Exposure Part V - Accurate Midpoints

In Part I of my guide to exposure I covered the basic technique of spotting on an object and adjusting for its colour.

You have to adjust for the colour because a spot meter measures the light reflecting off an object and the meter is calibrated to measure the reflection from a mid grey colour. Different colours require different adjustments.

I stated that green was pretty close to grey in that it made a good mid point. Generally this is right but, like many things, within reason. So, for example, a really dark green will need the exposure reducing a little and a really light green will need it increasing slightly.

9 times out of 10, I would look to get the exposure right to within a 1/3rd of a stop using this basic technique - using my experience of how to select and adjust a spot reading. And with practice, it can be done very quickly - even in rapidly changing light.

But how do you guarantee to get the exposure right?

Well for a sweeping vista there is not much more you can do. Your subject is in light that is too far away to do anything other than take a spot reading and use your judgment. But for scenes that are closer to hand, there are a couple of techniques you can use to nail the exposure.

The first involves exploiting the fact that the spot meter is calibrated for grey. If you place a ‘standard 18% grey card’ in the scene and spot meter off the card, the exposure will be accurate. Wedding photographers often use this technique. To be honest, I never bother because of the second option.

The second approach is to turn things around. Most handheld spot meters also have an incident light meter. This measures the light hitting the meter rather than the light reflecting off a subject. So, if you put the meter next to the subject, point it back at the camera and use an incident reading, you will get the exposure right. I used this technique on ‘Holding Out’ and I tend to use it for most inner landscape scenes where the light is not changing quickly.

So, over the last 5 articles, we have covered all the bases necessary to get the exposure spot on, time after time.

Most of these techniques are skills that are pretty easy to practice and turn into second nature. You need to be able to concentrate 100% on the creative part of making pictures when you are out in the field. With practice, selecting the best exposure (or indeed the exposure you want based on how you visualize the image) should be almost instinctive.

In the last part I bring the whole process together and examine the thought processes I went through in a number of real life, field situations.

© Jon Brock 2007