What is macro?
True Macro, is photography at 1:1 magnification and greater. Anything less would be defined as “close-ups” rather than “macro” but for now the term macro will also include close-ups which are not quite 1:1 (or life size).
There are quite a few different ways and methods of acheiving this which involve different equipment, at varying prices. But first you should ensure that you are familiar with the close-up possibilities of your camera and its existing lenses. When you feel that you need to go beyond these capabilities then you should read on.
Dioptres or close-up lenses are simply magnifying glasses that you can screw onto the front of a lens to increase object size. Whilst the quality of a close-up lens may be good it will not match a dedicated macro lens but they are excellent if your budget is tight or space and weight is at a premium when travelling. If you are using a small aperture then you are only using the centre part of the close-up lens which will improve your chances of getting a good result. Close up lenses come individually or in sets and are defined by their dioptre value so 1, 2, 4 and 10 dioptre are common examples.
Extension tubes offer an alternative at a reasonable cost. In theory to gain 1:1 magnification you need the same number of mm of extension as the lens you are using, e.g. a 50mm lens would need 50mm of extension. Unfortunately, it isn’t as simple as just using a 24mm wide-angle lens with a 24mm extension tube to achieve 1:1 either, since your working distance may be virtually non-existent or actually inside the lens itself.
You can reverse either a kit lens or say a 50mm lens directly onto the body using a reverse body coupler. This suffers from the problem of losing aperture control as there is no electrical connection. You can get round this problem by using a reversed older manual lens which has an aperture control ring. Normally when using a lens on your camera the viewfinder is bright only stopping down to your selected aperture whilst you depress the shutter button, when reversing a lens the aperture is set first resulting in a dimmer viewfinder.
Another reversing technique is to reverse lens onto the front of another lens. For this you need a male/male lens reversing coupler that has filter threads fitting both lenses. This has one advantage over the previous reversing method in that you retain aperture control of the main lens. This is normally done with a smaller focal length lens reversed onto a longer lens. With a 50mm lens on the front of a 100mm macro lens you will get approx 3:1 magnification.
Dedicated macro lens
True 1:1 lenses come in varying focal lengths. The longer the lens the greater the working distance (ie between front of lens and subject, which is useful for insects etc). As a guide here are some typical working distances : 50mm 1.6 inches ;105mm 4.7 inches ;180mm 9.1 inches . Good macro lenses can be expensive. You can increase the magnification further by adding extension tubes, with a 1:1 macro lens of 150mm focal length or less you can get to 2:1 magnification or higher using a full set of extension tubes ( for example 68mm)
Depth of Field (DOF)
DOF in macro photography is usually very limited, the increased magnification you get with macro comes at the expense of depth-of-field. Depth-of-field is how much of the picture is in sharp focus. There is an inverse relationship between magnification and DOF, the more magnification you get, the less DOF you get.
To achieve greater depth of field there are numerous versions of focus stacking software available, this is where you take a number of shots varying the part in focus and use software to combine these. This however is a specialist field in itself.
Natural light is fine for macro shooting upto 1:1 magnification but past this becomes increasingly difficult. Using flash gets enough light with small the aperture values that are often used to get reasonable DOF. It becomes a necessity for most shooting above 1:1 simply because there is not normally enough light. There are also several LED lights available which can be used for macro photography. These have the added advantage of being able to judge the effect of the lighting before taking the picture.