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PostPosted: Sun Nov 21, 2010 10:17 am 

I have a canon 55-250 IS telephoto lens. I saw some adapter lenses on ebay with a 3.5x conversion factor. Which you fit onto the front of your lens to multiply its focal length. My second option is a seperate rokinon or opteka 500mm mirror lens. Which will give better image quality when used on my 550d ?

Please keep in mind that i mostly use my camera only for video. And ive heard that lens quality hits on the image quality are not as obvious on video as they are in images that are subject to keen scrutiny.

Id like to know which would be a better option.


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PostPosted: Sun Nov 21, 2010 2:16 pm 

Joined: Mon Jan 18, 2010 3:52 pm
Posts: 2182
Location: The Netherlands
Most mirrorlenses dont have AF, and with planes it could be handy.
The bokeh of the mirrorlenses are not that great too, Id go for a tele-extender.


Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies

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PostPosted: Sun Nov 21, 2010 2:25 pm 
What on earth are you shooting that makes you think you need a 1400mm equivalent lens? :shock:

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PostPosted: Sun Nov 21, 2010 4:30 pm 

Joined: Mon Sep 06, 2010 11:30 am
Posts: 212
Location: Phnom Penh
1400mm :shock:
you really know how to shoot a top secret photo, nice. :wink:

Canon EOS 7D + Red Canon IXUS 300HS.
Canon EF 17-40mm f/4L,Canon EF 100mm F/2.8L IS USM.
Sigma 70-200mm F/2.8 APO EX DG OS HSM, Sigma 50mm F/1.4 HSM
Canon Speedlite 480EX II + Tripod+ B+W MRC (2x77+67), hoya HD UV (77) B+W MRC 77mm(CPL slim+10 ND).

 Post subject:
PostPosted: Mon Nov 22, 2010 5:23 am 
Hi Guys.

1400mm ?? Ok i guess your taking into consideration the 1.6 crop factor am i right ? :).

I was looking at something that gives me between 500-800mm. Maybe for some wildlife shots. Never assume why one would need such a long range hmmm. There are some subjects, such as waterfalls etc which are far away and i wish i had more zoom range on those subjects.

Ruben > If i put a 2x extender (you meant an extension tube right ?) on my 55-250 IS will the sharpness quality take a hit, also will AF and Aperture control etc work ?


 Post subject:
PostPosted: Mon Nov 22, 2010 7:41 am 
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Joined: Sun May 25, 2008 12:48 pm
Posts: 8087
Location: UK
A 2x extender or teleconverter is not an extension tube. If I can find one that fits that is, as many have a front protrusion, and EF-S lenses have a rear protrusion so they likely many wont. Probably rules out Canon and Sigma ones, might be ok on Kenko generic (non-Pro) ones. Sharpness will take a hit. Phase AF wont work. Contrast AF in live view might. Aperture should be ok.

Canon DSLRs: 7D2, 7D1, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 85/1.8, 135/2+SF, 70-300L, 100-400L, 100L, MP-E 65, EF-S 10-18, 15-85
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 50/1.4A, 150 macro, 120-300 f/2.8 OS
Compacts: Sony HX9V, Fuji X100.

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