Can anyone explain this ?

magpieant

magpieant

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Righty - I'm confused (for the good, but still confused).

I used to use Nikon. With that setup, I had a 2x TC - a Kenko one. The TC used to take the equivalent of 2 stops.

I now use canon. I currently have a 70-200 2.8 attached. i have also just purchased a x2 TC. I thought that it would take up 2 stops - meaning the minimum aperture would be 5.6. However, it's still letting me use 2.8.

How can this be ?

Or is it quite simply a case of it will still let me use f/2.8 - but with 2 stops slower on the shutter speed ?

Not sure if I have just answered my own question!

Help!

Anth
 
Yes you have, it's saying 2.8 but if you compare the exposures with and without the converter you'll find a difference, it may not actually be 2 stops, they vary a bit. Wayne
 
F/5.6 is the effective aperture in total, not actual aperture of the lens.
 
Cheers folkies.

Started typing the question and then realised I was answering it myself!!!!

Sometimes we all seek confirmation in life - and I know I can always rely on you lot!

Anth
 
Not sure about this :thinking:

If you fit a 2x extender to your 70-200mm f/2.8 lens, it becomes a 140-400mm f/5.6. Not just 'effectively' but that is its actual new spec. But the camera only knows what it is being told by the extender - what model is it?

When I fit an extender (Kenko Pro) to my Canon 40D, the f/number readout changes accordingly, as it should.
 
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