Review: Kenko Auto Extension Tube Set DG for Nikon

If you want to explore macro photography but don’t want to invest in a dedicated macro lens, for an investment of around $170.00, you can convert any lens into a macro lens.

Kenko, one of the THK group brands (Tokina/Hoya/Kenko) is well known for its auto extension tube set, available in Canon, Nikon and Sony/Minota mounts. Basically, it’s a set of three tubes, 12mm 20mm and 36mm in length, which are mounted between the lens and camera body, moving the rear of the lens further away from the film plane. The purpose of this is to shorten the minimum focus distance of the lens, which allows you to get closer to the subject, and thus increase magnification. The upside is that there are no optics to degrade the image quality. The downside is that you lose infinity focus.

The three tubes in the set can be used in any combination to give you different magnification factors. The longer the tube, the greater the magnification, but the narrower the range of distances at which you can focus. But what’s really great about this product is that it preserves all of the lens’ exposure and autofocus functions because each tube has a set of CPU contacts, an aperture lever, and a mechanical focus coupling. So, they’re compatible with both manual and autofocus/auto aperture lenses. The Nikon version tested here is compatible with all Nikon manual focus, AF and AF-S lenses.

The quality of the build is excellent, and they are quite durable despite their light weight, which is due not to quality, but to the absence of optics. There’s also a lot of rattling around due to the free-floating aperture levers, which goes away once a lens is mounted and it’s aperture lever spring takes up the slack. This may also lead to the misconception of substandard quality.

Focusing
Auto focus works well, making these tubes great for field work. However, used with slower lenses it can be tricky, especially when more than one extension tube is used. The extremely shallow depth of field wide open will cause the lens to hunt, and it may be difficult to direct the lens to what you are focusing on. But with practice, it’s possible to develop a technique that provides excellent results without the need for a tripod.

The more tubes you use, the narrower the range of focus, and you may find yourself moving in and out to help the lens find its mark. At this point, it may be easier to set the lens or camera to manual and focus by moving the camera in and out. Set the focus ring to infinity, and move closer to or farther away from the subject until you have focus confirmation. This is actually the traditional way of focusing in macro photography, and it works quite well. When using a tripod, a device exists for just this purpose—the macro focusing rail.

Exposure
Possibly the most important advantage is the preservation of TTL auto exposure. The added distance between the lens and film/sensor increases the necessary exposure, and the ability to meter through the lens and tubes and to use any of the auto exposure modes greatly simplifies things. This is especially true of cameras in which you cannot manually set the lens information such as the D90. It also enables TTL flash, which simplifies things even further.

Mounting
The extension tubes mount to the camera and to each other very easily, as do lenses to the tubes. The tolerances are not as great, so they go on very smoothly. You can feel the contacts engaging as you rotate the lens, which is a little disconcerting at first, but perfectly normal. The index markings (which are tiny red plastic inserts) make it easy to align to the camera and lenses). The release lever can easily be operated by the hand grasping the lens, while the other hand holds the camera body.

Reversing Lenses
In addition to mounting lenses conventionally, you can also reverse mount them to increase magnification. Using all three tubes with a reversed wide angle, such as the AF Nikkor 20mm f/2.8D creates an enormous amount of magnification. An object a quarter of an inch across will more than fill the frame. With this setup, you may lose metering and auto exposure capability, so you will have to rely on test shots and the histogram to arrive at the correct exposure. A tripod and focusing rail are recommended.

Using with Flash
Because the subject can be so close to the lens, lighting challenges can be overcome by using a macro flash such as the Sigma EM-140 DG. Keep in mind that the tubes achieve macro ability by reducing the focus distance, not by magnifying the image with optics. The more tubes you use, the shorter the focus distance and the harder it is to light. Therefore, extension tubes work best with longer lenses which already have greater magnification and long minimum focus distances. In some instances where multiple tubes are used, the focus distance may be shorter that the depth of the flash head, in which case the light from the flash will be blocked.

Using Zoom Lenses
Telephoto zoom lenses work better than standard zoom lenses. For example, the AF-S Nikkor 70-300mm f/4.5/5.6G works better than the AF-S DX Nikkor 16-85mm f/3.5/5.6G because most of the latter’s zoom range renders the working distance too short to be practical. Even with all three tubes, the 70-300mm’s working distance is still about 2", which works fine with the Sigma EM-140 DG. Zoom lenses bring the feel of working with a macro lens to extension tubes.

Using with Catadioptric Lenses
Let’s get ridiculous. When the 20mm tube is fitted to the Pheonix/Samyang 500mm f/8 mirror lens, something strange happens. Because this lens focuses past infinity (common for T-mount lenses to assure compatibility) it still makes infinity focus as a telephoto. However, no other combination of tubes allows this to happen. But with the other tubes, it certainly has the capability of focusing at about 30 to 50 feet, with enormous magnification. Used on a tripod or with a ring or conventional flash this lens could easily be used with or without these extension tubes as a macro lens due to its extreme close-focusing capability (5.5 ft @ 750mm!) So, it’s definitely worth pursuing.

