Kenko teleconverter questions

[miah]

1. How do teleconverters affect a lens's Minimum Focus Distance?

2. When I AFMA a lens with FoCal, it gives me a figure (+3 or -2, etc.) that I manually dial into my AFMA menu on my 5D3. But when I then attach a Kenko 1.4x teleconverter between that lens and body, the body goes nuts. To regain control, I must remove the battery for at least 5 seconds. If I disable AFMA, I can attach and use the lens and teleconverter without a problem. So, is there any way to get AFMA to play nice with Kenko teleconverters, or must I always remember to disable AFMA before using it? And do Canon teleconverters face this same issue?

 

[Loswr]

1. No effect on MFD. Max mag increases by TC factor (1.4x or 2x).

2. You won't have that problem with a Canon TC. The body will treat lens + TC as a separate 'lens' - which it should, because a TC can (likely will) alter the needed AFMA. Some models/versions (versions as in 'blue dot' or 'green dot') of Kenko TCs have that issue - Kenko releases versions with new firmware (dot color) to work around such issues, no idea of there's a fix but I don't believe there is - one reason I've stuck with Canon TCs.

 

[miah]

1. No effect on MFD. Max mag increases by TC factor (1.4x or 2x).

2. You won't have that problem with a Canon TC. The body will treat lens + TC as a separate 'lens' - which it should, because a TC can (likely will) alter the needed AFMA. Some models/versions (versions as in 'blue dot' or 'green dot') of Kenko TCs have that issue - Kenko releases versions with new firmware (dot color) to work around such issues, no idea of there's a fix but I don't believe there is - one reason I've stuck with Canon TCs.

Thanks, Neuro. I bought the Kenko because it works with the 70-300L, whereas the Canon TC does not. The Kenko is a fine TC at a reasonable price and works well with all of my lenses with little perceptible degradation in IQ. This AFMA issue is the first problem I've encountered (mine is "Blue Dot," the latest version).

I expected, as you said, for the lens + TC combo to be treated as a separate lens with its own AFMA, but there's something amiss in the communication between the 3 parts. As soon as you turn the camera on with AFMA enabled and lens + TC attached, everything goes nuts. Even turning the camera body off has no affect--you have to pop the battery out to get the camera to properly reboot--and that's only after you've removed the offending lens + TC combo.

 

[Loswr]

IIRC, Mt. Spokane mentioned he had the same issue...and I believe he returned the Kenko TC.

 

[Mt Spokane Photography]

1. How do teleconverters affect a lens's Minimum Focus Distance?

2. When I AFMA a lens with FoCal, it gives me a figure (+3 or -2, etc.) that I manually dial into my AFMA menu on my 5D3. But when I then attach a Kenko 1.4x teleconverter between that lens and body, the body goes nuts. To regain control, I must remove the battery for at least 5 seconds. If I disable AFMA, I can attach and use the lens and teleconverter without a problem. So, is there any way to get AFMA to play nice with Kenko teleconverters, or must I always remember to disable AFMA before using it? And do Canon teleconverters face this same issue?

The Kenko will display the issue on 5D MK III and other newer camera bodies with certain lenses. It might be a problem for future lenses as well. Kenko has not issues firmware updates, so if they offer a fix, you might have to send it in for a upgrade or buy another every time Canon puts a new lens out.

I returned mine, because the only lens I wanted to use it on, the 100L wouldn't work with it, and my 100L requires AFMA.

My Canon TC's will not work with a 100L either, but there are no issues with supported lenses, and my MK II TC's cost the same as Kenko ones.

Kenko has yet to acknowledge the issue, or even the green dot / blue dot differences. They still say its compatible on their website.

 

[spturtle]

Maybe this has been discussed somewhere else already but:
1. Newer bodies have lens-specific and global AFMA, right? Does this crash also happen with the global adjustment?
2. What happens if you set up the AF adjustment while the teleconverter is attached?

 

[miah]

Mt Spokane, I appreciate your input. Again, I need the Kenko because it's the only TC that works with the 70-300L; Canon TC's are not an option. So, I have to decide if I need a teleconverter for my 70-300L more than I need properly AFMA'ed lenses. Tough call, especially because my 70-300L is so sharp, right out of the box.

spturtle, here was my sequence: I attached my EF 400 f/5.6 lens and ran FoCal to get an AFMA of +7. I then attached the Kenko TC and previously AFMA'ed 400, thinking I'd AFMA this combo next. That's when things went nuts. Once I realized my only escape was popping the battery, my only option was to DISABLE AFMA so I could use the TC + lens combo.

 

[Loswr]

The question is whether the combos with the Kenko TC are giving accurate focus. Because if they're not, and you can't apply AFMA, I don't think you can state that your Kenko TC actually 'works'.

 

[miah]

The question is whether the combos with the Kenko TC are giving accurate focus. Because if they're not, and you can't apply AFMA, I don't think you can state that your Kenko TC actually 'works'.

Yes--they work--the Kenko TC combos yield sharp images. I just want them to be as sharp as they can possibly be, hence my desire to test/adjust them in FoCal.

 

[spturtle]

here was my sequence: I attached my EF 400 f/5.6 lens and ran FoCal to get an AFMA of +7. I then attached the Kenko TC and previously AFMA'ed 400, thinking I'd AFMA this combo next. That's when things went nuts. Once I realized my only escape was popping the battery, my only option was to DISABLE AFMA so I could use the TC + lens combo.

Yes I got that, and I assumed you used "Adjust by lens", so I wondered if (after removing the current setting) you could set the measured amount in "All by the same amount" and then add the teleconverter. And alternatively if you could set up "Adjust by lens" while the Kenko teleconverter is attached. But the latter will most likely crash the camera at some point so I'm not asking you to try this. I have kenko teleconverters so if I ever get another camera it will have AFMA and I can test it myself (my 600D doesn't do AFMA).

 

[miah]

Yes I got that, and I assumed you used "Adjust by lens", so I wondered if (after removing the current setting) you could set the measured amount in "All by the same amount" and then add the teleconverter. And alternatively if you could set up "Adjust by lens" while the Kenko teleconverter is attached. But the latter will most likely crash the camera at some point so I'm not asking you to try this. I have kenko teleconverters so if I ever get another camera it will have AFMA and I can test it myself (my 600D doesn't do AFMA).

Hmm, interesting ideas. I might have time to experiment a bit with some of the combos you suggest, tomorrow. I did record all of my AFMA numbers for each lens, so there's no risk of losing them and having to retest. I'll let you know how it goes.