Set your camera to any of the auto or semi-auto modes. Photograph a dark tone (such as a black jacket), a mid-tone (the inside of a cereal packet traditionally makes a useful ‘grey card’) and a light tone (such as a sheet of white paper), making sure that the tone fills the viewfinder frame (it’s not necessary to focus). Add the shots to your learning log with quick sketches of the histograms and your observations.
You might be surprised to see that the histograms for each of the frames – black, grey and white – are the same. If there’s not much tonal variation within the frame you’ll see a narrow spike at the mid-tone; if there is tonal variation (such as detail) you’ll see a more gentle curve. If you find the tone curve isn’t centered on the mid-tone, make sure that you have your exposure compensation set to zero. You may see an unpleasant colour cast if you’re shooting under artificial light, in which case you can repeat the exercise using your monochrome setting (a light meter is sensitive to brightness, not to colour).
This simple exercise exposes the obvious flaw in calibrating the camera’s light meter to the mid-tone. The meter can’t know that a night scene is dark or a snow scene is light so it averages each exposure around the mid-tone and hopes for the best. But why can’t the camera just measure the light as it is? The reason is that a camera measures reflected light – the light reflected from the subject, not incident light – the light falling on the subject. To measure the incident light you’d have to walk over to the subject and hold an incident light meter (a hand-held meter) pointing back towards the camera, which isn’t always practical. If you did that each of the tones would be exposed correctly because the auto or semi-auto modes wouldn’t try to compensate for the specific brightness of the subject.
Set your camera to manual mode. Now you can see your light meter! The mid- tone exposure is indicated by the ‘0’ on the meter scale with darker or lighter exposures as – or + on either side. Repeat the exercise in manual mode, this time adjusting either your aperture or shutter to place the dark, mid and light tones at their correct positions on the histogram. The light and dark tones shouldn’t fall off either the left or right side of the graph. Add the shots to your learning log with sketches of their histograms and your observations.
Switching to manual mode disconnects the aperture, shutter and ISO so they’re no longer linked. Because they’re no longer reciprocal, you can make adjustments to any one of them without affecting the others.
Black Notebook –
Grey Hood –
White Paper –
With the mid-tone grey in the automatic selection, I see that because of the slight variant on the grey tone, there is more of a curve on the histogram, instead of a sharp spike. The slight curve indicated on the black is probably due to slight marks on the notebook cover that wasn’t visible to my eye and I can see that the white paper has a very sharp spike. Although all spikes remain in mid-tone area of the histograms for, without anything towards the sides.
I was surprised to see this result and the way the different tones has been represented by the automatic setting on the camera, but I do understand the concept and as to why; the camera is purely measuring the light reflected back to it from the object that I am photographing, thus resulting in these very similar pictures.
It shows us in some ways, that the camera is still not a machine that can do it all! We still need to exercise control over it in order to achieve the best results and it’s quite lucky in my opinion that we have the option to do this. By being able to manually adjust the settings as we need to, we can achieve our desired results, whatever they may be.
When taking the pictures in manual, it also showed me that you can’t always solely rely on your light meter if you don’t keep in mind exactly what it is showing. Of course, it gives us some ideas as to whether our picture is correctly exposed, but we still have to have some element of trial and error when taking photographs that are not completely planned from start to finish with the use of a hand held meter. I think that this is something that becomes more natural as time goes on and you take more pictures.
In the second set of pictures I can see that the histogram is where it should be for these ranges in tones, it is a good exercise to compare between the two.