AP explains… Affordable macro photography

  Mat Gallagher looks at how to achieve high - magnification macro shots using your current SLR kit and as little as ?4 worth of adapters COMPACT camera users don t often get the chance to scoff at their DSLR - wielding friends., but along with being able to slip the camera into their pocket, one such occasion is shooting macro images. Most compacts can simply switch into a  macro  mode, and while they canoffer full 1:1 magnification they can focus practically on the end of the lens. DSLR users looking to focus closer than around 30cm are asked to pay another ?300-?500 for a dedicated macro lens, but there are cheaper ways to get 1:1 magnification from your camera. Standard lenses are designed to focus to infinity and usually provide a close focus of around 1:10 magnification. However, by altering the light path, the focus can be shifted so that the lens no longer focuses to infinity and instead provides greater magnification. There are various ways to do this: aside from the popular use of extension tubes to physically distance the lens from the camera, high magnification can also be achieved by placing additional optics in front of the lens, mounting the lens the opposite way around or placing two lenses together using a reversing or coupling ring adapter. These solutions can provide much higher magnifications than a standard macro lens and can cost from as little as ?4 for the adapters.

COUPLING RINGS

The most impressive set-up is to couple two lenses together by attaching a long lens onto a camera as normal and then reverse - attaching a wider lens to the front via the filter threads. The required adapter, known as a coupling ring, costs from ?4-?30 and features two male filter threads for this purpose. They are usually the same size, but different combinations are available, as well as stepping rings for smaller or larger threads. The idea is to create a multi - optic macro arrangement, with the lens closest to the camera acting as an extension tube for the reversed lens in front. The magnification can be calculated by dividing the rear lens s focal length by the front focal length. So, a 200mm rear lens and 50mm reversed front lens achieve a 4:1 magnification, while equal focal lengths give a 1:1 magnification It is worth testing the lens combination before buying a coupling ring. To do so, hold the shorter lens against the front of the longer lens when attached to the camera. In many cases, the image will appear circular due to the front aperture being smaller than the angle of view from the telephoto lens, although dark corners can be cropped out if required.

MAGNIFICATION

Most standard lenses will offer around a 1:10 magnification when placed at their closest focus. However, by reversing the lens it is possible to achieve 1:1 magnification and beyond, depending on the focal length of the lens. For greater magnification, extension tubes or a longer lens can be put in between the reversed lens and the camera. A 300mm and a reversed 50mm provide 61 magnification

REVERSING RINGS

These adapters cost as little as ?10 and feature a lens mount on one side to attach it to the camera and a male lens thread on the other for fitting to the front of a lens. The lens can then be attached the opposite way around so the mount and contacts are at the front. By doing this, the light path is reversed and the focus point is more or less fixed. There will be slight movement when adjusting the focus ring, but the camera will have to be physically moved back and forth from the subject to find the point of focus. With no contact between the camera and lens, there will be no control of the aperture, so lenses with manual aperture rings are preferable. Lenses without aperture rings usually set themselves to their widest apertures when taken off the camera. This obviously results in a very shallow depth of field so these lenses are far from ideal. Remember, as the lens is attached by the filter thread, optics with other mounts can be used and stepping up or stepping down rings can be added to match the filter sizes of the reversing ring and lens. Place a back cap over the end of the lens when not in use, so that the rear element is not exposed to dust. The magnification available depends on the focal length of the lens - the wider the lens, the greater the magnification. A 50mm prime is ideal, or try a standard 18 - 55mm kit lens set to 18mm for extreme magnification. Extension tubes between the camera and the reversing ring can increase magnification further.

EXTENSION TUBES

Most photographers are familiar with this extension tubes, which fit between the camera and lens, shifting the local range away focusing to occur. Simple tubes can be picked up for as little as 30, although these offer no communication with the camera so focus must be I set manually and adjusted on the lens More advanced extension tubes, such as Kenko s Auto extension tubes, provide exposure and control, but cost considerably more, starting from around ?100. The optical arrangement of a lens is designed to work so that the distance between the rear element and the sensor is shorter than the front element and the subject When used with extension tubes, the distance from the back of the lens to the sensor is often greater than that from the front of the optic to the subject, so reversing the lens (using a ring) on the end of the extension tubes will allow the optics to be in the optimal arrangement.

CLOSE-UP LENSES

Close-up lenses attach to the front of an optic to allow it to focus closer. They come in differing strengths that can be applied individually for varying distances or combined for even higher magnification. Their effect depends on the focal length of the lens they are applied to, with longer lenses providing greater magnification. Close-up filters can also be attached to a dedicated macro lens. Single close-up lenses cost from 10-140, depending on the size of the filter thread, strength and brand. Sets can also be found from around 60.

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