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

CyberDyneSystems wrote in post #4309808
Foxbat, MkII version I assume?

Yes, sorry for not being clear. It's the Canon TC 1.4x Mk2. Post edited.

Does the Kenko 2.0 MC7 report correct aperture to the camera?

nrowensby wrote in post #4320793
Does the Kenko 2.0 MC7 report correct aperture to the camera?

I just found this description on the web, "The MC 7 converter has genuine Gate Array IC (Integrated Circuitry). It means that the converter's unique circuitry maintains signal integrity between the camera body and lens. These converters are designed to electronically operate the same way an original manufacturer's converter would.Full AF operation with Teleplus MC7 is possible with camera lenses with open aperture of F/2.8 or brighter. "

Judging from that description, the MC7 does report its presence to the body, as the body sees the native f/2.8 lens with the MC7 as f/5.6, which is what is needed for autofocus on lesser (non-1D) Canon bodies.

nrowensby wrote in post #4320793
Does the Kenko 2.0 MC7 report correct aperture to the camera?

According to this photo, it doesn't. (Notice the photo is of a Canon mount TC).
To report the aperture the TC has to say to the lens if it is here and if it is 1.4X or 2X. The TC tells it to the lens through three pins dedicated to the TC information. You can see the pinshere marked in red.

Wilt wrote in post #4320972
I just found this description on the web, "The MC 7 converter has genuine Gate Array IC (Integrated Circuitry). It means that the converter's unique circuitry maintains signal integrity between the camera body and lens.
Judging from that description, the MC7 does report its presence to the body, as the body sees the native f/2.8 lens with the MC7 as f/5.6, which is what is needed for autofocus on lesser (non-1D) Canon bodies.

It is possible that if you put a 3X TC between a, say, 50mm /f1.4a nd the camera, the TC may intercept the identification signal and change 50mm for 150mm and so on.

But I´m afraid that the gate array is here only to restore the electrical signals to the standard values. The signals between the camera and the lens are the power (VBAT2=6Volts), CPU voltage (VDD=5.5V) and the data and clock wich I'm not sure, but say they should be at high=5V or low=0. The truth is that high is something over, say 3V and low something below.

The idea is that the electrical path from the chips through the connectors to the lens is long, and has its resistance. So the electrical signals may drop from it's value. At the chip they are maybe 4.5V for high and 1V for low, but at the lens connector they drop to 4V for high and 1.5V for low.
I think that the gate array restores the signal again to 4.5 and 1.5V again. But I don't see the point in restoring a signal with almost negligible benefit. Of course it has its power consumption also (almost negligible also).

Pablo,
What does not ring true is the statement on the website, "Full AF operation with Teleplus MC7 is possible with camera lenses with open aperture of F/2.8 or brighter. " If it did NOT report the presence of the MC7 DG, the body would simply think that there is less available light in the scene, rather than not focusing at all!

OTOH, I just found this message on POTN

https://photography-on-the.net …hp?p=1814426&po​stcount=50

and it states that the 400 f/5.6 with the 2X MC7 DG does focus, which would not be true if it was reporting due to the DG. So that seems to point to bad information on the website about the DG rating.

Just picked up a Kenko 1.5x DG today from Henry's superstore in Toronto for $130. Put it on the 70-200 f4 L and it works a treat, AF doesn't hunt much at all even shooting indoors with decent lighting. Doesn't register in the EXIF or on the camera either and I can't visibly see any terrible loss of quality when using it, going to take some more test shots tomorrow and also go to Henry's and test it out on a 100-400 L as that is my next lens purchase.

Wilt wrote in post #4330076
Pablo,
What does not ring true is the statement on the website, "Full AF operation with Teleplus MC7 is possible with camera lenses with open aperture of F/2.8 or brighter. " If it did NOT report the presence of the MC7 DG, the body would simply think that there is less available light in the scene, rather than not focusing at all!

The AF sensors is built with a couple of lenses located at 5.1 degrees from the axis, one above and one below. To get AF, there must be enough light. Also, light must come from those directions. Also, the lens should know the resulting focal length and aperture, and report to the camera, and work with different tables for the AF algorithms.
Mr. Canon has chosen to sell a high quality AF instead of a AF that may work with I-don't-know-what-combination-of-TC-and-lens if you're lucky. So they specify f/5.6 as the worst f/stop wich allows AF (though sometimes it works at f/8, and you report that it works at f/11 in a 20D).
They also has developed a method to report to the camera the presence of a TC, and to report the focal length and aperture to the camera when a TC is used, and this method turns off automatically the AF when working with slower than f/5.6 lenses.
Only a f/5.6 or faster lens may fulfill all the requirements (the AF lenses will receive light through all their surface and so on). If we try to work with a equivalent combo of more than f/5.6, or with a non-reporting TC, we are not working as Mr. Canon thought, and it may or it may not AF. This is not consistent, and may give an impression of a bad product.
Fortunately, we have the possibility of fooling the TC reporting method.

