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Zoning in for perfect Exposures



So after reading our last 2 blogs you have become motivated to try Black and White photography! Great! But the moment you turn your camera in to monochrome B&W mode you are presented with murky, uninspiring shades of grey that left you dreaming about the lively colours you just left behind!?


It’s time to talk about using histograms and the Zone System to bring out the drama of Black and White photography!

That Jagged Mountain Graph (AKA the histogram!)


Hand drawn example of a histogram

The histogram is nothing more than a graphical representation of where the tones in your image are. Have a look at the above drawing of a histogram. It is defined by a shadow limit on the left side of the graph, this represents the black point of the image, beyond that tones can get no darker. On the right hand side the histogram is defined by the white point, if pixels in our exposure exceed the white point they become pure white and contain no information.


The ideal exposure would have tonal values just starting at the black point and building gradually towards the mid point then reducing down to almost zero just before the white point! I have provided some examples in this article with their histograms and a step chart representing the Zone System which we will be talking about later in this article.


The ideal image with regards to histograms seldom exists in the real world, but the first image in Fig. 1 of our examples demonstrates the concept nicely. The Histogram is in the top right corner.


An evenly exposed B&W photograph with a good range of tones
Fig. 1: Evenly exposed scene

In most cases achieving an evenly exposed image like this will give a great result. That being said, if we want to add drama, or communicate a certain mood we need to look at ways to go beyond the "ideal" image and histogram.


In this next example (Fig. 2) we are looking at a high key image, along with its corresponding histogram, notice how the majority of the histogram is heavily weighted to the right hand side, and more importantly see how the tones of the image are all rather light? This was intentional as I felt a high key image communicated the elegance of this building in a beautiful way. The surface of the building is bright, but still retains detail throughout, and the sky is not blown out, retaining just the last bit of tonality in the highlights.


Fig 2: High Key

In this third example (Fig. 3) the low key tones on the facade of the building give a dramatic, mysterious feel. The histogram is heavily stacked to the left! Metallic surfaces can render wonderful tones! In this case the light was catching the corner of the building resulting in these nice gradations.


Fig 3: Low Key

These are fairly simple examples that demonstrate what the histogram is telling us. Controlling the histogram is a simple matter of adjusting exposure. In automatic, or semi-automatic modes we can do this by applying exposure compensation. For example, if the histogram is stacked up against the right hand side, and the highlights are blowing out we can decrease exposure by selecting a negative exposure compensation that keeps the exposure within the highlight range. If we are finding that the image is clipping the shadow side of the histogram we can increase exposure by selecting a positive exposure compensation. In manual mode we can adjust either aperture, shutter speed or ISO (on digital) to achieve the same result.


Achieve your specific vision with the Zone system


So this all seems fairly straightforward, most of you have probably read about it before. Histograms do a good job of telling us about the range of tones we have captured, however it doesn’t tell us if the tones of a specific area relate accurately to the way we intended them to look. For this we may find the Zone system to be an indispensable tool!