1.4x Teleconverter; the right choice?

[ScottyP]

I have a crop-frame Canon (T3i) and only 2 lenses; the lovely EF-S 17-55 f2.8, and an EF-S 55-250 which I lucked into as a give-away after said lens was the only surviving piece of equipment after a friend's camera bag got swiped.

Obviously I already have a native 1.6x distance multiplier due to the camera body.

My question is, would the 1.4x TC be a good purchase? Primarily, I'd think it'd be used to extend the 55-250. It is already magnified x 1.6 to essentially a 400mm telephoto. But if I add in a 1.4 TC, would I be able to get acceptable bird shots losing IQ and a stop or two?

I guess a TC could also give my 17-55 a wee bit of extra reach, but, hmmm.

Note: I am not terribly serious about the long distance shooting, so I kind of hate to buy an expensive telephoto. On the other hand, I hate to buy even the teleconverter if it is going to be unacceptably bad results.

Thanks all.

 

[Loswr]

I presume you mean a 3rd party TC - the Canon one won't work with the EF-S 55-250mm, it's physically incompatible due to protruding elements on the TC. The Canon extenders only work with L primes of 135mm and longer, L zooms of 70mm and longer except the 70-300L, and also the MP-E 65 and TS-E lenses (although Canon doesn't actually list those last ones as compatible).


The 3rd party ones are a mixed bag, none optically as good as the Canon, the better ones that come close also report the aperture to the camera, so you'd lose AF on the 55-250 (need f/5.6 or faster), the ones that don't report will allow AF, but give you a horribly soft image.

Bottom line, I'd skip it...

 

[ScottyP]

Good point. Without AF, and with the other considerations, I'd probably do better to sell the little 250 lens, add that to the cost avoided by not buying a TC, and apply it towards a bigger zoom.

Or just skip it, which might be fine too.

Birds are rubbish when it comes to purchasing their portraits. Nearly impossible to cover the outlay.

 

[Marsu42]

the better ones that come close also report the aperture to the camera, so you'd lose AF

... unless you happen to have a little piece of tape with which you can cover some pins so af works again. The iq of the Kenko 1.4 is said to be good, but I didn't try it myself yet.

 

[rj79in]

the better ones that come close also report the aperture to the camera, so you'd lose AF

... unless you happen to have a little piece of tape with which you can cover some pins so af works again. The iq of the Kenko 1.4 is said to be good, but I didn't try it myself yet.

I've tried taping the pins but the AF speed is beyond belief ... SLOW! MF feels faster ;-)

 

[Loswr]

the better ones that come close also report the aperture to the camera, so you'd lose AF

... unless you happen to have a little piece of tape with which you can cover some pins so af works again. The iq of the Kenko 1.4 is said to be good, but I didn't try it myself yet.

I've tried taping the pins but the AF speed is beyond belief ... SLOW! MF feels faster ;-)

It is, indeed, slow. Under those circumstances (like when I use a 2x on my 100-400mm), I find that contrast detect AF (Live View) works decently, and it's not significantly slower than the pin-taping hack.

 

[Marsu42]

It is, indeed, slow. Under those circumstances (like when I use a 2x on my 100-400mm), I find that contrast detect AF (Live View) works decently, and it's not significantly slower than the pin-taping hack.

I didn't try taping myself yet, but I think about getting a Kenko 1.4 and would have to do this hack. Isn't the speed determined not only by aperture, but by absolute available light level, too? I plan to shoot 300mm*1.6*1.4 only in very bright daylight (When it rains I seek shelter, so much for weather sealing ).

 

[Mt Spokane Photography]

The best third party TC's (Kenko ) warn you that they do not work with EF-S lenses. I'm not sure if any of them will, that proturbance on the back of the lens will interfere. You can use a extension tube and lose infinity focus, which may make it useless for telephoto applications.

