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  1. #1
    Join Date
    Feb 2006
    Location
    Des Plaines, IL
    Posts
    9,554

    Question Tele-converters? Safe to use ... or what?

    A lot of new photographers ask about the bane of lensmen … ye old tele-converter (or T/C).

    Yeah, those little 1.4x, 1.7x, 2x or 3x fittings you sandwich between you camera body and the lens you use, supposedly providing you will instant longer lens.

    My advice:

    Do NOT be so quick to buy into that idea. While these cheap additions may seem attractive to the photographer on a budget, the image quality goes to heck, real quick, turning your beautiful 70-200mm f/2.8 zoom shot … into a longer, darker, un-sharp image producer.

    Always consider buying a better lens, first, unless there just is no way you can pop for it.

    The fact is, placing a tele-converter on a 200-500mm f/5-6.3 lens takes away the lens’ infinity focus. Yeah, no kidding. What that means is if you are shooting anything beyond 27 feet from the end of your lens … it is out of focus (OOF). The actual lens focusing mechanism cannot compensate for the additional gap you have just inserted by adding the tele-converter into the mix. So, while you may want to get that bird sitting way up in yonder tree (one hundred yards away) … with your newly created home-made 400-1000mm f/11-13 monster … it will never look sharp. So what's the point? "Yeah, I got the shot!" I don't think you are going to be all that impressed by the result. I know I certainly wasn't, when I did it.

    So, be aware that infinity focus, on many lenses will become unusable, once you add this device to your lens.

    Using the TAMRON SP AF 70-200mm f/2.8 Di LD MACRO, here are a series of shots taken at 10-feet ... @ 200mm (no T/C); 280mm (1.4x T/C); & 400mm (2x T/C). I had to manually monkey around for the flash to have enough pop to maintain the base f/8 aperture (TTL really gets confused when using a T/C, also, so the “pop-up” flash is effectively useless, even if you try to jack up the flash exposure setting. )

    NO T/C
    Name:  70-200-no-tc.jpg
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Size:  317.8 KB

    1.4x T/C
    Name:  70-200-14x-tc.jpg
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Size:  327.1 KB

    2x T/C
    Name:  70-200-2x-tc.jpg
Views: 120
Size:  236.0 KB

    You need to bear in mind that stopped down to f/8 or tighter, these all are going to look acceptable ... if you try to go with a wider aperture ... then the images degrade (see below):

    2x T/C wide-open aperture
    Name:  70-200-2x-tc-wide-open.jpg
Views: 116
Size:  201.8 KB

    So, use them as you like, but be prepared for the drawbacks. There are a few.
    Last edited by DonSchap; 11-09-2008 at 09:10 PM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

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