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agiaccio · Apr 6, 2005, 1:57 PM

I'm looking at purchasing a good-quality telephoto lens for using outdoors and indoors (well-lit church) on my new Canon 20D. I've narrowed my choices down to the following two Canon lenses:

Canon EF 70-200mm F4.0L USM
Canon EF 70-200mm F2.8L USM

I would like to use the Canon Extender EF 1.4x II on my new telephoto lens but the documentation says that the "effective aperture will be reduced by one f-stop" when using this extender.

What will be the effect on the F4.0L lens? Will it still be useable indoors? Would I require "lots" of light? How big of a difference would it be between these two lenses? My budget is just right for the F4.0L lens but unfortunately the F2.8L lens would cost an additional $650 Cdn.

PeterP · Apr 6, 2005, 2:14 PM

:-)

The F2.8 lens with a 1.4TC becomes a F4.0 lens.

The F4.0 lens with a 1.4 TC becomes a F5.6 lens.

The 1.4 TC will work with both lenses. Each stop difference cuts the transmitted light in half. You rarely shoot with the lens wide open if you want any depth of field so you will most probably be shooting closed down a stop or two. I'd suggest a good flash would be needed, or a tripod and short time exposures for indoor shots.

Peter.

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Apr 6, 2005, 1:57 PM	#1
agiaccio Senior Member Join Date: Jun 2002 Posts: 274	I'm looking at purchasing a good-quality telephoto lens for using outdoors and indoors (well-lit church) on my new Canon 20D. I've narrowed my choices down to the following two Canon lenses: Canon EF 70-200mm F4.0L USM Canon EF 70-200mm F2.8L USM I would like to use the Canon Extender EF 1.4x II on my new telephoto lens but the documentation says that the "effective aperture will be reduced by one f-stop" when using this extender. What will be the effect on the F4.0L lens? Will it still be useable indoors? Would I require "lots" of light? How big of a difference would it be between these two lenses? My budget is just right for the F4.0L lens but unfortunately the F2.8L lens would cost an additional $650 Cdn.

Apr 6, 2005, 2:14 PM	#2
PeterP Senior Member Join Date: Jul 2003 Posts: 3,397	:-) The F2.8 lens with a 1.4TC becomes a F4.0 lens. The F4.0 lens with a 1.4 TC becomes a F5.6 lens. The 1.4 TC will work with both lenses. Each stop difference cuts the transmitted light in half. You rarely shoot with the lens wide open if you want any depth of field so you will most probably be shooting closed down a stop or two. I'd suggest a good flash would be needed, or a tripod and short time exposures for indoor shots. Peter.