Shooting at the Shallow End
Using Shallow Depth of Field in your underwater shots.

I guess we first need to define what the term “Depth of Field” actually means.Also we can use this opportunity to introduce the shorter three letter term we generally use instead of the usual words
and that’s “DoF”

DoF is a very simple thing and it’s the area in front of and behind what we are focused upon that is also seen to be in focus.
If we were being really pedantic there would only be one finite point that should ever be considered in focus, however normal human eyesight will assume that there is an area that is deemed sharp enough, and that area is our DoF.
Without this becoming too much of a physics lesson, the DoF is influenced by a number of factors, but the main ones that we are concerned about here, are the distance from the subject, and the aperture we choose to shoot at.
The closer we get to the subject our DoF reduces, and also the wider our aperture chosen and our DoF reduces.
Traditionally for UW macro photographers demanding the maximum amount of sharpness in their shots of some of the reefs tiniest creatures, the very smallest apertures have been chosen to maximise the DoF.
For those photographers though wanting to move away from the norm, and try something different, then eschewing tradition and choosing the much wider apertures       ( or smaller numbers ie f2.8 f3.5 etc) that lenses have, will give you some further more stylised options to portray  the underwater world.

Our title slide is an example of this, I was backlighting this Chromodoris but only wanted to highlight the leading rhinopore on this nudibranchs head, now of course there is a choice here, I could have shot a more fish ID style pic and tried to get more of the slug in focus, but I wanted to only have the ridges on the horn to be the only thing in focus, so I shot at f3.5 in this particular case. There is an element of chance in all this, so it’s worth taking a few shots to make sure you get things as you wish. It won’t always work and there is a much less of a margin for focussing error.

 

 

A shot of a chromodoris where only the leading horn of the backlit nudibranch is the bit in focus.

A shot of a chromodoris at the maximum aperture of f2.8 where only the leading horn of the backlit nudibranch is the bit in focus.

 

 

There are some issues that need to be considered though.
Firstly shooting at the wider apertures will mean that in bright ambient light conditions then you may well find that you run the risk of over exposure, particularly if using a strobe, and your flash synchronisation speed is lower than a 1/200 sec.
Try shooting using available light in this scenario, but be careful about camera shake, as the high magnifications involved in macro photography will exacerbate any tiny movements introduced by you.
Another big problem you will encounter is that your success rate for shots with the all important “eye-focus” will plummet.
With such shallow DoF then the fraction of time between taking the shot and the camera acquiring focus, can be enough for you to move a tiny amount, and we are talking as little as a millimetre sometimes at the very widest apertures.
You will also have to make judgement calls based upon what in the photograph is the primary object you need in focus.
These types of shot will often result in only one element of the photograph being in focus, which can cause something of a compositional conundrum, so you may well find yourself taking lots
of pictures so that you can choose your favourite later.
Checking focus on the screen after you’ve shot is vital, zooming into the picture to check that the part of your picture you want in focus is actually in focus. It’s easy to get this wrong, so check and check again.

 

Here because of the very shallow DoF the only eye that is in focus is the one closest to the camera.

Here because of the very shallow DoF the only eye that is in focus is the one closest to the camera.

Of course this technique can be used in conjunction with other techniques, as can most of your underwater photography skills. Mixing things up a bit will help you learn to adapt to different circumstances and subjects to expand your creative horizons.

Practice this technique with familiar subjects, I have chosen a Lizard Fish here as it is an easy shot to get head on, using this shallow DoF technique helps to concentrate the attention on the eyes and the inherent character of the creature. It also allows you to blur out a boring and distracting background.

 

Shooting at an aperture of f2.8 has allowed me to completely blur out the fore and background. Allowing the eye to home in on the creatures head.

Shooting at an aperture of f2.8 has allowed me to completely blur out the fore and background. Allowing the eye to home in on the creatures head.

 

I’ve shot this small fish living in the neck of a long discarded bottle to show its home, I had to be careful with my timing to make sure I waited for the fish to be directly in line with the rim, so that the eyes were nice and sharp.

 

A small fish living in a bottle had to be carefully shot so that it was in line with the rim which I wanted to be sharp, to show what it's home was.

A small fish living in a bottle had to be carefully shot so that it was in line with the rim which I wanted to be sharp, to show what it’s home was.

 

 

Adding this technique to your repertoire will give you a valuable skill, that you can employ for abstract and artistic reasons or simply to help get rid of distracting and ugly backgrounds. It is trickier and you will have much less of a successful hit rate than if you were shooting at more regular smaller macro apertures so why not practice out in the garden at home with insects and plants.