 BetterPhoto Member |
The Ins and Outs of Tele-Converters I own a Minolta 404si SLR camera and have just purchased an AF 75-300 lens. I would love to have a 100-400 but these are very expensive. What are telephoto converters and how good are they? I mainly want to be able to zoom right in on sporting games. I have very limited knowledge regarding lenses and would love and appreciate any advice I can get!
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
Tele-converters double the focal length by acting like a magnifying glass between the lens and your camera body. And essentially that's what they do: They magnify the central part of the image. So the up side is it's a cheaper way to get a longer focal length, but the down side is that the usable maximum f/stop is reduced depending on how much the converter increases the focal length. And depending on the quality of the converter, you do get a decrease in contrast, and sharpness. How noticeable depends on the converter and the lens you're starting with. Your lens is probably a f/5.6, so if you were to add a 2x converter, the image you'd get would be like you were using a 150-600 zoom lens. But your biggest effective f/stop would be f/11. And you'd also have a darker view finder, so you wouldn't be able to shoot at night with that. And image quality may suffer with a 75-300 connected with a converter - well, at least a 2x. The higher the conversion, the greater the contrast and sharpness suffers. You also wouldn't be able to use autofocus, if you do use it. I don't know if anybody has a converter to fit that lens. Some manufacturers, their converters only fit some of their lenses. But there are also 1.5 converters, or close to it, like 1.4. With that, you don't get the magnification of a 2x, but you don't get the loss of 2 f/stops. You only lose 1, so the effective aperture would be f/8.
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Michael McCullough |
Kiron has made some very good teleconverters in the past you might pick one up in the used market, look for 7 element 2x or 5 element 1.5!!!!
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Peter K. Burian |
The Tamron and Sigma teleconverters fit many (but not all) zoom lenses. The only way to be absolutely sure is to ask a dealer or to take your lens to a dealer and try it yourself - if they have a suitable converter in stock. Peter Burian
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