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 Post subject: Canon extenders
PostPosted: Mon Apr 25, 2011 10:14 am 
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Location: Chennai
Hi All

I am planning to upgrade to 7d from 50d. Now i wanted also to buy extenders for my current 70-200 2.8 L lens. I find two extenders in canon range and they are 2X II and 1.4X II . Which one do you recommend to me?

I also heard that we have to compromise on aperture as my F2.8 will no longer be 2.8 and i can start only from 5.6 or so? Why is that we need to compromise on aperture?

Please shed some light to me so that i can get one when i get my hands on 7d .

Thanks a lot.

Cheers
Mano

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Canon EOS 5D mk III|Canon EOS 7D | 70-200 F2.8 L IS II USM | 400 F5.6 L USM


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 Post subject:
PostPosted: Mon Apr 25, 2011 10:36 am 
A 1.4x teleconverter will give you a 100-300mm f4

A 2x teleconverter will give a 140-400 f5.6

EDIT: Removed this section as Bob explained it better below!

The image quality declines as the extender get larger, ie the 2x gives worse quality than the 1.4x

What Id recommend depends on what you're doing really, ie how much extra length you need. If you only need up to 300, buy a 1.4, rather than using the 2x but zoomed only half way. If you need 400mm, buy the 2x


Last edited by jeremy1302 on Mon Apr 25, 2011 10:38 am, edited 1 time in total.

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 Post subject:
PostPosted: Mon Apr 25, 2011 10:37 am 
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Hi Mano and Jeremy,

If you remember that f-number is just the focal length of the lens divided by its aperture then you'll see why using a 2x extender, which doubles the focal length, also doubles the smallest f-number your lens can achieve.

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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 Post subject:
PostPosted: Mon Apr 25, 2011 10:57 am 
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i'm gonna give it a shot at explaining the aperture...

we will be thinking this on a fixed aperture (say f2.8 )

you see the diameter of the 'hole' in your lens stays fixed and is not changed by the fact that you insert extenders between the lens and the camera. you move the hole thing. but the focal length of the lens depends on the distance to the sensor, and thus it is increasing.
if you use 2x extender, means that you doubled the focal length. now if the diameter of the pupil stays still you get something like this:

d=f/2.8

and if you double the f (focal length) to have d (diameter) constant you also need to double the 2.8 number (making it into a 5.6) so the equation stays valid.. ;)

hope you understand

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PostPosted: Mon Apr 25, 2011 12:36 pm 
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Thanks Jeremy , Bob and bakica

My intention is to shoot birds and what i realised(last time when i shoot them) my current lens 70-200 is not sufficient as i couldnt reach them enough close. So thought of buying extenders , so here is what i thought to get opinion from you guyz whether to go for 1.4x or 2x. I believe , the reason why i wanted to go for 2x is , after i buy 1.4x , what if i still couldnt get them :( .. so thinking of going for 2x . I cant invest my money now on another lens which is 300mm or 400mm and definitely i cannot shoot without IS with such focal length , so with IS i am sure i am close to another bomb which will blow me off completely.. Instead of buying one more expensive lens , just thinking to stick to one of these extenders and get satisfied.

Any suggestions on this?

Regds
Mano

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Canon EOS 5D mk III|Canon EOS 7D | 70-200 F2.8 L IS II USM | 400 F5.6 L USM


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 Post subject:
PostPosted: Mon Apr 25, 2011 12:47 pm 
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.
As the question is now Canon specific I'll move the thread.

Bob.

_________________
Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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 Post subject:
PostPosted: Mon Apr 25, 2011 12:56 pm 
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Thanks Bob :)

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 Post subject:
PostPosted: Wed Apr 27, 2011 6:12 am 
Hello Mano,

I have the Canon 70-200mm f/2.8 L and the Canon 400mm f/5.6 L. I also have the Canon 1.4x II extender, and was able to borrow a Canon 2x II extender from a friend for a couple days about a week ago. So naturally I decided to test these two lens with different combination of the extenders to see how they preformed. I have been planing to write up a review with my findings, but I'm a college student so I have been very busy.

Seeing how you need help decided what to do I figured I can show you some of the results from the test. Now keep in mind that I don't test lens all the time and this was my first time doing something like this. But I did do the test multiple times to ensure that I got a good sample.

Here is the uncropped comparison of the different focal lengths all with the 70-200 f/2.8 non IS. 200, 280(1.4x), 400(2x)

Image

Now here are the 100% crops all of which were stopped down 1 stop from wide open.

Image

Now at 400 the image quality is fair, some samples at 400 were slightly better, while some were slightly worse. I did let the camera use auto focus. But in general the results show a loss of image quality and that is to be expected.

With that said I did go out and take field shots and here is a comparison between the 70-200 with 2x extender and my 400, both taken at f/8

Image

Now in the field I find it hard to see a huge difference between the two.

The person that I borrowed the 2x extender from uses it on her 70-200 f/2.8 II, the same lens you got and she seems to be happy with it. Any time we go take pictures she puts it on and takes nice pictures. So hope this helps, I'll try and check back to answer any questions you might have.

-Cord


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 Post subject:
PostPosted: Wed Apr 27, 2011 6:21 am 
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Hi Cord

Excellent ! Thanks a lot for taking time and providing me with some results. That was fantastic honestly.. Now you erased my confusion and yes i am going for 2x , anyhow for the time being i am in no position to buy one more L lens and pretty happy with the one i am having currently and i'll use this extender only on this lens for the time being , having said that , i am going to own this extender for sure.....

Once again thanks a ton for your review and that too with clear pictures.

Regds
Mano

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Canon EOS 5D mk III|Canon EOS 7D | 70-200 F2.8 L IS II USM | 400 F5.6 L USM


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 Post subject:
PostPosted: Wed Apr 27, 2011 6:24 am 
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Joined: Thu May 29, 2008 3:02 am
Posts: 444
Location: Chennai
Cord

BTW , i wanted to ask you on this question. In one of the photos you mentioned that 70-200 F2.8 2x(photo of tortoise) but i heard that the f stop will no longer be 2.8 and will be 5.6 once we start using with extenders? How come you shoot that with 2.8 still? or am i totally wrong?

Regds
Mano

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Canon EOS 5D mk III|Canon EOS 7D | 70-200 F2.8 L IS II USM | 400 F5.6 L USM


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 Post subject:
PostPosted: Wed Apr 27, 2011 3:46 pm 
Yes your right that I just meant that it was the Canon (70-200 f/2.8 lens) with 2x extender. So with the 2x extender the lens becomes a 140-400 f/5.6, sorry for the confusion there. I think you will enjoy the 2x extender and it sure does beat spending a ton a extra money.


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