Using Stacked TC's on a 60D

Started May 26, 2011 | Discussions thread
Doug J
Veteran MemberPosts: 7,820
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Re: Why taped?
In reply to Birdman50, May 29, 2011

Birdman50 wrote:

biochemiker wrote:

I've tried the taping thing before but that only helps with phase detect AF. Live View AF doesn't care if the TCs are there or not and will AF at f/8 or f/11.

They're both taped in case I need one only for my 400 mm. f/5.6L. I just taped both for convenience. Yes, in LV, taping will not matter, but I don't use LV all the time.

I think this math is a bit off... The focal length is 800mm at f/11 with two 1.4x TCs.

How did you get the 800mm FL? 400X1.4X1.4= 784mm. Is there a new way of computing this that I should know about?

A very minor point relative to 1.4 x 1.4 versus 2.0 and least significant digit rounding. The difference is a factor of 0.04, or 16mm at 800mm; irrelevant in actual shooting.

I typically use the multiples as you do (1.4 x 1.4, 1.4 x 2.0) and don't worry about stating a few mm difference.

Cheers,
Doug
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