Close-up lenses (also called supplementary lenses
or Close-up filters) typically screw on the filter thread of the primary lens, and are manufactured and sold by suppliers of photographic filters. Some manufacturers refer to their close-up lenses as
diopters, after the unit of measurement of their optical power. screw into the filter mount on the front of
your camera lens. These lenses bring the focusing range of the
camera's lens closer to the camera. The power of close-up lenses is
normally specified in *dioptres; higher numbers are more powerful.
With the camera's lens focused on infinity and a +1 dioptre close-up
lens fitted, the maximum focusing distance becomes 1 metre, with a
+2 it becomes 0.5 metres, and with a +4 it becomes 0.25 metres.
Close-up lenses for 35 mm cameras
are commonly available with
strengths of +1, +2, +3 and +4, but intermediate and higher
strengths are also available. The lenses of digital cameras have
shorter focal lengths than those for 35 mm cameras, and so they need
stronger close-up lenses such as +7 and +10; these are often of too
small a diameter and insufficient quality to be used on 35 mm
Close-up lenses come in all normal filters sizes and can be used
with step-up rings so that you may use the same set of close-up
lenses on all your lenses.
Close-up lenses are not usually corrected for
aberrations, so you need to
stop down the camera lens to at least
f/8. The effects on image quality are greater with camera lenses of
longer focal length, so better quality (and much more expensive)
close-up lenses are needed for
telephoto lenses and for
cameras. Two-element achromatic close-up lenses are available: Nikon
produce +1.5 and +2.9, Canon produce +2 and +4, and Hoya produce
+10. Specially-matched close-up lenses are available for some macro
lenses and medical lenses.
You can use two close-up lenses at a time, with the stronger one
closer to the camera lens. The effect is additive, so a combination
of a +1 and a +2 has the same power as a +3 close-up lens. Combining
close-up lenses makes the drop in quality worse.
Close-up lenses are cheap, easy to use, cause no exposure
problems, and do not darken the viewfinder, but they cannot match
the quality of a macro lens. They are readily available, and are
made by camera manufacturers and by independent companies.
Extension Tubes vs Close-Up Filters vs Macro Lens
A close-up filter is an additional lens that attaches to the front of
your camera lens to allow it to focus close-up. Basically, it decreases the focusing distance allowing you to get closer to
your subject. Since they do not increase focal length there is no
light loss. Advantages are low cost and small size. Disadvantage is loss of optical quality. especially with the lens wide open, and around the edges. They can be used with
zooms, but the weaker
zooms perform better. The convenience they offer make them very attractive and useful.
Extension tubes extend the focal length of the lens, increasing magnification. Total extension/Focal length used = Magnification. The longer the focal length the more extension you need to make a significant
difference in magnification. Extension tubes use results in a loss of light. Most tubes, but not all, are meter coupled allowing your meter to work as normal. You need to check your cameras manual for
compatibility. Some will result in loss of
autofocus, which may not be that big a deal
with macro photography.
Kenko makes a great set of 3 tubes that can be used individually or separately
and will retain autofocus if you use AF for macro) and maintain the meter function so you still have regular ttl metering.
A true macro lens
is the best way to go. it comes ready made for close-up work without the need for supplements or extension.
You can also use tubes on them. The primary, if not the only, disadvantage is cost. But if you are truly interested in close-up photography, they are well worth the expense.
A second disadvantage would be the requirement to carry an extra lens, unless all you were doing is macro shots.
*Close-up lenses are often referred to as a "dioptre" - usage
akin to calling an electric heater a "watt" - a dioptre is actually
a unit for measuring the converging power of a lens. It's simply the
reciprocal of the focal length in metres, and since everything in
lens arithmetic works on reciprocals, this means that the powers of
two lenses can simply be added together.
An excellent book about close-up photography is John Shaw's Closeups in Nature (Practical Photography Books)
From Publishers Weekly
There's more than one way to shoot a frog, as Shaw demonstrates in this splendid book, a thorough course in practical field techniques for close-up photography using a 35mm single-lens reflex camera. Although hobbyists who want to capture the flowers in their garden can glean ideas for composition or the best time of day to photograph, this detailed work is intended primarily for the serious amateur or professional. Success in close-up photography, Shaw maintains, depends on control, and he advocates meticulous experimenting and testing of equipment and supplies before one attempts to
photograph in the quickly changing, unpredictable conditions of the field. Shaw (John Shaw's Nature Photography Field Guide) is an excellent teacher, establishing a common vocabulary with the reader, presenting lavishly illustrated new material that builds on previous knowledge, repeating important concepts and techniques for emphasis. He believes that technical competence frees the
photographer to concentrate on esthetics, and his inspiring pictures are beautiful artwork fields of flowers that evoke impressionist paintings, delicate dogwood blossoms reminiscent of Oriental designs, rare glimpses of snowflakes or raindrops on a yew needle. Photography Book Club main selection.
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