a ????? for canon experts

[terryger]

why does canon make extenders that will not communicate with the af on their own lenses. why do you have to block the communucation to get the af to work?

the 1.4 will only work the af on a 100-400 by blocking the pins on the extender and this does not work at all on the 2x. i would assume it is the same on the 70-200 as the af works their with the pins blocked also.

imagine all the folks that think their 1.4 and 2x are canon junk due to this fact.:idea:
thanx!

[EOSThree]

Nothing is free, a t-con may seem like a cheap way to extend your range, but when the aperture goes smaller than f/5.6 Canon has decided that there isn't enough light for AF and the AF is disabled. Blocking the pins stops this from happening, sometimes you can focus, sometimes you can't. A t-con was never meant as a great solution to more range, it's a compromise at best.

[Asylum Steve]

why does canon make extenders that will not communicate with the af on their own lenses. why do you have to block the communucation to get the af to work?

Well, I'm not sure I have the answer, but the two lenses you mention are both zooms. I've used extenders on and off throughout my career, and I've always thought of them as accessories for prime lenses.

IMO, using them with zooms is a bit of a compromise, and as such you sometimes have to expect to lose certain camera or lens features for them to work...

[Asylum Steve]

when the aperture goes smaller than f/5.6 Canon has decided that there isn't enough light for AF and the AF is disabled...

This makes sense, and is probably a better answer than mine. So, it would seem it's more a question of lens speed...

[terryger]

please don't take this as a personal attack but i find those reasonings pretty borderline

"when the aperture goes smaller than f/5.6 Canon has decided that there isn't enough light for AF and the AF is disabled."

so why not disable the af all togeher or why bother having aperture settings smaller than f5.6?

when i buy a $2-250 piece of glass, for whatever reason i choose to use it , i expect a lot more out of it than "lets tape it so it will work". don't you?

i have $5500 worth of L lenses so "Nothing is free, a t-con may seem like a cheap way to extend your range" is a photographic dog that won't hunt in this pasture!

the 1.4 and 2x are photographic accessories and as such, especially at the price they command, i believe it resonable that they work without tape.

"I've always thought of them as accessories for prime lenses"

"IMO, using them with zooms is a bit of a compromise,"

hmmm, not sure why you would think that. what would be your reasoning?

"sometimes you can focus, sometimes you can't."

no, you can always focus though it is a tad slower and searches a little in very low light but all af's search in low light anyway. it is the nature of their af mechanism. "So, it would seem it's more a question of lens speed..."

well that would be the case if it was just the 100-400 but with the the 2.8 you're back to a dog that won't hunt again. the af works just fine in the 2.8 with the pins taped which means they are useless there also.

"A t-con was never meant as a great solution to more range, it's a compromise at best."

actually that is exactly what it was made for. maybe not great but a soultion none the less. thus the name "teleconverter".

now, it was not meant as a replacement for another 100 mm, granted, but it was a sloution for more range. and not cheap either. and i can get more range.



i don't call "not working" a compromise.

you guys all gave it your best shot but i am interested in more ideas cause "shoddy performance" has not been knocked off the list yet!

i know it works if the pins are taped. think of how many are trashed because that fact is withheld by canon, the people responsibile for it in the first place.

[mjs1973]

What body are you using this with? I just looked up the 1.4TC at B&H and they have a compatibility chart that shows just what this TC will work with. With the 100-400mm lens the AF will work, but only with the EOS 1v and the EOS 3 bodies, and only with the center AF point.

The compatibility chart for the 2xTX shows that AF wont work with the 100-400mm lens.

This doesn't answer the question why, but is does show that the info is available to the consumer to show us just what these products will and wont work with.

[Lionheart]

why does canon make extenders that will not communicate with the af on their own lenses. why do you have to block the communucation to get the af to work?

the 1.4 will only work the af on a 100-400 by blocking the pins on the extender and this does not work at all on the 2x. i would assume it is the same on the 70-200 as the af works their with the pins blocked also.

imagine all the folks that think their 1.4 and 2x are canon junk due to this fact.:idea:
thanx!