Using with Canon or Other Brand Lenses
Because there’s no need to preserve infinity focus, you could easily use these tubes with other lenses with an adapter. In the case of a Canon FD to Nikon F adapter, you may be able to temporarily remove the optic, restoring its original optical quality. If you want to reverse the lens, you can then use the lens mount adapter in reverse to unlock the aperture lever.

Extension Tubes vs. Macro Lenses
It’s basically a matter of convenience. A macro lens is similar to a normal lens, except that it has a helicoid with a longer travel to allow for closer focusing. You determine the degree of magnification by moving in and out, and focus accordingly. The lens-to-subject distance can vary widely. With extension tubes, there’s a much narrower range of lens-to-subject distance, so the magnification is determined primarily by the length of tube you use, and there’s no longer the possibility of infinity focus.
With Zoom lenses, you regain the ability to adjust the scale of the composition by moving closer to or farther away from the subject. You just adjust the zoom to match the distance, and use the focus ring for fine tuning.

Recommended Lenses
Any lens with the equivalent focal length of 50mm or longer are suitable for use with extension tubes (this means that a 35mm lens can be used with an APS-C size sensor.) Less than 50mm, and the minimum focusing distance is already so close that the working distance may be impractical.

AF-S Nikkor 50mm f/1.4G
This lens is ideal under existing light conditions. Even with all three tubes used, there’s an adequate working distance to allow natural light to illuminate the subject. With fewer tubes, the quality of that light increases. The 75mm equivalent focal length help to achieve a higher magnification with a longer focal length.

Art glass vase. 20mm tube, about three inches across.

AF-S Nikkor 70-300mm f/4.5-5.6G VR
If you’re using a macro flash, this lens is wonderful. The longer minimum focus allows greater working distance, and the zoom capability lets you dial in your magnification. However, zoom works a little differently here; you “foot zoom” in and out to achieve the desired level of magnification, then use the zoom to bring the image into general focus, and fine tune with autofocus. Zooming essentially sets the “range of focus” for a given distance, as opposed to changing the actual scale. This makes a zoom lens behave more like a dedicated macro lens when used with extension tubes. Even with all three tubes used, under poor lighting conditions, auto focus at f/16 is possible.

Distressed face of an air velocity meter, about two inches across. 12, 20 and 36mm tubes used.

When the lighting conditions are adequate, existing light can also be used, although a larger aperture may be required, thus narrowing the depth of field. Plus, it may require a shutter speed that eliminates the possibility of hand-held use, but the VR helps out greatly in this regard.

AF Nikkor 20mm f/2.8 (reversed)
When reversed and used with extension tubes, this lens provides a fast and compact solution for photomicrography, it’s that powerful. Manual focus and aperture make it best suited for studio work.

The first three digits of an 1899 penny. Only the 20mm tube was used.

Phoenix/Samyang 500mm f/8.0 Mirror Lens
As crazy as this seems, this lens does macro. With a minimum focus distance of 1.72m (5.5') @ 750mm (APS-C), this lens lens can do extreme close ups. But, when combined with a standard (not macro) flash and all three extension tubes, it can do this:

Lucky Penny from four feet; 12, 20 and 36mm tubes, Nikon SB-900 speedlight @ 200mm zoom.

Granted, this was helped along a little with post-processing. But it’s possible to make this shot hand held, with manual focus, exposure and flash. The flash is what makes this possible. With the zoom head of the SB-900 set to 200mm there’s plenty of light on the subject, and the flash is so easy to set up manually that it’s a breeze. Focusing was achieved by setting the lens to its minimum focus, and moving the camera in and out slightly until sharp.

Sextant at twenty-five feet. 12, 20 and 36mm tubes, ISO 400,  Nikon SB-900, 200mm zoom.

The focus range is so wide that even with all three tubes you can shoot from about 4 ft. to 30 ft. You just compose, turn the focus ring until sharp, then move the camera in and out very slightly to fine tune the focus. As soon as it’s sharp, trip the shutter. Don’t worry about camera movement, because it’s cancelled out by the flash.

Voigtländer Ultron 40mm f2.0 SL II (normal or reversed)
If this were a contest, the Voigtländer just might be the winner. It works equally well normal or reversed, and with its ability to use all three tubes in either configuration, it has the widest range of scale. It’s fast and tack sharp.

Christmas Bulb Filament. Reversed with 12, 20 and 36mm tubes, Sigma EM-140 DG flash. All manual.

1899 Penny. Normal, 12, 20 and 36mm tubes, Sigma EM-140 DG flash (TTL). Manual Focus. 

Build Quality ★★★★★

High quality plastic with metal mounts and other components. Pristine fit and finish.

Compatibility ★★★★★

Works with with manual focus, AF or AF-S lenses.

Optical Quality ★★★★★

No optical elements mean no degradation in image quality. Period.

Value ★★★★★

This set can turn so many lenses into macro lenses, You’ll spend more time having fun than thinking about the money you saved on a dedicated macro lens.

Specifications

You can view Kenko’s Specifications for this product by visiting their website.

Highly Recommended!