Would an extender w/ my 70-200 2.8 IS mean I can get rid of my 100-400mm?

Curious...I've never used an extender before and been reading up on them here. I see alot of people using 70-200mm F4 IS in conjunction with an extender for extra reach (instead of purchasing a 100-400). Compared with the F4 version I know the 100-400 is better because you lose 2 extra stops on the 70-200 with the extender right?

But what about the 2.8 I wonder... Would that mean that you actually end up with about the same F-stop as the dust pump after adding an extender to it?

Yeah but your image quality is gonna take a big hit, especially with a 2x. Contrast and bokeh are the first things to go when attaching an extender, AF speed and accuracy suffers, and resolving power goes to all hell - all of which are gonna make your images softer too. 1.4x extenders are OK - I dunno how they work on a 70-200 2.8, but my big beef with them is that they tend to make bokeh really ugly.

perryge wrote in post #7504552
Yeah but your image quality is gonna take a big hit, especially with a 2x. Contrast and bokeh are the first things to go when attaching an extender, AF speed and accuracy suffers, and resolving power goes to all hell - all of which are gonna make your images softer too. 1.4x extenders are OK - I dunno how they work on a 70-200 2.8, but my big beef with them is that they tend to make bokeh really ugly.

Thanks for that...I was wondering if I could sell my 100-400 to get me an unexpected new lens on my wish list. I started getting excited and now you've rained all over my parade....

Rhilton4u wrote in post #7504572
Thanks for that...I was wondering if I could sell my 100-400 to get me an unexpected new lens on my wish list. I started getting excited and now you've rained all over my parade....

You could sell it and buy a Sigma 120-300 f2.8 with a 1.4 tc, you then get 168-420mm at f4. mmmm

As stated, i dont think an extender could ever replace a real lens, unfortunately.

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You'd be missing a lot of range compared to the 100-400 as well.

perryge wrote in post #7504552
Yeah but your image quality is gonna take a big hit, especially with a 2x. Contrast and bokeh are the first things to go when attaching an extender, AF speed and accuracy suffers, and resolving power goes to all hell - all of which are gonna make your images softer too. 1.4x extenders are OK - I dunno how they work on a 70-200 2.8, but my big beef with them is that they tend to make bokeh really ugly.

Interestingly, with extenders barrel distortion causes the center portion of the image to be slightly enlarged - making it appear to resolve more detail.

The 2x converter reputedly degrades the image more than the 1.4x converter - I've only used 1.4x. I've used it with the 70-200 F4 & F2.8 IS and the 300 F4 IS. It worked really well with all these lenses especially when stopped down a little from wide open (e.g. with 300F4, add converter max aperture is f5.6, at f6.3 was really good).