How to choose and use teleconverters

Left Image: Minolta Maxxum 7, 300mm f-2.8 APO lens, 2X APO teleconverter, Bogen tripod and ball head.
Spot metering (condor's face) on aperture priority, +1/2 exposure compensation, approx. 1/30 sec at f-5.6, autofocus.

Teleconverters have come a long way. They are no longer cheap low quality accessories they once were. Quality teleconverters are now made by camera and lens manufacturers at affordable prices. There are mainly two types of teleconverters available: 1.4X and 2X power. Kenko makes (or made) a 1.5X power teleconverter as well as a 3X Pro.

As I mentioned on some of my other articles about teleconverters, you can increase your lens' focal length by 1.4X or 2X while loosing one or two stops of light. Your 300mm f-2.8 lens becomes 420mm f-4 with a 1.4X teleconverter and 600mm f-5.6 with a 2X teleconverter attached. There are definite drawbacks to teleconverters. One drawback is what I just mentioned. Loss of one or two stops of light. The other is loss of image quality, especially at wide open apertures.

 The advantage of having teleconverters, is being able to increase your lens focal length with small accessories that will fit even inside your shirt pocket. You also maintain minimum focusing distance. A 300mm f-2.8 lens that can focus to 6 feet, becomes a 600mm f-5.6 with the same 6 foot close-focusing capability. There are two types of 1.4X and 2X teleconverters available: Dedicated and generic version. Lets start by looking at the dedicated models first.


Dedicated teleconverters work only with certain camera manufacturers own lenses. Canon, Nikon, and Konica Minolta versions for instance, work with fixed focal length, fast aperture telephoto lenses, although Canon and Nikon 80-200mm f-2.8 zooms can also be used with their 1.4X and 2X teleconverters. Dedicated teleconverters cannot be attached to other lenses. These models are expensive, costing 300 to 400 dollars. The quality however, is well worth the money. If you own a 300mm f-2.8 and you feel you need longer lenses, a 400mm f-2.8 will cost you $7000 and a 600mm f-4 another $10,000. A pair of dedicated 1.4X and 2X teleconverters give you a 420mm f-4 and 600mm f-5.6 for under a thousand dollars. You still get the magnification you need and 420mm f-4 and 600mm f-5.6 lenses are fast enough for focusing and shooting. Carrying a 300mm f-2.8, 400mm f-2.8, and 600mm f-4 will require a mule, but a pair of teleconverters will fit nicely inside your camera bag or photo vest.

 

Canon EF 1.4x dedicated teleconverter

Kenko 1.4x non-dedicated teleconverter

Both 300mm f-2.8 and 400mm f-2.8 lenses work beautifully with teleconverters. Even with a 2X teleconverter, you get f-5.6 maximum aperture and 600mm or 800mm super telephotos. Avoid using 2X teleconverters with lenses having the maximum aperture of f-5.6 or smaller. Even lenses with f-4 maximum apertures may be difficult to handle with 2X teleconverters. A 300mm f-4 with 1.4X teleconverter becomes a 420mm f-5.6. You can get high shutter speeds at f-5.6 and still maintain quality. At f-8, that is a 300mm f-4 with 2X teleconverter attached, autofocus with most cameras won't work and shutter speed will drop by one full stop. This may not sound too bad, but in reality it is a big difference. With long lenses, we need all the speed we can get to freeze movement and reduce camera vibration. A 600mm lens requires very fast shutter speeds for moving wildlife or sports photography. With an ISO 100 film at f-5.6 your shutter speed will be 1/1000 sec under bright sun for a middletone frontlit subjects. This is excellent. Even f-8 will give you 1/500 sec shutter speed. The problem is that we rarely shoot under ideal situation. I consider myself lucky when I can use 1/250 sec at f-2.8 with my 300mm lens.


