Sunday, December 6, 2009

Exposure and Processing

This is what the Zone System was designed for to control the contrast of the negative through exposure and processing. The aim is to expose for the shadows and develop your film for the highlights.

Your exposure for negatives should be for the shadow area that you want to have detail on your print. So if you want the shadow to have more detail you use wider aperture (smaller f stop) and a slower shutter speed. And less detail use a smaller aperture (larger f stop) faster shutter speed.

Your processing for the negative should be for the highlights and it's overall contrast. The film's development time will determine how white or grey the lighter areas of your print will be. To state the obvious if you over develop or under develop your film the highlight areas will be impossible to print correctly.

So increasing or decreasing the negative's development time does not affect the shadow density as much as it affects the highlights. So what does this mean; it means that by varying the amount of time you develop your film, you can produce a usable negative regardless of how contrasty or flat the subject may be.

So the general rules are as follows:

  1. Your exposure should be based on the amount of detail you want to have in the shadows/dark areas of your finished print.
  2. If your scene is very flat you can simply increase the negative's development time to make the high lights more dense. Which in turn will make the highlights on the print being whiter/brighter and less muddy. Some time referred to as N+.
  3. If your scene is extremely contrasty, you can compensate for this by giving the film less development. Some time referred to as N-.

A quick summary of this is, a longer devlopment increases the contrast and a shorter development time decreases the contrast.

Above I refer to N+ and N- what are these and what is N? Well N standards for Normal Development. Well for every film, developer and photographer there is a certain amount of development time that will produce a negative equal to the contrast to that of the scene. This is referred to as Normal Development denoted by the letter N.

Sunday, July 19, 2009

What is the Zone System

I eluded to the "Zone System" in my last blog. The Zone System was developed by Ansel Adams and Fred Archer as a simple and straightforward method by which they could control exposure.

Please note I am going to first talk about the Zone System from a photographic paper perspective and using B&W imagery. Later I will show how this can be used in all media types.

So what is this system and why did it come about. It came about because we see the world in a range of tones and brightness and darkness, and the humble light meter sees it as a uniform grey often refered to as 18% Grey. So to state the obvious it has something to do with exposure and the placing of them into zones. But what are these zones? A zone is the print value (tone) that will be produced when the image is properly exposed and developed for that zone . YOU determine the exposure, the exposure determines the Zone you get.

So how many zones are there? The Zone System assigns numbers from 0 through 10 to different brightness values, with 0 representing black, 5 middle gray, and 10 pure white; these values are known as zones. To make zones easily distinguishable from other quantities, Adams and Archer used Roman rather than Arabic numerals. So the mid tone 5 is known as Zone V. Each zone zone differs by a factor of two (2) so there is a one stop differance between each zone.

Since there are 11 zones, how many are actually use full to the photographer? The usefull ones are Zone I through Zone IX. These are the Zone I near black, with slight tonality but no texture and Zone IX slight tone without texture; i.e. glaring snow.

Zone 0 – the darkest possible black on the print
Zone I – the first tone above complete black
Zone II – the first signs of texture, slight detail
Zone III – dark areas with significant texture
Zone IV – dark foliage, etc in open shadow
Zone V – middle gray
Zone VI – Caucasian skin in sunlight
Zone VII – full textured highlights
Zone VIII – slight texture highlights
Zone IX – first tone darker than pure white on the print
Zone X – the brightest possible white on the print

Zones I – IX are considered the dynamic range (tones that will separate and have distinct tonalities between complete black and white)

Zones II – VIII are considered the textured range (tones that will show some or complete texture of the object)

It is worth noting, the number of zones you have available to you to use is dependant on the contrast ratio the print medium can handle. Photographic paper can do 100:1, dependant on quality of paper and type of processing. A computer printer’s tonal output depends on the number of inks used and the paper on which it is printed. So a good print is about 100:1. I know when you look at the image in print the tones are smooth and so it is difficult to see these ratios.

Thursday, July 16, 2009


Here is a quick outline of where I am going to take this blog for a while. I will be putting up and discussing my findings and feelings about digital metering and exposure.

I am of the school that was taught the "Zone System" of exposure for B&W photography. Spent my time running tests to calibrate film, processing methods, light meters and much more.

I have applied this method of exposure for both B&W as well as for colour film, both reversal and negative. And I know there is a whole school of photographers who will tell me this does not work.

What I am now trying to work on a method of digital metering and exposure as I am of the school that does not always trust my camera meter as I believe they measure 18% grey. Or should I say trying to fully understand how best to get the "correct" method of exposure and metering for digital imagery. Will this be using a spot meter or an incident meter. Sound very old school, yes it is, but I believe correct exposure for the image you are trying to create is very important.

Digital photography has a few other factors that one needs to understand and take care of, such as noise.