Check the specifications here:

http://www.thkphoto.com/kenko/products/teleplusdgxdg/telepluspro300af14xdgx/

 

[rj79in]

the better ones that come close also report the aperture to the camera, so you'd lose AF

... unless you happen to have a little piece of tape with which you can cover some pins so af works again. The iq of the Kenko 1.4 is said to be good, but I didn't try it myself yet.

I've tried taping the pins but the AF speed is beyond belief ... SLOW! MF feels faster ;-)

It is, indeed, slow. Under those circumstances (like when I use a 2x on my 100-400mm), I find that contrast detect AF (Live View) works decently, and it's not significantly slower than the pin-taping hack.

Does AF work in Live View even with the 2x attached? I've not tried this yet so I'm just curious.

 

[Mt Spokane Photography]

error in content removed.

 

[Random Orbits]

It is, indeed, slow. Under those circumstances (like when I use a 2x on my 100-400mm), I find that contrast detect AF (Live View) works decently, and it's not significantly slower than the pin-taping hack.

Is there a f/stop limit for which LiveView contrast detect will not work with lenses?

 

[Loswr]

Is there a f/stop limit for which LiveView contrast detect will not work with lenses?

No, the only limitation is that there be enough light and sufficient contrast where you're trying to focus. Conversely, phase detect AF depends on aperture and a certain (very low) threshold amount of light. For example, with an f/11 lens+TC (a 2-stop reduction in light from f/5.6), contrast detect AF (Live View) will work fine, phase detect will not. But, with an f/5.6 lens and a 6-stop ND filter on a dim day, phase detect AF will work, and contrast detect AF will likely fail.

 

[Mt Spokane Photography]

It is, indeed, slow. Under those circumstances (like when I use a 2x on my 100-400mm), I find that contrast detect AF (Live View) works decently, and it's not significantly slower than the pin-taping hack.

Is there a f/stop limit for which LiveView contrast detect will not work with lenses?

It will not attempt to AF with a slower than 5/5.6 lens. You can tape over the pins that convey the f stop setting to the camera, and it will then attempt to autofocus, but the results vary by individual body and lens, so just because mine worked is no guarantee yours will. I've experimented with many bodies, and found no sure formula to determine which works.

Another trick is to stack two TC's. The camera will only see the first one, so with a f/4 lens, you can use two TC's and sometimes it will autofocus in very good light.

Generally, its impractical and better if you use live view and manually focus. It certainly won't track birds in flight.

 

[Michael_pfh]

I can only judge on the use of TCs (1.4x and 2.0x) in combination with expensive telephoto lenses - they do perform great, especially the 1.4x only very slightly degrades the image quality.

 

[Loswr]

Is there a f/stop limit for which LiveView contrast detect will not work with lenses?

It will not attempt to AF with a slower than 5/5.6 lens.

The question was about an aperture limitation for contrast-detect AF (Live View AF). Are you suggesting that contrast-detect AF is limited to f/5.6 or faster lenses, the same as phase-detect AF?

 

[Mt Spokane Photography]

oops, caught me!

+1

 

[Random Orbits]

oops, caught me!

+1

No harm caused. I do have a question though: for which combinations of TCs and lenses were you able to achieve AF when it was not designed to (i.e. smaller than f/5.6)?

 

[Mt Spokane Photography]

oops, caught me!

+1

No harm caused. I do have a question though: for which combinations of TCs and lenses were you able to achieve AF when it was not designed to (i.e. smaller than f/5.6)?

I have tried it on a number of bodies and lenses over the years, and don't remember which combinations worked.

I recall my 1D MK III working with a 70-200mm f/4 and two TC's(1.4 and 2X), which made it a f/11 combination.

I also recall my 40D working with a Canon 400mm f/5.6L plus a non reporting TC, both 1.4X and 2X worked. I tried it on a XTi and it didn't.

I tried some combinations on my 5D MK II as well, but don't remember the results. Its hard to find from EXIF, since only the 1.4X TC shows up, so I named some of the files with both TC's so I could find them.


Here is the 1D MK III image with two TC's (F/11). Remember, its mostly a experiment, its not a practical image capturing situation, you can only do it with very good light.