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!)
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.
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.
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.
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!
Often thought of as an antiquated method used by old men with long beards to calculate their exposures for their funny looking view cameras, the zone system is actually as important today as it has ever been! The zone system offers us a pathway to achieving our desired look in an image in a deliberate way. As I’ve mentioned before, I am a big fan of any photography method that forces us to work in a deliberate fashion.
The Zone system is divided into 11 tonalities that generally speaking are separated from each other by 1 stop of exposure. Zone 0 is pure black, Zone V is 18% grey and Zone X is pure white. These three zones are reference points, and the remaining 8 zones provide the gradations in tonality
Let’s do a very basic, short exercise to see how our own cameras relate to the zone system. Place your camera on a tripod facing a relatively evenly lit white wall. Set your camera to record in B&W JPEG mode at the base ISO, set the meter to spot mode and make sure the exposure compensation is set to Zero. It might be helpful to manually focus to infinity as the lack of detail on the white wall may confuse your cameras autofocus system. Now take one image, compare it to the Zone V tone in the step diagram in this article, you will probably find it to be almost identical. This is because our camera’s meter is calibrated to Zone V.
Starting at your Zone V reference point, take 5 photographs increasing the exposure by one stop with each capture, then return to Zone V again and do the same, but decrease the exposure by one stop for each frame. The result is 11 images that will closely resemble the step chart. Note not all cameras record a full 11 zones, particularly in JPEG mode, so for example if you don’t see any difference between Zone IX and Zone X, then your camera in JPEG mode is achieving Zone X with +4 stops of exposure compensation. Conversely you will probably be able to see small changes in tonality all the way down to Zone 0 with most digital cameras, and in some cases even down to Zone -I. Digital cameras record and recover shadow detail far more easily than film cameras, however film cameras can often record highlights far beyond what is achievable with digital. The end result is they both have a similar dynamic range, but a different look. But that’s a discussion for a different day!
If we go back to our first example (Fig. 1) in this scene and compare the image to our little step chart depicting the Zone system, we can see that the majority of tones in the image are between Zone II and Zone VIII. This is generally the useful range of tone for an evenly exposed photograph. Further more, the tones where meaningful texture is visible is between Zones III and Zone VII.
So how do we use this exercise to solve practical problems whilst out photographing. Let’s take an example of a snow covered landscape on a bright sunny day. From our Zone system test we saw that the camera may record bright white light as middle grey. If we want to record our snowy scene as white, with textured snow for example, we may find it helpful to set our camera to +2 stops exposure compensation placing the snow at Zone VII. If you do this also have a look at your histogram to make sure that the highlights are not getting blown out. The significance of this is that we have deliberately decided the tonality of our scene!
If you are photographing a black car for instance, your meter might try to over expose, because it is trying to make the black car look middle grey. In this case, find a shadow area on the car that you want to still retain some detail and texture, take a meter reading and set your exposure to be -2 stops. For instance if you metered the cars tires, and found them to give you a reading of 1/125 and f/5.6… set your camera to expose at 1/125 and f/11. The result should be a correctly toned, black car!
These are generalisations of course, nothing can replace good experience and experimentation! But I hope this exercise helps demonstrate how combining the best features of our modern histogram, and the older zone system can be used to control an exposure in such a way that the results resembles your intended vision!
Good luck and happy shooting!!