Get Closer; With The Right Lens Accessories; Extenders And Converters Expand The Limits Of Your Vision
I love getting intimately close to my subjects with my digital SLRs, especially nature, and to achieve this goal I’ll use the best tools at my disposal. Understanding that a macro zoom may not bring me as close as I’d like, I’ll turn to a macro lens. But even this lens may not be practical or readily available in all situations. Sometimes we’d simply like to extend the close-up capabilities of any lens currently in our camera bag, especially when traveling light—and to do so within our budget.
So what choices do we have in a reasonably priced accessory that will get us convincingly close without compromising image quality and with lenses we already own? From a practical standpoint, that leads us to extension tubes and even tele-converters (tele-extenders). And I found just the right ones: the Kenko Auto Extension Tube Set DG and Kenko PRO 300 Teleplus AF DG 1.4x and 2x
tele-converters. The “D” stands for “digital”; the “G” stands for “Gate Array IC.” That’s a fancy way of saying these accessories were designed around your digital hardware and that they maintain full microprocessor communication (auto-coupling) with the camera and lens. And that permits you to take advantage of autofocusing and autoexposure, while also maintaining full TTL flash control as well when using a dedicated shoe-mount. (Some caveats do apply, but none have affected my enjoyment of these accessories or their utility. Visit www.thkphoto.com for more info.)
What about plus diopters (close-up lenses) that mount onto the front of the lens, you ask? They’re an expedient choice. But you may need different size filters for different lens thread diameters (step-up/step-down rings are not always a practical solution). So this can become a costly prospect (especially for topnotch filters)—and a weighty one, when you add up all that glass.
How Do Extension Tubes & Tele-Converters Work?
How do extension tubes help to bring you closer to your subject? They increase the distance between the digital sensor/film plane and the lens. Extension tubes are typically hollow tubes of varying length (the Kenko DG series comes as a set of three tubes: 12mm, 20mm, and 36mm). The longer the tube, the closer it brings you to the subject with any given lens. Infinity focus is out of the question with an extension tube. If you want to retain infinity focus and still get closer, then a tele-converter may be the better choice.
Tele-converters go a step further. To increase focal length and thereby effectively magnify the image, they add glass, so the tube is not hollow. And as you’ll note in the Kenko DG converters, they’re highly corrected so as to focus the subject without any image deterioration. In the process, the converter retains the original minimum focusing distance, effectively enhancing the lens’ close-up capabilities.
Some people will also stack a converter with an extension tube or several extension tubes together, but that’s not something I’m keen to try. Why? If for no other reason than you lose light with any lens extension. A 1.4x and 2x converter respectively lose one and two stops of light. The loss of light with extension tubes can become dramatic when all three are stacked (a loss of two stops, as measured with this series). That may mandate stepping up to a higher ISO than planned or to use flash, especially when shooting handheld. And, of course, the closer you get, the more depth of field you lose, for any given lens focal length and aperture. However, thanks to auto-coupling, the camera reads that loss of light and responds accordingly.
Auto Drives The DG Series
The DG auto extension tubes can be used with virtually any lens (for that lens mount). But there is a practical limit to how wide you can go: it’s easy to get carried away and stick the lens right up against some protruding element by accident. Also, if you’re using a front-mounted macro flash, you might find the protruding flash limits how close you can actually get. That said, if you’re using a zoom lens, you’ll find that the shorter the focal length (within practical limits), the closer you can get—a good workaround to stacking extension tubes.
As for the DG tele-converters, Kenko recommends that they be used with fixed focal lengths not shorter than 100mm and zooms not shorter than 50mm. And, when used with autofocusing cameras, the converters are limited to lenses with a fast maximum aperture (f/4 or faster for a 1.4x and f/2.8 or faster for the 2x converter, owing to the reduced effective aperture, which may hinder autofocusing). Which makes my Tokina AT-X 535 PRO DX a perfect match for either converter, with its 50-135mm (= 75-202mm on a Nikon D300) zoom range and f/2.8 maximum aperture. As with the extension tubes, converters must be ordered for the correct camera lens mount.
The Kenko DG Experience
All in all, I’ve found my experiences with the Kenko DG lens accessories to be very rewarding.
I was able to take my zooms out and surprise even myself. Adding a 2x converter to that Tokina zoom, I shot a daffodil full frame with the camera’s built-in flash with no vignetting or loss in image quality.
And the coup de grace was a close-up of a wasp visiting a fresh tulip blossom, taken with the Tokina and 36mm extension. From a compositional standpoint, I couldn’t have done better with my macro lens! And, to top it off, this was a handheld shot made by available light.
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