Part 1 Beauty and the Sublime: Exercise 1.8: Zone System in Practise

Wikipedia quotes "The Zone System is a photographic technique for determining optimal film exposure and development, formulated by Ansel Adams and Fred Archer"

https://en.wikipedia.org/wiki/Zone_System

Adams  distinguished among three different exposure scales for the negative:

• The full range from black to white, represented by Zone 0 through Zone X.
• The dynamic range comprising Zone I through Zone IX, which Adams considered to represent the darkest and lightest “useful” negative densities.
• The textural range comprising Zone II through Zone VIII. This range of zones conveys a sense of texture and the recognition of substance.

The Zone Scale:

The Zone Scale and its Scene Relationship

Exposure Technique

A dark surface under a bright light can reflect the same amount of light as a light surface under dim light. The human eye would perceive the two as being very different but a light meter would measure only the amount of light reflected, and its recommended exposure would render either as Zone V. The Zone System provides a straightforward method for rendering these objects as the photographer desires. The key element in the scene is identified, and that element is placed on the desired zone; the other elements in the scene then fall where they may. With negative film, exposure often favours shadow detail; the procedure then is to

1. Visualise the darkest area of the subject in which detail is required, and place it on Zone III. The exposure for Zone III is important, because if the exposure is insufficient, the image may not have satisfactory shadow detail. If the shadow detail is not recorded at the time of exposure, nothing can be done to add it later.
2. Carefully meter the area visualised as Zone III and note the meter’s recommended exposure (the meter gives a Zone V exposure).
3. Adjust the recommended exposure so that the area is placed on Zone III rather than Zone V. To do this, use an exposure two stops less than the meter’s recommendation.

Each zone has an difference of 1 exposure stop therefore Adams'z zone has a dynamic range of 11 zones therefore 11 stops

The Cambridge in Colour camera metering tutorial is very helpful and can be found here:

http://www.cambridgeincolour.com/tutorials/camera-metering.htm

A digital camera's metering system will try to determine a scene's average exposure calculation and expose for Zone V, or 18% grey as many may notice is the colour often inside a photography book (certainly it is for some of Freeman's) and also the colour for many lens cloths).

In my early days with a camera I wondered why I couldn't capture sunset seen by my eyes on my camera. Of course I know understand this to be the fact a camera's sensor is not as good as the human eye in terms of dynamic range. I suspect in the future this may change as technology increases. Creative options were to use spot metering and expose for the sun, and under expose any foreground, or expose for the foreground and over expose the sun. My experiences and HDR experimentation as part of my DPP course would now suggest another option is to take 3 images where:

i) expose for the scene average

iii) then expose for the sun

iii) then expose for the foreground

Taking these images with the camera on a tripod would allow me to combine all 3 images and create a HDR (high dynamic range) image. Adjust to exposure also would allow me to be creative and perhaps on purpose put for foreground into silhouette subject to my pre-visualisation of the image I wanted.

Adams' technique then is identify from a scene the darkest area from which detail / texture is required. Meter this element of the scene, in the digital world I can use the spot meter facility on my camera. This exposure reading would effectively allow me to determine this element of the scene as the middle grey, ZONE V.

The technique then of Adams is to reduce the exposure by 2 stops e.g. reduce shutter speed, decrease aperture size. This then places the "the darkest area from which detail / texture is required" onto Zone III

A reduction of 2 stops of light is to reduce the light hitting the sensor by one quarter (reduction of half the light is a reduction of 1 stop of light)

How to do this in practise

I think my general rule of thumb is:

Aperture

Each change in aperture represents a change in half a stop of light

Shutter Speed

Each change in shutter speed represents one third a stop of light

ISO

Each change in ISO represents a stop of light

So having metered the Zone III area of your scene using the spot meter of the camera which will give you an exposure reading of Zone V, to make the camera expose it as a Zone III reduce the metered reading by two stops of light by:

1. Increasing the aperture by 2 stops (apertures of the lines are likely 1/2 stop difference so that's 4 clicks to a smaller aperture / larger aperture number)

2. Increase the shutter speed by 2 stops (the camera shutter speeds are likely 1/3 stop difference so that's a shutter speed increase of 6 clicks)

3. Decrease ISO by 2 stops (that's 2 clicks of adjustment on ISO to a SMALLER number)

I personally think the easiest way to do this is if it gets confusing is:

a) take a spot metered reading of the Zone III area with camera ISO and its normal level

b) set your camera to manual, and set aperture and speed as metered

c) adjust the exposure option of the camera and reduce it by 2 stops

Of course using the histogram which will measure the darkest black as 0 and the brightest white as 255 will display a graph to show where the captured elements of light register on this scale and its fairly easy to tell where a scene has clipped highlights or low lights. Adjusting exposure to ensure no highlights are clipped is a simple way of capturing a scene and ensuring no elements are overexposed since these cannot not be recovered post processing, but underexposed details may be recovered.

The problem maybe with this approach of using the zone system is that you are at risk overexposure in some areas in the attempt to keep detail where you want it

Exercise

Produce 3 images taken in relatively high dynamic range conditions. Make sure the exposure choice renders as much detail as possible in the brightest and darkest areas of the the photograph

Image 1

This autumnal tree was an excellent example of a scene with a high dynamic range. DXO advise that in a landscape scenario the Nikon D700 has a dynamic range of 12.2 stops. In adjusting the exposure to ensure I maintain the detail of the tree trunk and branch filigree I have anchored the histogram at zero with no clipped lowlights. The dynamic range of this scene is to much for the camera sensor and I have clipped highlights of sky in between the leaves. This is shown on the histogram as well as Photoshop's highlight clipping display in the RAW previewer. As you can see in the scene the highlight clipping is minimal as a distraction and also shown on the histogram as having low amounts of the image capturing highlights. In this instance given the "limitations" of the camera having most of the the detail of the trunk captured is an acceptable price to pay for the small elements of highlights in the sky clipped but with minimal presence.


Image 2

This image has a wide dynamic range (DR) but appears smaller than image 1, the key contrast between the white buildings and the green trees. Had the DR exceeded my camera's range then I would have need to ensure no highlights were clipped in the buildings which are the focus of the image. In this instance decreasing the shutter speed to 1/640 keeping the aperture at f/8 (which I believe to by the lens sweet spot and ideal for a landscape image with back to front focus) the DR of the image has been kept within the 0-255 range of the camera's sensor. This day was overcast hence the smaller DR of what would have exceeded the camera's range with the contrast between the white buildings had they been lit brighter by a stronger sun.

Image 3

In this image I've used the river in mid foreground using the spot metering and then under exposed two stops y=using the exposure controls. However the resulting image of the scene looks poor but I wonder if this put the river into Zone 3

Using Silver Efex Pro and using the Loupe and selecting Zone 3 it has highlighted the river (red/orange) and elements of the trees top left.

This proves Zone system process but the resulting image exposure is poor. I expect that this is because the dynamic range of the scene is much greater than 10 stops.

I the Adams Zone system is a good way to ensure the detail of what you need exposed at Zone 3 with sufficient detail but this may need to be combined with either:

a) images created using the histogram
b) images created using combined exposures

Of course each scene and dynamic range will be different and the intended result related to the photographer's vision, however having multiple options, especially for landscape where the photographer has the time, in the digital world taking many images is not going to be a problem and gives the photographer greater options and opportunities to produce the image how he wishes.

Digital post processing allows greater opportunity of exposure adjustment with such ease. I wonder how Adams images and workflow may have changed in the digital photography worl we are in today