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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 27 Sep 2005 (Tuesday) 12:45
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STICKY: -=FAQ=- Teleconverter/T-Con Tele extender Discussion

 
sploo
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Jun 15, 2013 16:34 |  #616

Richard N wrote in post #16034092 (external link)
Both will cost 2 stops of light, the 2x1.4 option offers 40% more focal length but costs a fair bit more.

I'm afraid it's the same in terms of focal length:

200mm + 2x TC = 200 * 2 = 400mm
200mm + 1.4x TC + 1.4x TC = 200 * 1.4 * 1.4 = 400mm (well, close, anyway*)

I suspect two 1.4x TCs will give worse image quality than a single 2x.

* If the 1.4x TC is a true sqrt(2) multiplier then it'll be exactly 200mm * 1.414 * 1.414 = 400mm


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Richard ­ N
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Jun 15, 2013 16:51 |  #617

sploo wrote in post #16034119 (external link)
I'm afraid it's the same in terms of focal length:

200mm + 2x TC = 200 * 2 = 400mm
200mm + 1.4x TC + 1.4x TC = 200 * 1.4 * 1.4 = 400mm (well, close, anyway*)

I suspect two 1.4x TCs will give worse image quality than a single 2x.

* If the 1.4x TC is a true sqrt(2) multiplier then it'll be exactly 200mm * 1.414 * 1.414 = 400mm

Okay... my bad math. I thought you could add the TCs together and then multiply the focal length of your lens. I got it all wrong.

Thanks for the quick answer.


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pwm2
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Jun 16, 2013 08:27 |  #618

Richard N wrote in post #16034092 (external link)
Would I be giving up a substantial amount of IQ using two Sigma APO EX 1.4x versus a single 2.0x?

Both will cost 2 stops of light, the 2x1.4 option offers 40% more focal length but costs a fair bit more.

Sounds like you compute 1.4+1.4 aka 2x1.4 = 2.8 as giving larger magnification than a 2x TC.

But that is incorrectly computed. Stacking several TC is a multiplicative and not additive operation.

The correct computation is 1.4x1.4 = 1.96 i.e. the same magnification as a 2x TC.

That is also why two 1.4x TC changes amount of light the same as a single 2x TC.


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rogertb
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Jul 08, 2013 05:02 |  #619

Hi chaps - I did a search but with little luck so forgive me if this has been covered. Is the Canon x2 MkI any good or should I save some more money and buy the Mk II ?

Best Roger


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Pax2You
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Jul 08, 2013 08:57 |  #620

The 2x Mk II was designed to eliminate internal reflections, has weather sealing, and had a redesigned element structure. I've not used the Mk I so I can't say how they compare in the field, but I can say I have been very impressed with the MK II paired with Canon glass.


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rogertb
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Jul 08, 2013 09:00 |  #621

Thanks Pax2you - if it's cheap enough I might give it a try ... best Roger


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hollis_f
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Jul 08, 2013 10:27 |  #622

rogertb wrote in post #16100971 (external link)
Hi chaps - I did a search but with little luck so forgive me if this has been covered. Is the Canon x2 MkI any good or should I save some more money and buy the Mk II ?

If you're planning on using it with the 400 f5.8 then I'd buy the cheapest you can find. That way you lose less money when you realise that an 800mm lens with no IS, manual focus only and a wonderfully dark f11 maximum aperture isn't really worth what you paid for the TC.


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rogertb
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Jul 08, 2013 11:02 |  #623

Very good point and well put Hollis_f - yep, I've got a 1.4 on the 400mm and it works well but, almost for a bit of fun, thought I'd try the 2x. One of the good things about auction sites is that if you buy a used lens there's a pretty good chance of getting most of your money back when you find it's really not working as well as you'd hoped.

My current lens collection is based, pretty much, on trial and error, buying used glass, testing it for a while and, sometimes, selling it on.

On that basis I'm not sure why I'm even considering the Mk I .... answered my own question really .... though I don't have the funds for a Mk III ... sorry I'm drivelling on now and will end.

