone System to Digital Photography states...

Many texts on the zone system claims that the difference between adjacent zones are 1 EV (1 f-stop). This is not true.
EVs and f-stops express relative difference in levels of light present in a scene.
Zones express relative difference in levels of density present in a photographic print, which may or may not reproduce exactly the relative levels of the original scene.

And Chuck Gardner in his The Adams Zone System and Digital Photography says...

The Zones = f/stop confusion stems from the fact Adams' baseline "normal" sunlit scene measures 10 f/stops and his baseline #2 print paper needed a 3.0 density range (i.e. 10 stop equivalent) negative range.

Zone Concepts

So we need to make sure we understand the concepts before seeing how the system applies to digital photography - to take a few quotes...

All aspects of the system are based on the artistic premise that the photographer should make some decision about how the photograph should look before the film is exposed. In other words, Pre-Visualisation means imagining the final print before the film is exposed and deciding how we want it to look.

The Zone System is based on the principle that the correct exposure is a matter of personal, creative expectations and that a light meter is a tool to use for information.

We should distinguish between print values and negative film values because the print value is a literal grey tone while any area of the negative can be printed in any tone by changing the exposure time given to the print.  The negative film values are relative to each other and the print values are absolute.  Remember that the zones in Adams' system are tonal values on the print, not in the scene.

When we talk about a tree being in zone V, we mean that it is either zone value V on the print or we have exposed the film with the intention of making it zone V.

Changes in development from normal alter the zone relationships and the progression of zones is no longer considered normal.   

When the film is developed for more than the normal time we get more than a one zone change for every f-stop difference that we measure.

Less than normal development results in less than a one zone change for each measure f-stop difference.

The above points were the foundation of the process as film development time changes the dynamic range of the negative (moving zones apart or closer) - something we can not really do with digital 'negatives'. This zone 'moving' made the rest of the system work for B&W prints.

A point to remember

In the old days the post-processing was really done blind compared to today's facilities.  One had to get the exposure right, so that everything else could be controlled. 

It still applies today that if the exposure does not capture the detail you want, no amount of post-processing can get it back.  The worse case being clipped highlights - once they are blown, they are blown!

A bit of detail (no pun intended!)

Talking about 'detail' is not the same as 'seeing', so I've taken following images (and the ones above) from "The Practical Zone System for Film and Digital photography" by Chris Johnson, which is free to download from the web and well worth the read.  I also read "The Zone System Craft Book" by John Woods and some of the quotes are from him - it is a good 'film' perspective read.


Zone I

Zone II

Zone III

Zone IV

Zone V

Zone VI

Zone VII

Zone VIII

Zone IX

The Important Zones

We usually meter to place one of the zones III, V and VII.  I feel that it is the texture detail in zones III and/or VII that are the most important areas to decide to capture.  It is not always obvious (to me) which are the important areas in a scene and I must 'confess' to sometimes finding 'eye-homing' areas when post-processing that I was not aware of when I took the photo.

In the film days the 'rule' was

Expose for the shadows, develop for the highlights

In the digital world, beset by clipping problems (especially highlights), the 'rule' now becomes

Expose for the highlights, process for the shadows

By making test exposures we can formulate rules to ensure that on metering, say Highlights, we can correctly expose the image to capture as much detail as possible by dialling in some compensation - an alternative is to check for clipping highlights, on the camera screen, after taking a shot, but beware this is not foolproof and does not relate to detail present in raw capture.

 

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