A CLOSE UP LENS screws to the front of the camera lens just like a screw filter. It allows the lens to focus closer than normal. They are available in a range of powers known as DIOPTRES.
HOW DO THEY WORK?
If you set the camera lens to infinity, a +1D lens allows focus to a maximum focus distance of 1 metre, +2D to 1/2m, +3D to 1/3m, +4D to 1/4m, +5D to 1/5m, +6D to 1/6m, and so on. They can be used together to form higher powers. A set of 3 close up lenses (usually +1D,+2D,+4D) gives combinations between +1D and +7D. To work out the magnification for any given set up, simply multiply the focal length of the camera lens (in metres) by the dioptre power of the close up lens. For a 50mm lens with a +4D close up lens, the magnification is 0.05 X 4 = 0.2 = 1:5. They do not have much effect with short focal length, close focusing lenses that are found with digital cameras especially those with macro settings. They are best used with longer focal length lenses.
WHAT DO I USE THEM FOR?
They can be used with all types of film and digital, compact and SLR cameras, as well as camcorders. They are ideal for copying old photographs, recording documents, photographing flowers, and small wildlife such as butterflies. They fit easily into the gadget bag or pocket. They can be used with most zoom lenses, although they may not be suitable at full telephoto settings.
The following examples were taken using a digital SLR with a 55-200mm lens
They work with fixed lenses and most zooms
For best results, do not use the zoom at maximum telephoto
55mm focal length - no CU lens 55mm focal length - CU+1D
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55mm focal length - CU+2D 55mm focal length - CU +3D (1+2)
55mm focal length - CU+4D
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200mm focal length - no CU lens 200mm focal length CU+1D
200mm focal length +2D 200mm focal length +3D (1+2)
200mm focal length +4D 200mm focal length +5D (1+4)
200mm focal length +6D (2+4) 200mm focal length +7D (1+2+4)
