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DPChallenge Forums >> Hardware and Software >> Help with tele-converters
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AuthorThread
 12/26/2005 11:55:34 AM · #1
I need some help deciding. I am wanting to extend the range of my 75-300 IS USM Canon f4-5.6 on a Canon 20D.

I want this for strictly outdoor photography, well lit scenarios. Does anyone have any recomendations and experience with 1.4 or 2.0 converters?

Thanks,
 12/26/2005 12:09:04 PM · #2
You can't use a teleconverter on that lens.

A 2.0 TC will 'csot' you 2 stops of light - to the 5.6 becomes f11 - and your camera will not autofocus if the max fstop is more than 5.6. It might work if you use a non-canon converter, but don't expect great results.

a 1.4x will cost you 1 stop of light, still pushing you over the 5.6 limit.

To use these you need an F4 or F2.8 lens.
Click the pic and read it -

12/26/2005 12:19:58 PM · #3
With that lens you can't use the Canon teleconverters as they are designed for the L series lenses, mostly primes.

Third party teleconverters are available and from what I've read (I don't use any) the 1.4 performs much better than the 2.0.
 12/26/2005 12:24:13 PM · #4
I recently got a tamron 70-210 2.8 and borrowed 2 tamron converters and tried some test shots. I see vey little image quality reduction. Some sure, but not sure that it would even be noticeable in an 8x10 print. Might depend on the subject as much as anything.
the 210 alone
with the 1.4
with the 2.0
with both - 940mm effective focal length



Message edited by author 2005-12-26 12:24:55.
 12/26/2005 01:18:26 PM · #5
Thanks that helps a lot. Not much perceptible loss of quality on the shots.
 12/26/2005 01:30:45 PM · #6
I have used a 1.4 teleconverter on a 6.3 lens before. It works in good light. The autofocus can start hunting in low light but you can still use it and switch to manual focus. This is the lens:

Tamron 200-500
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