Close-up photography - why is it so easy?

by Peter Rowlands

Reproduced from in focus 58 (September 1996)

Close-ups are by far the simplest and most effective form of underwater photography. As discussed in the article on basics, the three main variables you have to get right for a technically correct photograph are:

1. Focus.

2. Shutter speed.

3. Aperture.

Close-ups are so simple because, in most cases, you can preset and forget the first two of the these variables and the third doesn't have to be altered too much. If you've already got a TTL camera and flash system, you don't have to worry about the third!

Electronic flash is essential to restore the colour and detail in your subject and, in most situations, provides the total light for the exposure so no allowance needs to be made for available light.

For simplicity's sake, the flash position should be fixed to simplify exposures.

The first two 'variables' which can be preset are:

1. Shutter speed

The maximum shutter speed you can use is governed by the electronic flash and, on the Nikonos IVa and V, it is 1/90th sec but because the flash is providing all the light for the exposure, the shutter speed is almost irrelevant, even with cameras which can be used with a higher shutter speed.

Preset the shutter speed to the fastest setting your camera will allow for electronic flash and forget it. Using a slower shutter speed will make virtually no difference to the exposure.

2. Focus

With Nikonos close-up equipment such as close-up lenses or extension tubes, the focus is preset to make sure you are in focus where the frames indicate.

Altering the focus will in fact make little diflerence to the focus position but don't complicate things.

Preset the focus according to the manufacturer's instructions and forget it.

With reflex cameras you will be able to see the exact point of focus so you will not have to worry about correct focus.

3. Aperture

Because the flash is providing all the light for the exposure, the only variable to get right is the aperture.

If you are using a TTL camera and flash system such as the Nikonos V or Motormarine 11, the internal electronics will even adjust the light output for you -regardless of the aperture you use.

To understand the importance of selecting the right aperture let's assume we're using a manual flashgun so we have to set the aperture to get the right exposure.

When working at such small flash-to-subject distances, the guide number method (guide number/flash to subject distance _ aperture) of calculating the correct exposure basically still applies but in practice it's better to do a trial and error test.

This involves taking identical shots but varying the aperture from f2.8 down to f22.

The resulting slides will show the correct aperture for that type of subject. With close-ups, you won't need to go through the whole aperture range because the wider apertures will most certainly be overexposed so bracket your first shots from fl 1 to f22 to find the correct one for the tone of subject you are photographing.

The exact aperture will vary depending on the tone or reflectance of the subject so repeat this test on three subjects of differing reflectance such as a white sea urchin or starfish, a neutral tone subject such as a light green kelp and a dark subject such as a sea cucumber.

Having done this simple test, you are set up to take 36 out of 36 perfectly exposed frames per film and you only need to alter the aperture to take the reflectance of the subject into account.

Close-up equipment for non-reflex cameras

Two main devices enable the standard lens on a Nikonos or Motormarine II to focus closer than normal.

1. Close-up lenses

These optical devices are placed in front of the prime lens and enable them to focus closer - usually about 10 inches in front of the lens. They can be taken on and ofil underwater which gives useful versatility.

2. Extension tubes

These physical devices have no optics but just place the prime lens further away from the film. They are only available for Nikonos cameras. They must never be changed underwater.

In theory, the further away a lens is from the film, the more light will be needed to get the right exposure but, in practice, because the flash to subject distances get smaller the longer the extension tube you use, the effect is thankfully virtually counteractive.

Extension tubes bring you into focus much closer than close-up lenses.

Reproduction ratios

In order to quantify the performance of close-up devices (extension tubes in particular) the frame area covered is compared to the 35 mm film frame size.

A 1: 1 extension tube will take pictures of subjects the same size as the 35 mm frame, ie 24 x 36mm.

A 1:2 extension tube will take pictures of subjects four times the area of the 35 mm frame, ie 48 x 72mm.

A 1:3 extension tube will take pictures of subjects nine times the area of the 35 mm frame, ie 72 x 108mm.

A 2:1 extension tube will take pictures of subjects half the size of the 35 mm frame, ie 12 x 18mm.

Reflex viewing

For those underwater photographers who use a land camera in a housing (or a Nikonos RS) you will be able to have the versatility of a macro lens which lets you focus on anything from infinity down to around 6in from the lens.

The first two variables of shutter speed and focus are still not a problem but, since the flash to subject distances are going to vary considerably, so too will the aperture.

As before, if you're using a TTL system, the correct exposure will be sorted out for you by the system's electronics but, for manual exposure systems, you will have to set the correct aperture.

To simplify what can be a difficult area, it is best to mount the flash over the subject and forward of the camera so that the flash to subject distance doesn't vary much, even though the camera to subject distance varies considerably.

The big advantage of a reflex camera system is being able to see the exact point of focus through the lens as well as being able to frame the subject to your complete satisfaction.

Reproduced from in focus 58 (September 1996)