The problem becomes worse with 400mm f-5.6 lenses and teleconverters. Canon's EF 400mm f/5.6L USM for instance, is a superb lens and can be attached to EOS 1.4X and 2X converters. The problem is, 560mm f-8 and 800mm f-11 are slow for most moving subjects, and we usually use longer lenses for wildlife or sports photography. Konica Minolta Maxxum 400mm f/4.5 APO G is half stop faster than Canon's version. Still f-6.3 and f-9 are slow apertures. Use these lenses by themselves or a 1.4X teleconverters only if you absolutely have to and know your shutter speed will be high enough.



Left Image: Konica Minolta 300mm f-2.8 APO with dedicated 2x teleconverter


Longer than 400mm lenses can also be used with teleconverters. Avoid 2X teleconverters and stay with 1.4X version. 500mm f-4 or 600mm f-4 telephotos become 1000mm f-8 and 1200mm f-8 lenses with 2X teleconverters. This is a lot of power and very difficult lenses to handle in the field. You'll require two tripods, one under the lens and another under the camera to keep everything steady. f-8 at these magnifications is also slow.

Loss of quality should be expected even with dedicated lens and teleconverters. It depends on the combination. For example, my 200mm f/2.8 APO and 1.4X teleconverter produce almost no visible loss of sharpness and only some loss of corner sharpness with 2X teleconverter. The same teleconverters with my 300mm f/2.8 APO shows slight softness around the edges with 1.4X but more with 2X teleconverter. You can stop the lens down to improve center and corner sharpness, but as I mentioned before, this is not always possible due to low shutter speeds. If you own or plan on buying faster telephoto lenses, buy dedicated teleconverters for best results.


Sigma, Tamron, and Kenko generic teleconverters can be attached to almost any lens. 1.4X and 2X teleconverters made by these companies are more affordable than dedicated cameras brands. The quality has improved in the past few years. Lets see which combinations work best.


First of all, zooms don't work well with teleconverters, especially those with f-5.6 maximum apertures. Lets say you own a 75-300mm f-5.6 zoom. Adding a 2X teleconverter gives you 150-600mm f-11 zoom. There will be loss of image quality due to the lens/teleconverter combination. You must stop the lens down one or two stops to improve sharpness. You end up at f-16 or f-22. Even f-11 is slow for shooting even under best of conditions. You could get some acceptable results with 1.4X teleconverter attached to a 75-300mm f-5.6 or 100-400mm f-5.6 zooms. I tell you right here, you have to experiment for yourself. I have used a few zooms with teleconverters, and can tell you the final results were poor to acceptable. It depends on the zoom and teleconverter. A fast 80-200mm f-2.8 can be used with both 1.4x and 2x teleconverters with good results and decent maximum apertures. I can't say which brand zoom and teleconverter work best, because I haven't used all models. If you want to use this combination, stay with the same brand. Use Sigma 70-200mm f2.8 with Sigma teleconverters or Tokina 80-200mm f/2.8 with Kenko (Tokina and Kenko are part of the same company) teleconverters. Lenses and teleconverters made by the same company have same type of glass and coating.


Another alternative is Sigma 100-300mm f-4 zoom. This lens is an excellent zoom lens. If you can't spend on more expensive fast telephotos and don't mind some loss of quality with zooms and teleconverters, you may want to try this zoom. Stay with 1.4X teleconverters. You get an extra 120mm of focal length and loose only one stop of light. For non moving subjects, you can also try the 2X teleconverter. You can stop down one or two stops to improve overall sharpness. One other affordable combination is the Sigma or Tokina 300mm f-4 and 1.4X teleconverter. Quality of the prime lens and teleconverter is very good. You can use the 300mm f-4 with 2X teleconverters with good results under bright sun or for less active wildlife.