I'm not sure what you mean by"will not communicate with the af on their own lenses." The Canon 1.4x and 2x TC's are designed with very specific lenses in mind, and the 100-400 is one of them. AF might be sketchy on that particular zoom since the loss of light is disastrous, especially with the 2x TC, but it does work to some degree. Which 70-200 lens are talking about? If you have the F4 version, then yes, the AF might be a problem since your max aperture drops to f5.6 and f8 respectively, and any lens with a max aperture of f5.6 can struggle with AF at less than daylight environments, and at f8 forget it. If on the other hand, you have the f2.8 version, then it should work just fine with both TC's. I have both TC's, have had the 100-400 IS, and also the f2.8L version of the 70-200, and have not had any problems (I shoot with 1D, 1D mk II, 10D). I've even stacked the 1.4 and 2x with the 100-400 and 70-200 just for grins and they've worked-barely :-), but they did AF and lock at least a third of the time. You may want to send your TC's and lenses into a Canon repair center for checking if they're not behaving as advertised. Good luck.

[EOSThree]

Canon makes no bones about it, the specs specifically say fixed focal length lenses longer than 135mm with exceptions, and a few select zoom lenses. It also mentions the AF problems you'll have with apertures of f/4 or more. What's the trouble? Canon has been totally up front. If you don't want your t-con to have these limitations, don't buy a Canon, it's really pretty simple. I'm with Steve, I have never considered using one on a lens of less than 200mm, or on a zoom lens. I have focal lengths to cover from 17mm to 300mm and never consider using my t-con(Tamron pro) on anything other than my 300mm. Why would I, no matter how good it is, it's still another piece of glass in between my sensor and my subject and it takes a stop of light away, I won't even consider a 2x, it just takes away too much light, and with that AF will be compromised. Do I expect my 300mm+1.4x to perform like a 400mm f/5.6, heck no, it's adequate, and will suffice until I can afford a 400mm. Canon has never intended them to work the way you are expecting them to work, they are quite up front about it. It's a cheap compromise, if you don't like the way it works pony up the money for the actual focal length...I'll say it again: nothing is free, that photographic dog does hunt.

From Canon USA:
Extender EF 1.4x II
Lens Extender
This tele extender can be used with fixed focal length lenses 135mm and longer (except the 135mm f/2.8 Softfocus lens), and the EF 70-200 f/2.8L, 70-200 f/2.8L IS, 70-200 f/4.0L, and 100-400 f/4.5-5.6L IS zoom lenses. Superb optically, it preserves the image quality of the lens it's mounted to and multiplies its focal length 1.4x. Effective aperture is reduced by one f-stop; autofocus is possible on any EOS camera when combined with a lens having an f/4 or faster maximum aperture. The new version II maintains the outstanding optics of the previous version, and adds enhanced weather-resistant construction, and improved anti-reflective surfaces in the barrel.

Extender EF 2x II
Lens Extender
This extender has been re-designed optically and offers excellent performance with compatible EF lenses (same as the Extender EF 1.4x II). Features a new seven-element design, and same weather-resistant design and anti-reflection internal construction as the new EF 1.4x II. The EF 2x II doubles the focal length of any lens it's mounted to, and reduces its effective aperture by two stops. With the EF 2x II, AF is possible with any EOS body if the lens has an f/2.8 or faster maximum aperture, and compatible Image Stabilization lenses maintain the IS feature when used with any current EOS camera.

