P | P4 | Research

Light is measured by the camera’s light meter – but how does the camera translate this measurement into a usable exposure? In auto and semi-auto modes the light meter is calibrated to the mid-tone; this means that, after capture, the tone curve of the histogram will be centred around the middle of the graph. This works reasonably well if there’s an even spread of tones throughout the subject, but it doesn’t work so well if the subject is lighter or darker overall than the mid-tone.

If you’re not completely sure how your light meter works, try this exercise. 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 (you don’t have to focus). You might be surprised to see that the histograms for each of the frames are the same.If there’s not much tonal variation in your subject you’ll see a narrow spike at the mid-tone;if there is tonal variation such as detail you’ll get more of a gentle curve. If you find the tone curve isn’t centred 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 using your monochrome setting.

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 jacket is black or a sheet of paper is white so it averages each exposure around the mid-tone and hopes for the best.

If you’ve tried the exercise above why not include it as a post in the Research area of your blog rather than Coursework? Perhaps include an example of a complicated exposure (either your own or somebody else’s) which is not quite as you might expect, but the picture still works. An example of this is Rinko Kawauchi’s image for her photobook ‘Illuminations’, mentioned in Part Five.

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 above, this time adjusting using your 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.

Switching to manual mode disconnects the aperture and shutter 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.

Of course, you can adjust exposure in the other shooting modes using the exposure compensation button, but in manual mode you can keep one eye on the meter whilst adjusting aperture, shutter and ISO, giving you the confidence of being in complete control of the camera. Manual mode appears more complicated than semi-auto, but it’s actually more simple for situations where you have consistent lighting conditions. If you disconnect autofocus and shoot raw, manual mode represents an intuitive kind of photography that isn’t controlled inany way by the camera. As there’s no programming in the camera, you could say that the only programming to override is in the mind of the photographer. You’ll return to this point later in Part Four.

Auto

I tried to take a photo of a piece of paper however it only came out grey if I make sure the whole viewfinder is on the paper.

So I pressed on 'Adobe Adaptive' to see what happens to the image and if it turns more white, and it did. I also wanted to see what happens to the histogram when I do so and it moved more to the right.