Canon Extender

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    I have a 70-200mm 2.8 and I’m lacking a little range for some wildlife photographs. I’m thinking about getting a

    Canon Extender EF 1.4x II
    Canon Extender EF 2x II

    but I’ve heard that you loose some picture quality…but how much is “some”? Does anyone have an extender and can comment on the photodegradation.


    You lose both f-stops and quality.

    The f-stops is simple. A 2x adds 2 stops and a 1.4 adds 1 stop (rounded). This is due to the fact that you are changing the focal length while keeping the lense diameter the same. F-stop is Focal length/diameter. So if you have a F/2 lense it is now a f/2.8 with a 1.4x and a f/4 with a 2x.

    Here is the modern f-stops:
    f/0.7, f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64, f/90, f/128

    So if you have a zoom which is f/5.6 on the long end (common on the bundle lenses) it would be a f/11 with the 2x at the long end!

    As far as quality, you add glass surfaces so it will hurt some. A 200mm lens usually will outperform a 100mm with a 2x.

    Any way I have used a 2x with my Pentax and Zenit cameras and I am happy with it. I actually have used a 3x with a 300mm prime before too and was happy with the results.


    Tamron AF 28-75mm f2.8 becomes:
    39 – 105 f/4 with a 1.4x
    56 – 150 f/5.6 with a 2x

    Canon EF 50mm f/1.4
    70mm f/2 with a 1.4 x
    100 f/2.8 with a 2x

    Canon EF 70-200mm f/2.8L
    98 – 280 f/4 with 1.4x
    140 – 400 f/5.6 with 2x

    You have reasonably fast lenses so the converters wont hurt too much.


    I was looking to use it with my 70-200, just so I could have a little reach. I think I’m gonna buy the 2x and if I don’t like it, I’ll just sell it on e-bay.



    Hey Slowpoke, is your 70-200mm a constant aperture? IE f/2.8 at all ranges? I am not too familar with the Canon offerings.

    Does the Canon 2x have a mcro mode? My Vivitar 2x for the K-mount does and I have gotten very good results with it. I used it with a Sigma zoom for my light bukb macros in the contest a couple of weeks back.


    It is generally believed that a 1.4x teleconverter doesn’t degrade the picture much at all. However, a 2x does. Since I’m using Nikon I went for the 1.7x for my 70-200, but I’m not sure if Canon has any 1.4x teleconverters available.


    I have the 1.4x Canon Extender. I typically connect it to my f4 70-200mm (Slowpoke’s lens’ baby brother). I’m completely happy with it, but I haven’t done any sort of controlled resolution/color tests.

    I shied away from the 2x since I’d heard about image degradation with that one.

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