Has anyone tried this combo? Just this weekend I tried stacking my canon 1.4 plus my Keniko 1.4 and the AF hunts like a ban-chi. I have successfully used this combo with my 1dmk4. Any ideas or similar experiences would be gratefully appreciated?
FYI: I was shooting sports servo AF case mode 4 with tracking sensitivity turned down to -2 the slowest setting.
Also the lens works fine with either TC by its self.

Andy

it use to work, but it may not since the FW updated to allow f/8 AF...

ifxbonz wrote:
Has anyone tried this combo? Just this weekend I tried stacking my canon 1.4 plus my Keniko 1.4 and the AF hunts like a ban-chi. I have successfully used this combo with my 1dmk4. Any ideas or similar experiences would be gratefully appreciated?
FYI: I was shooting sports servo AF case mode 4 with tracking sensitivity turned down to -2 the slowest setting.
Also the lens works fine with either TC by its self.

Andy

Have you updated the firmware? It should work. I can try tomorrow.

P.S. shouldn't that be "banshee"? Not that "banchi" doesn't exist.

banchi nipple, http://www.urbandictionary.com/define.php?term=banchi
banchi turtle, http://onepiece.wikia.com/wiki/Banchi

big country wrote:
it use to work, but it may not since the FW updated to allow f/8 AF...

Surely the FW update would mean it's more likely to work, not less

Canon's own TC's unfortunately don't physically stack together - at least, the 1.4X III and the 2.0X III.

Db

ifxbonz wrote:
Has anyone tried this combo? Just this weekend I tried stacking my canon 1.4 plus my Keniko 1.4 and the AF hunts like a ban-chi. I have successfully used this combo with my 1dmk4. Any ideas or similar experiences would be gratefully appreciated?
FYI: I was shooting sports servo AF case mode 4 with tracking sensitivity turned down to -2 the slowest setting.
Also the lens works fine with either TC by its self.

Andy
Forgot to add that this was with my 200 f2. And the firmware is up to date.

Andy

Andy,

The issue of 'banshee hunting' will occur anytime you use two tele-extenders, because the camera doesn't know how to compensate for the extra glass in the mix.

Basically, what the camera is doing, is over driving the lens to the point of focus it 'thinks' it needs to be based on the reading it gets from the extra three pins found on extenders. Contacts on two of the pins means it has a 1.4x attached and therefore the lens drive algorithm is adjusted for that. With the other two contacts (one common ground), then the camera 'sees' a 2.0x attached and compensates the lens drive accordingly.

With extenders on, the lens doesn't need to travel as much for focus with the extra reach (glass). However, when you add another extender into the equation, the camera doesn't register it, (it only calculates for one extender) and the result is the lens over driving to the intended focus expectation.

What you probably hear/see is focus drive past where you need to be, then backwards past again, but slightly less so, then past, again less, repeat (alot) until it finally settles on focus.

The same thing can be achieved by simply taping over the extra three pins on the extender, so the camera doesn't register it at all, and the lens will go bonkers trying to hit the mark.

So the only way to get close to getting around it is to re-wire the pin outs on the extender so that it thinks you have a 2.0x extender on it, which won't solve the problem (.04 off actual 2.0), but it may make it alot quicker to finally achieve focus. (Dunno on this one, I never tried it in my experimentations many years ago with Mk1, 200/1.8 and Canon 1.4x + 2.0x)

Hammy wrote:
Andy,

The issue of 'banshee hunting' will occur anytime you use two tele-extenders, because the camera doesn't know how to compensate for the extra glass in the mix.

Basically, what the camera is doing, is over driving the lens to the point of focus it 'thinks' it needs to be based on the reading it gets from the extra three pins found on extenders. Contacts on two of the pins means it has a 1.4x attached and therefore the lens drive algorithm is adjusted for that. With the other two contacts (one common ground), then the camera 'sees' a 2.0x attached and compensates the lens drive accordingly.

With extenders on, the lens doesn't need to travel as much for focus with the extra reach (glass). However, when you add another extender into the equation, the camera doesn't register it, (it only calculates for one extender) and the result is the lens over driving to the intended focus expectation.

What you probably hear/see is focus drive past where you need to be, then backwards past again, but slightly less so, then past, again less, repeat (alot) until it finally settles on focus.


The same thing can be achieved by simply taping over the extra three pins on the extender, so the camera doesn't register it at all, and the lens will go bonkers trying to hit the mark.

So the only way to get close to getting around it is to re-wire the pin outs on the extender so that it thinks you have a 2.0x extender on it, which won't solve the problem (.04 off actual 2.0), but it may make it alot quicker to finally achieve focus. (Dunno on this one, I never tried it in my experimentations many years ago with Mk1, 200/1.8 and Canon 1.4x + 2.0x)

Hey Hammy,
Thanks for the reply, but the same TC combo works fine on my 400mm 2.8 IS on the 1Dmk4 or 1Dx, but when attached to the 200mm 2.0 plus the 2 / 1.4 TC's the hunting is crazy unstable.

It pumps in and out rapidly, and solid on the 400mm.

The SN of my 200mm f2 is on the firmware update list from canon but only with the 5dkmk3 combo.
lens is now scheduled for firmware repair with canon so we will see.

Andy

Andy,

My guess is that the wide open aperture of the f/2 lens (like my 1.8 variant) has alot more glass to move - or at least move it farther due to the optics - compared to a longer piece of glass at f/2.8? Again a guess.

I just know that my testing 10 years ago resulted in the same results.

But then again, maybe Canon is capable of tayloring to their customers with firmware that does look for multiple extenders now-a-days... let us know how the update goes.

Lens comes back today. stay tuned.

Andy

Use zone AF mode.