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Posts: 1
Registered: ‎12-09-2020

lense extender for a Canon Rebel 3ti - 55-250 mm lense?

I have the above camera and lense.  I was wondering if I can use a 1.4 or 2.0x lense extender, instead of buying a telephoto lense, say 100-400mm.  What will happen to autofocus and quality of pictures? 

VIP
Posts: 11,804
Registered: ‎08-13-2015

Re: lense extender for a Canon Rebel 3ti - 55-250 mm lense?

You will lose the ability to autofocus.  Extenders are made for lenses with a maximum aperture of f/4, or faster.  Advanced bodies can work with f/5.6 lenses, but not an entry level Rebel.

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"Doctor told me to get out and walk, so I bought a Canon."
Esteemed Contributor
Posts: 4,811
Registered: ‎02-17-2016

Re: lense extender for a Canon Rebel 3ti - 55-250 mm lense?

The Rebel will focus at f/5.6 at the center point, according to the specs.

 

All the points on my T6S are f5.6:

"All AF points are cross-type at f/5.6"

VIP
Posts: 11,804
Registered: ‎08-13-2015

Re: lense extender for a Canon Rebel 3ti - 55-250 mm lense?


@kvbarkley wrote:

The Rebel will focus at f/5.6 at the center point, according to the specs.

 

All the points on my T6S are f5.6:

"All AF points are cross-type at f/5.6"


Not with an extender.....

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"Doctor told me to get out and walk, so I bought a Canon."
Respected Contributor
Posts: 1,458
Registered: ‎01-25-2018

Re: lense extender for a Canon Rebel 3ti - 55-250 mm lense?

[ Edited ]

Canon doesn't support a lens extender for this lens model so if one is available it would have to come from a third party.  Because even a 1.4X would put your lens at F8 once you are barely past the widest angle, your 3ti won't autofocus with an extender.

 

Even the best quality primes suffer a loss of sharpness and quality with a 1.4X but because they are so sharp to start the dropoff is somewhat acceptable.  I have used a 1.4X with my EF 300 and 400 f2.8 lens at times but even with those there is noticeable degradation.

 

Depending upon what you are shooting, the combination of any slow lens and the further loss in stop(s) due to converters may put you into a light challenged situation at times when you need a lot of shutter speed to freeze subject motion.   There are occasions where I go with the shorter focal length of my EF 400 f2.8 and use tighter cropping rather than give up the two stops of light from using my EF 800 f5.6.

 

An often overlooked Canon prime that has a nice price to performance ratio is the EF 400 f5.6.  It is very manageable for a 400mm, provides nice sharp high contrast photos, and has very fast focus acquisition.  I bought one with my first Canon 1 series digital back in 2005 and I have kept it because it is a nice performer and more comfortable for taking on hikes compared to my 400 f2.8 which is much larger and heavier.  The EF 400 is one of the L series lenses and is well built and I wouldn't hesitate to buy a well cared for used version.

 

Rodger

 

 

EOS 1DX M3, 1DX M2, 1DX, 5DS R, 1D M2, EOS 650 (film), many lenses, XF400 video
Forum Elite
Posts: 14,126
Registered: ‎12-07-2012

Re: lense extender for a Canon Rebel 3ti - 55-250 mm lense?

I don't have the mentioned lens to try but it may not even be possible to mount any of the Canon tel-cons to that lens..  Kenko makes one that will mount to your lens.  I suspect it will "work" but how well is the question.  At best it will be dark and slow. And by all means don't even think of or consider the 2x tel-con.

 

If you want a 400mm lens or equivalnet you should consider the ef 400m f5.6L. One of the best buys in a big telephoto.

EB
EOS 1DX and 1D Mk IV and several lenses!
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