 
Once you find the perfect lens/teleconverter combination, you need to use them properly. One thing many people forget, is the combination results in a longer lens. Start with a 300mm f-4 and you may be able to handhold the camera. Add a 2X teleconverter and you get a 600mm f-8 lens. A tripod is definitely needed. Even smaller and lighter zooms will require a solid support. Lets say you add a 2X teleconverter to your 75-300mm f-5.6 zoom. At f-11 things look very dim to begin with. Zoom out and you have a very slow 600mm lens. Camera vibration, subject movement, and slow shutter speed will result in blurry images unless you use a solid tripod and cable release. Get as close as possible to your subject. Use the longest and fastest lens you own before attaching teleconverters. Attach your teleconverter only if you have to. Try the 1.4X first. You loose only one stop of light and maintain better quality. Use your 2X teleconverter if getting closer is impossible and you feel you can maintain high enough shutter speed. If possible, stop down one or two stops to improve corner sharpness. This is of course, not always possible.


You can use teleconverters for close-up photography as well. If your zoom can focus down to 1/8 life-size, with a 2X teleconverter you get 1/4 life-size. If you own macro lenses, you can double the magnification by using a 2X teleconverter. Your 50mm f-2.8 macro with life-size capability becomes a 100mm f-5.6 with twice life-size magnification. The difference is a full size butterfly at life-size or the butterfly's portrait at twice life-size. The good thing about teleconverters for close-up photography is that loss of image quality is not a major factor since we almost always shoot at very small apertures to gain depth-of-field.


Left image: Konica Minolta 100mm macro with Kenko 2x teleconverter



Flash can also be used with teleconverters. TTL-metering will take care of flash exposure. Just remember to check flash to subject distance. With a teleconverter attached, you loose 1 or 2 stops of light. You may have to get closer to your subject to make sure enough light will reach the subject. You can easily check this by referring to your flash guide number or flash-to-subject distance which is shown on flash LCD panel with most models at most f-stops. Lets say you are using a 200mm f-2.8 lens with a 2X teleconverter. The combination results in a 400mm f-5.6 lens. The procedure for determining flash-to-subject distance is the same as if you were using a 400mm f-5.6 lens. Focus on your subject and check the focusing distance mark on your lens. Check to see the f-stop you want to use covers this distance. It is shown on your flash LCD panel.
By the way, some manufacturers have two versions of their 2X teleconverters: 4 element and 7 element. 4 element types cost less than 7 element models, but 7 element teleconverters produce much better results. If you can, purchase the 7 element version.

 

Recommended Equipment Kenko Teleplus PRO 300 AF 1.4x Teleconverter & Kenko Teleplus PRO 300 AF 2x Teleconverter   1.4X:  KENKO Teleplus Pro 300 converters are made with high quality multicoated optical glass supplied by Hoya corporation, the worlds largest manufacturer of optical glass. This glass will match the optical quality of the prime lens (even at the edges, unlike many teleconverters on the market today). The optical design of the elements and light path is wide enough not to cause any vigenetting. They are designed specifically to be use with telephoto lenses of 100mm or above, and work best with telephoto lenses of 200mm to 500mm. The PRO 300's can be used with telephoto zoom lenses as well as prime lenses, but, due to their design, Kenko does not recommend them for lenses that have a zoom range that starts under 50 mm. Kenko PRO 300 converters are intended to be used with expensive telephoto lenses and larger camera bodies. They have all metal lens mounts in both front and rear, as well as a metal core, to support today's heavy professional camera bodies. 2X: KENKO Teleplus Pro 300 converters are made with high quality multicoated optical glass supplied by Hoya corporation, the worlds largest manufacturer of optical glass. This glass will match the optical quality of the prime lens (even at the edges, unlike many teleconverters on the market today). The optical design of the elements and light path is wide enough not to cause any vigenetting. They are designed specifically to be use with telephoto lenses of 100mm or above, and work best with telephoto lenses of 200mm to 500mm. The PRO 300's can be used with telephoto zoom lenses as well as prime lenses, but, due to their design, Kenko does not recommend them for lenses that have a zoom range that starts under 50 mm. Kenko PRO 300 converters are intended to be used with expensive telephoto lenses and larger camera bodies. They have all metal lens mounts in both front and rear, as well as a metal core, to support today's heavy professional camera bodies.