[terryger]

"This tele extender can be used with fixed focal length lenses 135mm and longer (except the 135mm f/2.8 Softfocus lens), and the EF 70-200 f/2.8L, 70-200 f/2.8L IS, 70-200 f/4.0L, and 100-400 f/4.5-5.6L IS zoom lenses. Superb optically, it preserves the image quality of the lens it's mounted to and multiplies its focal length 1.4x. Effective aperture is reduced by one f-stop; autofocus is possible on any EOS camera when combined with a lens having an f/4 or faster maximum aperture.


i believe what we have here is a failure to communicate. both by canon and by you and i.

since you are unfamiliar with the canon 1.4 ("my t-con(Tamron pro)" ) it seems you are just trying to run a canon statement you do not know to be truthful. i prefer canon over aftermarket for many reasons.

i stated clearly what lenses i was using the 1.4 ext on and i never mentioned "less than 200mm" so that again is your invention.


in the canon satement above it specifically lists both lenses i use and being included in the "may be used" list but then says it cannot be sued on the 100-400 if auto focus is desired.

back to my original questions, if that is the case, why bother listing the 100-400? what use is a 1.4 ext with no auto focus?

and though not needed on my 2.8 why does it still work with the pins taped?

i do not expect my 100-400 to work like a 560, which it in effect it is with the 1.4, but i certainly do expect "Superb optically, it preserves the image quality of the lens it's mounted to and multiplies its focal length 1.4x. " from it which canon promises in writing.

i use a pair of 20 d bodies.

the 100-400 will not autofocus ion this body without taping pins off.

thanx for your input.

i guess it is just fortunate for me that i have learned how to use my 1.4 despite the canon roadblocks!

[EOSThree]

Sorry I read more into your statements than was actually there.

"Superb optically, it preserves the image quality of the lens it's mounted to and multiplies its focal length 1.4x. " from it which canon promises in writing."

AF has nothing to do with image quality, image quality is the ability of the lens to resolve a certain amount of data, even if it's totally Oof it still has the potential to resolve that amount of data, it's up to you the photographer to make sure that the image is in focus whether you are using AF or manual focus. AF is a convenience, a convenience that many take for granted now, the t-con compromises that convenience. Canon even says it compromises the AF, even so, the IQ when focused manually is still preserved. All cameras were manual focus about 20 years ago, somehow people still managed to get the shot and have superb IQ.

"since you are unfamiliar with the canon 1.4 ("my t-con(Tamron pro)" ) "
There you go putting words in my mouth, I am familiar with the Canon and chose the Tamron over the Canon, in my tests I actually had better image quality with it than with the Canon, and it cost a whole bunch less.

"what use is a 1.4 ext with no auto focus?"
Ooo, I know, let's see, it will increase your focal length by .4 times. That's what a teleconverter does. AF may or may not work.

I agree with you that the Canon t-cons are a little limited in their use, but that is generally the nature of a t-con. I have never considered a t-con to be anything but an accessory, I have never expected much from them.

[ekstasis16]

Good grief, what's with the all the confrontation? Save it for Canon if you have a beef with them.

Yes, the teleconverters are not God's gift to photography. If they were the perfect solution then most of us would have no reason to go drop a couple thousand on a big ol' 400 or 500 lens. The reason these teleconverters function as they do is because Canon has a legitimate business interest in having us continue to purchase these more expensive lenses.

You pretty much have one option if you want to use a 1.4x TC with the 100-400 and keep the autofocus: buy a 1D series body, which can autofocus down to f/8. Otherwise, buy a 300mm 2.8L lens and slap a 2x TC on it to give you 600mm at f/5.6 which will work on a 20D.

Neither option is cheap. Its the price we pay for quality and high-tech gear.

[Loupey]

I have a theory: having been around, working with, and managed engineers/programmers for nearly 2 decades, I can say that they, in general, are a pretty conservative bunch. I surmise that the developers have intentionally programmed the AF to NOT work when the combined max aperture is less than f/5.6 due solely to focus reliability issues. Better to simply turn off the feature instead of getting complaints that it works here and there but not everywhere.

That would explain why both the 100-400 and the 70-200 still work when the contacts are taped. The camera no longer has the lens info which would normally shut down the AF subroutine.

Frankly, I'm surprised that the developers even allow the AF to engage without the lens detail. I would have disabled both the AF and IS if no such info was present.

I use my 2xTC with my 300mm. There is a purpose and place for these things. Traveling light, traveling cheap, and traveling small are three. No, I don't expect it to perform like a 600mm f/4L. But then, neither will a 500mm f/4L