Extension tubes a great way to focus much closer to small subjects such as an insect or flowers without the expense and weight of buying and carrying a macro lens. One extension tube takes up only as much room as a couple filters in a camera bag. Keep one or more in your camera bag at all times and you will always be ready for that macro shot.
The Kenko AF Extension Tube Set comes as a set of 3 tubes, a 12MM, 20MM and 36MM for Canon and Nikon DSLRS. The Kenko AF Extension Tube Set for Micro 4/3rds or Sony E-mount Mirrorless cameras come as a set of 2 tubes, a 10mm and a 16mm.
They are designed to enable a lens to focus closer than its normal set minimum focusing distance. Getting closer has the effect of magnifying your subject (making it appear larger in the viewfinder and in your pictures). Extension tubes are exceptionally useful for macro photography, enabling you to instantly convert almost any lens into a macro lens at a fraction of the cost while maintaining its original optical quality.
The DG extension tubes have no optics. They are mounted in between the camera body and lens to create more distance between the lens and digital sensor or film plane. Moving the lens father away from the camera’s sensor forces it to focus much closer than normal. The greater the length of the extension tube, the closer the lens can focus.
1) When an extension tube is used the lens focuses much closer than its normal close-focus distance. However, the lens focus range will be limited to a close focus distance while the extension tube is being used. During use the lens will not be able to focus to infinity. When you take the extension tube off and mount the lens back on the camera the lens will focus to infinity again.
2) As the focal length of the lens increases the effect of the extension tube decreases. A 20MM extension tube when used with a 50MM lens will allow it to focus incredibly close, maybe to just a couple inches from the subject. The same 20MM extension tube when used on a 200MM lens will only reduce the minimum focus distance by a small amount, maybe only a few inches closer than without it. To use extension tubes with telephoto lenses be prepared to use the 36MM tube or a combination of the tubes together.
3) There is effective light fall off as light travels the length of the tube. A 12MM extension tube has an effective 2/3 light reduction,. The 20MM extension tube has a 1 stop light reduction and the 36mm has a 2 stop light reduction. This reduction will be calculated by your camera’s meter automatically so if you are using automatic settings no adjustment are needed. Light metering will be accurate.
4) For best results, Kenko Tokina USA, Inc. recommends using a tripod for any macro photography.