Extension tubes are intended to empower a lens to focus nearer than its ordinary set minimum focusing distance. Getting nearer has the impact of magnifying your subject (making it seem bigger in the viewfinder and in your photos). They are extraordinarily helpful for macro photography, empowering you to convert over any lens into a macro lens at a small amount of the expense while keeping up its original optical quality. The extension tubes contain no optics. They are mounted in the middle of the camera body and lens to provide more distance in between the lens and film plane. By pushing the focal point more distant away from the CCD sensor or film in the camera, the lens is compelled to focus much nearer than normal. The more the length of the extension tube, the nearer the lens can focus.
Extension tubes extend the lens focal length, increasing magnification. total extension/Focal length utilized = Magnification. The more focal length the longer extension you need to have a noteworthy effect in magnification. Extension tubes use results in lost light. Most tubes, yet not all, are meter coupled permitting your meter to work normal. You should check your cameras manual for compatibility. Some may result loss of autofocus, which may not be that huge a deal with macro photography.
Extension tubes are different from extenders (additionally called Teleconverters). Extenders are for shooting objects a long distance away and making them appear nearer. Extension tubes are about permitting lenses to get physically nearer to your subject by decreasing the minimum focusing distance. They go between the lens and the body exactly like an extender yet have one significance difference - Extension tubes are only a tube - they contain no optics in them.... therefore you finger can go directly through from one side to the other on the off chance that you put it in the hole. The amount that they permit you to get nearer and the increased magnification on the subject as a consequence of that is represented by the focal length provided by the lens and how near the lens will focus by itself. Extension tubes can be added to any lens. There is a little light loss yet with lenses more than 50mm this is negligible. These are not normally utilized with wide angle lenses as the to the extremely close focusing distance they give makes it unfeasible to use.
Without electrical contacts
Extension tubes without electrical contacts won't permit an electronic programmed camera to control the lens, therefore disabling autofocus and sometimes forcing a user to shoot completely open unless the lens has manual aperture control. More expensive tubes contain electrical contacts permitting the user to utilize autofocus and control the aperture of the attached lens electronically. A great advantage of the non-electrical tubes is their low cost. Since no electronics or optics is included, it is typical to discover low cost rings.
With electrical contacts
The SET of KENKO AUTO EXTENSION TUBE feature three tubes of various lengths, a 12 mm, 20 mm, and 36 mm, and may be utilized individually or in any combination to acquire the desired magnification. Kenko additionally makes a UNITUBE available in 12 mm or 25 mm which may be purchased separately.
Kenko's Auto Focus extension tubes are engineered with all the electrical circuitry and mechanical coupling to maintain autofocus and TTL auto exposure with most Nikon lenses provided there is sufficient light to properly activate the cameras AF.
KENKO UNIPLUS TUBE (extention ring) is an accessory only intended for use with standard AF lenses to shoot objects at nearer distances with higher magnification. The magnification ratio for TUBE 25 is around 1/2 when used with 50mm standard lenses providing perfect coupling featuring automatic aperture, TTL metering and AE device.
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Extension Tubes vs Close-Up Filters vs Macro Lens
A close-up filteris 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.