# Advice on a teleconverter



## TexasAggie07 (Jun 30, 2011)

Howdy guys, 

I have a Cannon 60D and a Cannon EF 70-300mm 1:4-5.6 IS USM lense and I was wanting to get a teleconverter for it. I would much rather buy a longer lens but that is not in the cards atm. I was wondering if anyone knew if the Cannon teleconverters either 1.4 or 2x would work on my camera lens, it is not listed in the compatability chart. I am wondering 1) will it even hook up to that lens and 2) will any of the autofocus features work with it?

Thanks for the help guys!

Brian

Oh and also on a side note there are alot of lenses for cheap from Bower that are like 1300mm or something crazy like that for under 300 bucks are these worth buying to play with or are they expensive paper weights. I have no ambition to go pro with this just a very addicting hobby!


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## joealcantar (Jun 30, 2011)

From what I remember 5.6 is the key # as once most cameras go beyond this you lose the autofocus funtion on most of them.  So with the lens you have and it being 4.0-5.6 I would choose the 1.4 if it converts to 5.6 on the lower end of the lens scale , but once you zoom out to 300mm you will go beyond that and lose the auto focusing. 
Here is an article with some good info and mentions your camera: 
Teleconverters and autofocus: What every wildlife photographer should know | Improve Photography
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Shoot well, Joe


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## TexasAggie07 (Jun 30, 2011)

Thanks! That was a very informative read!


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## Big Mike (Jun 30, 2011)

That's right.

Most cameras need F5.6 or larger, in order to get enough light for the AF system to work properly.  Teleconverters 'eat' some light.  I think it's about 1 to 1.5 stops for a 1.4X and about two stops for a 2.0X.  So if you put a teleconverter behind a 'slow' lens like that, your camera won't be getting enough light for the AF and it may not work.  

Actually, Canon has a short list of lenses that are 'compatible' with their teleconverters...and they are F2.8 primes or zoom...maybe an F4 but I'm not sure.  I'm not sure if you could use a Canon TC with that lens or not.  You could certainly use an off-brand TC, but the same AF issues exist.  I have a Tamron 2X TC that I occasionally use with a 70-300mm lens....and yes, AF usually doesn't work.  Not to mention that the image quality is hit or miss as to whether it's going to be better than just shooting at 300mm and cropping the image later.  
And that may be a decent option for you.  The 60D has 18 megapixels, which should be plenty of room for cropping, provided that you maximize the sharpness of the photo (fast shutter speed, tripod etc.)  


> Oh and also on a side note there are alot of lenses for cheap from Bower that are like 1300mm or something crazy like that for under 300 bucks are these worth buying to play with or are they expensive paper weights. I have no ambition to go pro with this just a very addicting hobby!


There are a few reviews of lenses like that, maybe even a thread or two on this forum (a few years ago).  I think that the general consensus is that they might be fun to play with, but the image quality is so far below what you would want...that the images are all but unusable.  Also consider how hard they would be to shoot with.  I think the typical scenario is a 500mm or 800mm lens with a fixed aperture of F8.  Then then include a 2X TC, giving you 1000mm or 1600mm and an aperture of F16.  
Now, if you know anything about exposure...in anything but really bright sunlight, F16 is going to require a rather slow shutter speed.  And because of the huge focal length, you would need a really fast shutter speed to get a shot without blur from camera shake.  Even with the rig on a good tripod, something that long is going to move a little and give you blur at that focal length.


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