Canon EF 70-200 f/2.8L and the IS version

[Jeff Canes]

The aperture shouldn't change. a 2.8 will stay a 2.8, an F4 will remain an F4..... If I'm wrong, please correct me.

Aperture does not change physical size, but it size denotation and effect does. WHAT! There is this math formula that I never learned and do not planed to that determines the aperture size. By adding an extender you change variables and the out come of the formula

with the 2x on the 70-200 it goes up F64

 

[DonSchap]

You might say the Teleconverter reduces the amount of light that gets to camera's sensor by 1-full f/stop. That means... if your aperture is set to 2.8 (indicated) and you have the EF 1.4x attached... the actual light to the sensor is at f/4 levels.

I have found that the Canon EOS 20D does have the intelligence to know when one of the higher end T/Cs (Canon's EF 1.4x or EF 2x... or TAmROn's SP1.4x or SP2x) have been added on the the camera... it does indicate no less than f/4. In other words... it cannot indicate the lens' f/2.8 maximum aperture, the EOS 20D now knows it is not possible.

With other teleconverters (the cheap, low-end ones), only the actual camera's light metering will indicate this change (as the T/Cs do not offer this intelligence). The f/stop indicator will play stupid and still read f/2.8 when it really is not, so you have to trust the camera's actual metering for proper exposure... and realize your depth of field (DOH) has changed accordingly. You are not going to see f/2.8 bokeh.

If you use an EF 2x teleconverter, you will lose 2-full f/stops of light through it. Taking the f/2.8 to f/5.6 response.

That's what happens, folks. Put one on... and see for yourself!

BTW... if you can, use high-end T/Cs. Especially with the good glass. You may think your lens is fast... but with a crappy t/c on it... it's probably just half-fast.

 

[HoboSyke]

Thanks for all the replys and good comments guys!

 

[thebeginning]

the IS is great. I'm quite glad i got the IS version...at first i was worried it would be soft, but it's sharp (very sharp from 70mm-175, sharp at 200mm...i only measure by wide open as that's mostly what i shoot...at 3.5-f4 it's tack sharp at all focal lengths). I also realized that comparing 200mm (usually the softest part of a zoom) wide open to the 85mm 1.8 stopped down to f4 wasn't a fair comparison . once you see that you can get 200mm shots at 1/30, you'll be very glad you bought the IS. if you use a tripod most of the time and shoot outdoors alot, it's not as big of a deal. if I knew I'd never do anything lowlight handheld, i might have got the non IS as it's lighter and cheaper. but i do shoot alot of lowlight and almost all handheld, so that made my decision for me.