Best Roger


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markisclueless
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Jul 24, 2013 03:05 |  #624

hollis_f wrote in post #16101616 (external link)
If you're planning on using it with the 400 f5.8 then I'd buy the cheapest you can find. That way you lose less money when you realise that an 800mm lens with no IS, manual focus only and a wonderfully dark f11 maximum aperture isn't really worth what you paid for the TC.

Hi Frank, I have a 400mm 5.6L (and Canon 600D body) and want to try Canon 1.4x II with it - ie f8 - I know I will loose AF and with non IS am I wasting my time (and money) ?


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sploo
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Jul 25, 2013 07:32 |  #625

markisclueless wrote in post #16148879 (external link)
Hi Frank, I have a 400mm 5.6L (and Canon 600D body) and want to try Canon 1.4x II with it - ie f8 - I know I will loose AF and with non IS am I wasting my time (and money) ?

Totally depends on what you're shooting. DOF at 560mm at f8 with a subject at 10m will be less at 10cm, so if it's moving you may struggle with the lack of AF.

I suspect that (certainly stopped down to f11) the quality will be decent. At f11, and a 20m subject distance you'll have over 50cm of DOF, and for a largish (~40cm+) bird gliding above you it might work quite well. That's assuming there's enough light for a decent shutter speed, of course.


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blair1955
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Aug 04, 2013 15:18 |  #626

This may have been asked already but I want a 1.4 converter that will work with my Tamron 70-300 f/4-5.6 Di VC lens and don’t know which brand to get. Also how much weight can the mount on my 60D take? I don’t want to over stress it.




  
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sploo
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Aug 04, 2013 16:32 |  #627

blair1955 wrote in post #16180701 (external link)
This may have been asked already but I want a 1.4 converter that will work with my Tamron 70-300 f/4-5.6 Di VC lens and don’t know which brand to get. Also how much weight can the mount on my 60D take? I don’t want to over stress it.

Weight wise, I'd think you'd be absolutely fine with the mount - a 1.4x TC isn't that big, and I don't believe there's any reason you couldn't put one of the monster telephoto primes on the 60D. I believe the Canon 70-200 f4 IS L is about the same weight as the Tammy, and my other half happily uses that + a 1.4x TC with a 60D.

I suspect you may have to avoid the Canon ones - certainly the version III models have a protrusion, and it won't fit into the back of the Tammy.

TBH though, you may want to consider if it's the right thing to do; the Tammy is a great lens for the money, but it's not stellar at the long end, and a TC will only make that worse. With a 1.4x TC you'll be at f8 at 300mm for AF (which means manual focussing on the 60D - unless you trick the camera into thinking the TC isn't present, but it's still unlikely to work well). You'd probably also want to stop down once more to help the quality, which means you'd need to shoot at f11. In short - I'd definitely recommend borrowing or renting a TC first, as I have a feeling the results on the Tammy won't be worth the purchase cost of a decent TC.


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blair1955
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Aug 04, 2013 17:45 |  #628

sploo thanks I did look into rental of a Tamron TC and with insurance & shipping for 5 days its US$50 or 1/3 the cost to buy one. maybe I'm in the wrong line of work...




  
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sploo
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Aug 05, 2013 02:24 |  #629

blair1955 wrote in post #16181068 (external link)
sploo thanks I did look into rental of a Tamron TC and with insurance & shipping for 5 days its US$50 or 1/3 the cost to buy one. maybe I'm in the wrong line of work...

Yea - rental prices aren't always directly related to the cost of the item; high value kit that's popular, but robust, can be a good choice for rental as it's relatively low effort for the renter to maintain, but makes a good return. For cheaper items the savings aren't so much.

Could you save some cash by doing a shorter rental? 2-3 days (if you can get a good chunk of time over those days) should be enough to test it thoroughly.

In general though, the advice is: high quality prime + TC = ok, a small number of high quality zooms + TC = just about ok, everything else = save your cash and don't bother buying a TC.


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tdodd
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Aug 05, 2013 02:51 |  #630

Sploo speaks the truth. No point magnifying a mediocre image further, so that it just looks even worse, and losing a stop of light and AF to do it.




  
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-=FAQ=- Teleconverter/T-Con Tele extender Discussion
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