Do Extenders work well?

[debiharry]

Hi, I have a canon 10D and I wanted to use an extender 1.4X with my Canon 70-200mm 4.0 L USM lens. I wanted to know if an extender would cause excessive camera shake as I prefer to hand hold for most of my shots. Has anyone used this combination with success? Thanks for any help.

[Michael Fanelli]

Hi, I have a canon 10D and I wanted to use an extender 1.4X with my Canon 70-200mm 4.0 L USM lens. I wanted to know if an extender would cause excessive camera shake as I prefer to hand hold for most of my shots. Has anyone used this combination with success? Thanks for any help.

The extender has glass in it and really does change the focal length (unlike the "equivalence" 1.6X of the sensor). Unless you are shooting at high shutter speeds, you will need a tripod. Use the 1/FL rule as a guideline.

[paulnj]

as to success.. a person on a birding group I belong to uses the 20D/70-200f4/canon 1.4 extender with great success handheld.

To add to Mr Fanelli's post....

I find that the 1/ focal length rules needs a bit of adjusting with digital compared to film. The focal length would be 280mm on film with that setup, but with the smaller sensor the image from that setup would have the PERSPECTIVE of roughly 450mm on a 10D . The 420mm is the number I would use as my focal length.

[another view]

Paul, how did you get 420mm?

200mm x 1.6 (digital crop factor) = 320mm.

320mm x 1.4 (TC) = 448mm.

I guess it really doesn't matter - especially in this case, 420 and 448 are close enough here - but I'm curious.

[another view]

You can lose some sharpness with an extender and a zoom. You probably will but how much depends on if it's kind of a "matched set" where a specific TC (tele converter) is recommended with a specific lens. Nikon has something like that, and Canon probably does too. In this case, you shouldn't see much of an effect - but in general zooms & TC's don't play well together.

You'll also gain 1.4X the focal length meaning you'll need a higher shutter speed for handholding. And you'll also lose one stop because of the TC (2X TC's = 2 stops, BTW).

Because of this, you may end up using higher ISO's than you're used to. For example, your minimum aperture is now f5.6 with the TC, and your effective focal length (counting the 1.6 digital crop factor and 1.4X TC) is about 450mm. Starting at 1/500 sec for a shutter speed would be a good idea, faster if possible. You may be able to hand hold slower than that but it will take some practice. Also note that f5.6 is typically the minimum aperture that's useable with autofocus. You might see your AF work slower and/or not as accurately in some conditions.

Now think about the Sunny 16 rule. If you're not familiar with this, it basically means that your exposure is the reciprocal of the ISO speed at f16 on a sunny day. ISO100 = 1/125 at f16, etc. Cloudy days will need one to three or more stops extra exposure.

OK - where am I going with all this? On a bright sunny day, that translates to 1/500 (which we need, right?) at f8. The widest aperture you now have is f5.6. So any lower light (more than a stop), or even a light cloud cover and you'll start bumping your ISO up to 200, 400 and up from there. I'm not saying this won't work, but it's something to be aware of.

[paulnj]

Paul, how did you get 420mm?

200mm x 1.6 (digital crop factor) = 320mm.

320mm x 1.4 (TC) = 448mm.

I guess it really doesn't matter - especially in this case, 420 and 448 are close enough here - but I'm curious.

I guess now isn't a good trime to tell you I tutored math in high school huh ;) I actually was thinking the right number but my finger typed otherwise .. and I am sticking to that story

[another view]

.. and I am sticking to that story

So - the "new" math, eh?

I typed my long reply first, then saw yours and then typed that reply about how you got 420. But it shows up that I posted it two minutes before the first one. Can you explain that one? I can't!