Teleconverters and Manual Focus

channeler · 04-12-2008, 08:15 AM

When putting the camera into manual focus mode with a Kenko MC7 x2 combined with the Sigma 70-300 DL Macro I find that the focusing mechanism still seems to be engaged ie when turning the focusing ring. When I attach the Sigma on its own the focusing ring seems to move more freely in manual mode. Has anyone else had experience of this?

Paul

**Peter Zack** · 04-12-2008, 08:55 AM

No Paul but try taking the 2 off the camera and see if you can turn the focus ring on the lens freely when the converter is attached. If it's still "tight" then the screw on the converter might be binding somehow. I'm assuming the 2x has the 'pass through' focus drive screw.

channeler · 04-12-2008, 09:30 AM

Tried them connected off the camera as you suggested Peter. The focusing mechanism is still "tight". It moves fairly freely but it's a bit like turning a clockwork mechanism. I also tried putting the TC on the camera first and then adding the lens, though whichever order I do it it doesn't seem to make any difference. I seem to remember reading somewhere that you should put the lens on the TC first and then put the combination on the camera, but I can't remember the reasoning. Anyhow, either way it doesn't make any difference to this issue.

Paul

**Peter Zack** · 04-12-2008, 11:07 AM

It would seem to me that the converter is binding the focus screw somehow. Last experiment. Take a small screwdriver and try to turn the drive screw on the TC off camera and off the lens (by itself) It should be very easy to turn with almost no resistance. I don't know if it's safe to lubricate the drive shaft. It may need some service or need to be returned if it doesn't free up. Any noise when you use the screwdriver?

If it's not easily turnable (is that a word?) then there is an issue with the TC. You may want to send a PM to PentaxForums.com - View Profile: jgredline
He seems to have tried almost every TC there is and may be able to offer more insight.

channeler · 04-12-2008, 11:42 AM

Will try to have a look at that Peter. In searching for sources of a Kenko Pro 300 3x (unsuccessfully as Kenko seem to have discontinued it for Pentax) I came across this post on the Amateur Photographer Forum where someone seems to have had a similar experience with a Tamron TC when used in combination with some Tamron zoom lenses:

Amateur Photographer & What Digital Camera: Problems with a Tamron 1.4X Converter

Paul

**Peter Zack** · 04-12-2008, 12:01 PM

There is a way around this Paul. You could put a very thin 'shim' over the drive screw on the TC (lens mount end) since the drive screw is spring loaded I think. That would disconnect the 1.4 from the lenses totally. Then the MF should work just fine.

I have one of these coming shortly and can get back to you on my testing.

*geoffox23* · 04-13-2008, 05:50 PM

I have similar problems to Paul.

Peter, thank you for this workaround. It is a little complicated to fit TC+shim to lens, but it allows easy MF of my Sigma lenses.

Unusually, I can use the Tamron TC1.4x with my Pentax and Tamron lenses and manually focus easily and smoothly without the need for a shim.

I will be interested in the results of your testing.

Geoff

Venturi · 04-13-2008, 10:26 PM

Originally Posted by channeler

When putting the camera into manual focus mode with a Kenko MC7 x2 combined with the Sigma 70-300 DL Macro I find that the focusing mechanism still seems to be engaged ie when turning the focusing ring. When I attach the Sigma on its own the focusing ring seems to move more freely in manual mode. Has anyone else had experience of this?

Paul

I've got the Kenko 1.5 and it does the same thing with all of my lenses (Pentax & Tamron). At first I thought it was binding somehow but when I pulled the lens/TC off the body and checked it out it's just spinning the passthru focus screw. Noisy as heck and a little stiff, but otherwise harmless as far as I can tell - the screw in the K10 body retracts out of harms way in MF.
I was hoping the MC7 2x was going to be a bit better built... guess not.

ukbluetooth · 04-14-2008, 06:13 AM

Originally Posted by Venturi

I've got the Kenko 1.5 and it does the same thing with all of my lenses (Pentax & Tamron). At first I thought it was binding somehow but when I pulled the lens/TC off the body and checked it out it's just spinning the passthru focus screw. Noisy as heck and a little stiff, but otherwise harmless as far as I can tell - the screw in the K10 body retracts out of harms way in MF.
I was hoping the MC7 2x was going to be a bit better built... guess not.

I confirm what you say. I dont like the stiffness and I am not sure that it is harmless.

On the TC there is a release button (between KENKO and DG). Just hold this in and MF works fine without any mechanical coupling.

channeler · 04-15-2008, 09:29 AM

Pardon my ignorance Peter, but how would you go about putting a "shim" on the TC mount?

The only release button on mine ukbluetooth is the release button for taking the TC off the camera. If that is the button you are referring to I would have thought it would be tricky holding that down while trying to focus but I'll give it a try.

Paul

**Peter Zack** · 04-15-2008, 10:52 AM

Sorry Paul I should have been more specific. Take a thin piece of plastic (or electrical tape) and cover the drive screw on the TC (lens side).. Then mount the lens to the TC. Turn the focus off on the camera body and you should be set to go.

Big Dave · 04-15-2008, 06:10 PM

Originally Posted by channeler

When putting the camera into manual focus mode with a Kenko MC7 x2 combined with the Sigma 70-300 DL Macro I find that the focusing mechanism still seems to be engaged ie when turning the focusing ring. When I attach the Sigma on its own the focusing ring seems to move more freely in manual mode. Has anyone else had experience of this?

Paul

Paul,
Did you check to see that the focus drive shaft retracts into the camera bayonet when placed in manual focus? It could be that the coupling shaft in the converter is binding. Did you get the same results with another lens? If not, it isn't the converter or the camera.

Dave