Technique

 

Metering

This section is largely based on using the cameras TTL metering modes; it can be adapted to whatever metering mode you choose to use.

The camera meter will try to expose uniform grey card correctly, this is fine for mid-tone colours but for brighter or darker colours a little tweaking usually has to be done. I find that it is necessary to overexpose bright white subjects by about 1 - 1 1/3 stops, with a decreasing range for similarly bright colours. At the other end of the scale the opposite needs to be done, underexposing by a similar range for very dark subjects. This results in a better contrast between the colours in the final image. This assumes spot or partial metering of the subject or a subject that largely fills the frame.

As I have said elsewhere your camera may be able to take a bracket of photos of say -1 stop, -2/3 stop, -1/3 stop with just a single press which should enable you to cover any exposure problems. Without that facility you have to change the ISO setting on the camera for an ISO 50 film the following is a guide.

ISO Number

25

32

40

50

64

80

100

Exposure

+1

+2/3

+1/3

0

-1/3

-2/3

-1

  Light

Dark

I have this stuck on my camera together with depth of field guides and a checklist of things to make sure are set right before I start.

 

Flash

Flash can be extremely useful. It freezes the subject, as it has a very short burst time and can give a large depth of field when the natural light won't allow it, or a tripod is not feasible. It will allow hand-held photography at two times life-size with f16 apertures.

There are two distinct ways of using a flash. Firstly fill-in flash for when the ambient light is a little short of what you need, and a little burst of flash sorts out the problem. This is quite effective and leaves the background more or less intact. Metering for the background and then firing the flash, with a stop or so compensation gives a properly exposed subject.

A filled-in Giant owl - Caligo memnon.

If you need most of the light from a flash, for example indoors or for very small subjects then a slightly different technique applies. With a flash you can set the aperture and shot speed you want and the TTL metering system will sort out a correct exposure for the picture. Except of course the same rules for dark / light subjects apply. The flash has limits to its power though, this is given by its guide number. The rule is guide number over aperture equals effective shooting range, i.e. distance from the subject to the film plane. So for a macro-flash with guide number 11, you'll only be able to use it for f16 up to a range of 11/16m.(68cm)

The problems with the latter type of flash is that although the subject will be brilliantly sharp and properly exposed the background won't be, resulting in characteristic black areas in the back of the picture. If you can get your subject close to its background this problem can be minimised.

Heliconius hecale - Heceles longwing.

 
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All pictures in these pages copyright to Simon Coombes. Permission must be sought and obtained for any use.