Wilt wrote in post #4330076
OTOH, I just found this message on POTN
https://photography-on-the.net …hp?p=1814426&po​stcount=50
and it states that the 400 f/5.6 with the 2X MC7 DG does focus, which would not be true if it was reporting due to the DG. So that seems to point to bad information on the website about the DG rating.

To get quality you have to get consistent results. Will a resultant f/11 lens AF with a Canon camera? Maybe with the 20D. Maybe only with Mr. Big Hands' 20D. Definitely not with my 400D. However, I think it's worth a try.

smcclelland wrote in post #4330980
Just picked up a Kenko 1.5x DG today from Henry's superstore in Toronto for $130. Put it on the 70-200 f4 L and it works a treat, AF doesn't hunt much at all even shooting indoors with decent lighting. Doesn't register in the EXIF or on the camera either and I can't visibly see any terrible loss of quality when using it, going to take some more test shots tomorrow and also go to Henry's and test it out on a 100-400 L as that is my next lens purchase.

I'd like to know the results with the 100-400 IS. People are reporting that it doesn't work well with it.

I thought long & hard about the 100-400, & I've used a borrowed one & liked it. Then I decided that I'd get more out of a 70-200 f/2.8 & a 2X TC.
Still need to buy the TC. Then we'll see how that works out.

I bought the Kenko 1.5x and it works wonders for me. I first used it with the 30D and 300/f4 non-IS and it just snapped to focus, no hunting or anything. Then I stacked it behind my Sigma 1.4x, same thing, no hesitation, snap to focus and the IQ was very good, although not as sharp as without, of course, but fixable in CS2.

I now have the 1D Classic and all works phenominally well, with double stacked TC's, it keeps auto focus and it focuses very fast, with no hunting. So I recommended the Kenko 1.5x to someone with a 100-400 and 40D and they say it doesn't work with it. Actually, a couple someones, one with a 30D and 400L Prime, and they had problems too. Go figure.

Well the tests were confirmed today, AF works just fine with the 100-400 on an XTi with the Kenko 1.5x. I haven't used the 100-400 before so my initial reaction was the AF was decent, though not as speedy as the 70-200 f4 (a given). It didn't seem to hunt that much and I was shooting indoors inside a mall as well as in the store under the fluorescent light. A few test shots outside under overcast conditions showed the same result with AF not hunting at all and getting consistent locks on tracking cars etc. Time to invest in a 100-400, see if there's any kicking about on the forums these days

Can i stack two 1.4TCs on a 70-200f2.8 IS L attached to a 40D or 400D?? Will they physicaly fit and will they AF?

NSWESP wrote in post #4342974
Can i stack two 1.4TCs on a 70-200f2.8 IS L attached to a 40D or 400D?? Will they physicaly fit and will they AF?

I think one of them must be a non Canon type to do this. I do it with my 400mm f5.6 with a Kenko pro nearest the camera and a Canon fitted into the Kenko.

Thanks so my options are:
OPTION 1 (Possibly wont work):
2x Canon 1.4 TCs
OPTION 2:
1x Canon 1.4 TC
1x Canon 2 TC
OPTION 3:
2x Kenko Pro 300DG 1.4 TCs
OPTION 4:
1x Kenko Pro 300DG 1.4 TC
1x Kenko Pro 300DG 2 TC

Any suggestions on which option to go for?

NSWESP wrote in post #4343035
Thanks so my options are:
OPTION 1 (Possibly wont work):
2x Canon 1.4 TCs
OPTION 2:
1x Canon 1.4 TC
1x Canon 2 TC
OPTION 3:
2x Kenko Pro 300DG 1.4 TCs
OPTION 4:
1x Kenko Pro 300DG 1.4 TC
1x Kenko Pro 300DG 2 TC

Any suggestions on which option to go for?

Hi, NSWESP,
I expect more quality with a 2X TC than stacking two 1.4X TCs.
And about the brand, I have found a comparison of the Canon 1.4X and the non-SP Tamron 1.4X, and a comparison of the 2X Canon and Tamron SP.
Note that the 2nd comparison is against the Tamron SP 2X TC, but you can find posts in this same thread telling that the Tamron SP are a rebranded copy of the Kenko Pro. I'd go for the option 4.