Kenko teleconvertor

[redmax]

Anyone got any experience of the following:

Kenko Pro 300 1.4X lens convertor.

I have been toying with attempting to get a little more reach with my long lens.

I use the 100-400L and after receiving a recomendation from a pro photographer I bought the Kenko

I am not at all dissapointed with the optical side. the picture still looks sharp but the autofocus is intermittent which is driving me mad.

I know that if I'm shooting something that is still then I can use manual focus but most of the time I want to track or pan moving objecxts like football etc.

The Kenko instructions say that anything down to F4 I should still get the autofocus but with the 1 stop loss for the convertor I can't seem to get less than 6.3 at 400mm (should be 5.6) or 5.6 at 100mm(should be 4)

I wonder if their values are AFTER stop loss not before?

Anyone help please?

I got it from Microglobe who will give a full refund but I want to keep it if I can get it working right.

I have cleaned all the gold contacts with ProGold cleaner and still intermittently works.

Anyone with experience of this issue please let me know

Thanks

[h4rri]

From what I've heard it's down to the loss of light into the lense at the long end. Are you getting trouble focusing at the full reach of the lense? Try with less zoom and see if this helps bud. Be interested to hear how you get on as I am considering buying on. I know I tried the 2x and that was awful at auto-focusing

[redmax]

Funny you should say that.
I originally purchased the 2x Kenko last Tuesday.
Got it home took it to a wildlife sanctury a few mins from my house and found that I had no autofocus at all.
The 2x convertor really works fantastic though taking my 400mm to very close to 800mm

Got some great close ups of swans, geese doves etc.

Anyway I read the paperwork whcih said that the 2x needs an aperture of 2.8 for autofocus but 1.4x only needs F4.

I exchanged yesterday and although I get some autofocus it is not consistent enough.
Once it is fitted I can't get wider than F6.3 at 100mm (140mm converted) even if pointing it at the sun!!
At 400mm (560mm converted) its more like F8.

Bummer really. I thought it may be electrical contacts.

If you read the Kenko paperwork I think they are really meant for prime lenses over 100mm not zooms.

I will try and find out a bit more from Kenko if I can.

[PaulBoy]

Comes out quite well in the tests here
HTH - Paul

[HCking]

Ah the old converter problems.

right a bit of info.

All non series 1 digital Canon cameras, will only use AF up to a total of f5.6 ie lens's + converters who's aperture is f5.6 or less. the 1 series digitals will AF upto f8.

Converters add either 1 or 2 stops to the lens's aperture rating ie

a 1.4x converter adds 1 stop to the lenses aperture rating
a 2.0x converter adds 2 stops to the lenses aperture rating

f2.8 + 1.4x conv = f4.0
f4.0 + 1.4x conv = f5.6
f5.6 + 1.4x conv = f8.0

f2.8 + 2.0x conv = f5.6
f4.0 + 2.0x conv = f8.0
f5.6 + 2.0x conv = f11.0

etc etc

so if you use say the 100-400 L with an aperture range of f4.5-f5.6

you will get

4.5 + 1.4x conv = f6.3
5.6 + 1.4x conv = f8.0

So unless you have a 1 series digital or some of the pro film slr you will not get AF.

the other way is to tape the pins on the converter so it does not send certain details to the camera this may enable AF in certain lighting conditions and is also dependent on how contrasty the area of your subject is you are focusing on.

see this link on fred miranda for details http://www.fredmiranda.com/TipsPage/

you can always manual focus and use the focus lock indication in the camera to tell you when you are focused.

[redmax]

Originally Posted by HCking

Ah the old converter problems.



the other way is to tape the pins on the converter so it does not send certain details to the camera this may enable AF in certain lighting conditions and is also dependent on how contrasty the area of your subject is you are focusing on.

see this link on fred miranda for details http://www.fredmiranda.com/TipsPage/

you can always manual focus and use the focus lock indication in the camera to tell you when you are focused.

Thanks for the link - I will try that tip, see if it works and report back.

If that doesn't work then can you please write a note to my better half saying how I really need to get a 1DS mk2

As I said the AF seems to work for a few seconds then just dissapears.

How would you manually focus on a footballer for example or a bird just about to take off?
I find the lens so long and heavy even on the monopod that MF is just to slow.
Its the moving objects I forsee being trouble like the great surfer pics from Newquay last month.

AF is a must for me.

[HCking]

Originally Posted by redmax

Thanks for the link - I will try that tip, see if it works and report back.

If that doesn't work then can you please write a note to my better half saying how I really need to get a 1DS mk2

As I said the AF seems to work for a few seconds then just dissapears.

How would you manually focus on a footballer for example or a bird just about to take off?
I find the lens so long and heavy even on the monopod that MF is just to slow.
Its the moving objects I forsee being trouble like the great surfer pics from Newquay last month.

AF is a must for me.

I think the AF with the pins taped will be too slow for that sort of photography, I used to try taping pins on my f4 lens with a 2 times on before i got a 1 series and it was painfully slow or just plain useless.

the 100 -400 L is not an f4 lens but starts at f4.5, so it shouldnt work at all unless you use the 1 series.

Keep us informed about the pin taping to see if that works.

I think the note to your wife would be better comming from your doctor, he could say you need a 1ds to stop the AF issue driving you mad !!.

STOP PRESS - Late addition

I have just been told by one of my mates (yes i do have some), that there is an old and new version of the Kenko pro 300 1.4x converter about.
And the old version will allow AF to work without taping the pins, but you get the same old problem, ie light levels contrast needed for the AF to function correctly etc. he also says he doubts if it would be any good for moving objects of any speed, as the AF tends to hunt a lot.

cheers

Mark