Depth of field is a tool which may be used to great advantage in the creative aspects of underwater photography

Basic photography requires that you know how to deal with Depth of field (DOF).

This is a vital part of the composition and final appearance of your photograph, obviously because it governs how much of the image is in focus. It also has impact on other aspects of the image. The tips for taking digital photography should include a section on its ramifications.

HypselodorisApolegma  Nudibranch

The DOF is the area of your photograph which is in focus and sharp. These areas are said to be within the depth of field.
So in the photo above the DOF is quite shallow and ranges only to the immediate area of the nudibranch and surrounding coral in its immediate vicinity.

Depth of field (DOF) is directly controlled by the size of your aperture setting, the greater the aperture the lower the depth of field.

It is usually positioned with one third of the area in front of the focal point and two thirds behind. This means that when looking at your image, from the centre of the focal point, the area of the image which is sharp will be offset slightly so that the centre of the DOF will then be slightly behind the focal point – more sharp area behind the subject than in front.

When using compact digital cameras, by the nature of the camera and its tendency to operate in order to make photograph taking as simple and as easy as possible, your DOF will be greater as a default, usually minimum f-stop setting is f8.

You can decrease the DOF shooting with the lense zoomed out fully and getting as close to your subject as possible, this will result in more blurring of the background and therefore bringing ‘out’ the subject of your focus by defining it more.

Each f-stop change will give you a 40% greater or less depth of field – for example from f5.6 to f8 would increase your depth of field by 40% - so 40% more of the photograph will be in focus or sharp on the basis of the 1/3 and 2/3 ratio mentioned earlier. At f2.8 the background will be very blurred and at f22 the background would be quite sharp.

The ‘average’ f-stop to use is f8 and would be your default aperture when your DOF is not important to the composition of your photograph.

A problem which arises is the smaller the aperture the greater the diffraction of the light, so your photo will lose sharpness at higher magnifications.
This becomes obvious when you want to zoom in and crop a picture for example, you will find the fine detail of the subject is blurred at greater magnifications.

The closer you get to the subject the shallower the DOF both in front and behind, creating in some cases, an interesting effect on the photo, again enhancing the subject’s prominence in the picture.

Generally placing your point of focus one third of the way into your composition will ensure the DOF is balanced – refer to my earlier comment about one third of the depth of field being in the front of the subject of focus and two thirds behind.

More or less?

Christmas Tree Worms

When you have either a cluttered or distracting background, the DOF decreased to blur the background helps to draw the eye to the subject rather than being lost in amongst the background clutter in a photo with greater DOF. It may well have made the image above (at f16) a better photo.

Shooting at an aperture of less than f8 can sharpen the image so at a greater magnification the image detail will remain sharp rather than as mentioned earlier, the diffraction from the small aperture causing the image to lose sharpness.

Western Clown Anemone fish

As a whole using DOF to increase the blurring of the background can make the image ‘jump’ out. Almost making it three dimensional

Hairy Squat Lobster

In macro photography the DOF needs to be greater to avoid having important parts of the subject being blurred

Common Lionfish

When taking macro shots, having the camera set at a high f-stop like f22 creates the effect of a very black background as in the picture above.

Opening the aperture up increases the amount of light coming through the lense and so creates a more interesting background for the image, while still not a sharp and distracting background.

I hope this information fulfils expectations for beginning photography tips.

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