 BetterPhoto Member |
2 x Converters I have a Nikon F50 camera 35-70 lens 70-210 and a 170-500mm lens for scenery, wildlife, concerts, etc. Can you let me know? thanks, Gord>>>>>>
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Jon Close |
A Teleconverter will decrease the effective maximum aperture of the lens you use with it. A 1.4x TC decreases the aperture by 1 stop (f/5.6 becomes f/8) and a 2x TC decreases by 2 stops (f/5.6 becomes f/11). Most autofocus SLR's will lose autofocus ability if the effective aperture is smaller than f/5.6. This loss of light also darkens the image in the viewfinder somewhat, which may hamper manual focusing in low light. Because of this, teleconverters are most effective when used with "fast" lenses (maximum apertures of f/1.0 to f/2.8). I'm assuming your lenses have maximum apertures of f/3.5-5.6 (f/5-6.3 for the 170-500 zoom). You can use a 2x TC with your lenses, but you will have to use manual focus.
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John A. Lind |
Gord, A TC is always a compromise. Along with what Jon mentions, many TC's are not the best optically (especially the "generic" inexpensive ones). You will lose resolution and contrast with them. The lesser ones will also introduce aberrations, including chromatic. This is separation of colors or "fringing" at the boundary of two different colored objects in the image. How much compromise there is will depend on the TC design. The best ones have 5 to 7 multi-coated elements, are "matched" for use with specific lenses, and are somewhat expensive. Having had a generic (non-OEM), inexpensive, uncoated, 2 element 2X TC, I will attest to their general lack of optical quality. It was quite noticeable in the images made using it. Most problematic with image quality is combining a TC with a zoom lens, unless the TC is specifically designed for use with that particular zoom. In general, better results are had in using a TC with a prime lens, not a zoom. Your results may vary with combinations of specific lenses with specific TC's. Two years ago I would have steered people away from using a TC. I now have, and occasionally use, a 2X TC for my SLR system. It was made by the OEM, was specifically designed to match several of the faster OEM prime telephotos it is used with, and has 7 elements of multi-coated ED glass. Although very expensive for a TC, it was still considerably less expensive than buying 400mm and 600mm prime telephotos that would be used very occasionally. Even at over five times the cost of the generic TC I no longer use, its performance is much, much, much better. Research the TC's available for your camera system and the lenses you have very carefully before buying one. If you suffer sticker shock looking at the best available, remind yourself of the cost for a lens in that focal length. -- John
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