oldtimer
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Reged: 06/06/2005
Posts: 133
Loc: Outback Glos UK
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"Get a converter made by the same manufacturer as the lens" - so I have just got a Tamron 1.4X imported from USA
It works fine on my istD with my Pentax lens and my Tamron 90mm, but I cannot get manual focus with either the 18-200mm or 28-300mm Tamrons.
Auto focus works fine although there is a definite click the first activation as though something is engaging. Sometimes the focusing motor whirrs away with nothing happening. Re-connecting the adapter/lens combination usually sorts that problem out.
For manual focus the focus mechanism will not disengage to allow manual activation on either of the zoom lenses, whether fitted to the camera through the converter, or just to the converter itself.
It seems as though something is not connecting correctly but what?
I wonder if anyone else uses the Tamron and perhaps has a similar problem
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El Sid
Going potty
Reged: 14/04/2003
Posts: 10736
Loc: Sussex-by-the-Sea
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Quote:
"Get a converter made by the same manufacturer as the lens" - so I have just got a Tamron 1.4X imported from USA
It works fine on my istD with my Pentax lens and my Tamron 90mm, but I cannot get manual focus with either the 18-200mm or 28-300mm Tamrons.
Auto focus works fine although there is a definite click the first activation as though something is engaging. Sometimes the focusing motor whirrs away with nothing happening. Re-connecting the adapter/lens combination usually sorts that problem out.
Pentax lenses are driven from the body I believe? The click is probably the drive shaft engaging, my AF Nikons do the same. That said the the drive should engage every time, if it whirs without engaging this suggests something could be a bit out of line
Quote:
For manual focus the focus mechanism will not disengage to allow manual activation on either of the zoom lenses, whether fitted to the camera through the converter, or just to the converter itself.
I presume that both lenses can be switched to manual focus when fitted to the body alone? If this is the case and the lenses are switched to manual before adding the converter can they then be used in manual focus?
When you say the mechanism will not disengage do you mean that you can't move the switch to the manual position or the switch moves but the mechanism stays engaged? Both conditions might suggest that mechanism in the converter is a bit long and is somehow managing to override the declutching system in the lens. If this is the case check the drive pin on the converter, is it more proud if the mount than the one on the camera? It should also move fairly easily in and out as they are normally spring loaded and push in when the lens is mounted and pop out when the lens' drive coupling appears...
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Nigel
Completely BSRIPN 
ElSid Gallery
Terrorist?............or potential photographer?....... 
There are no people more opressed than those who willingly opress themselves
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oldtimer
member
Reged: 06/06/2005
Posts: 133
Loc: Outback Glos UK
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Quote:
I presume that both lenses can be switched to manual focus when fitted to the body alone? If this is the case and the lenses are switched to manual before adding the converter can they then be used in manual focus?
Yes, they all work fine.
Quote:
When you say the mechanism will not disengage do you mean that you can't move the switch to the manual position or the switch moves but the mechanism stays engaged?
The switch move ok, but the motor is still engaged so I cannot turn the focus ring.
Quote:
If this is the case check the drive pin on the converter, is it more proud if the mount than the one on the camera?
What should I be looking for? On the camera side is the pin which I thought operates the Aperture. On the lens side is a pin which may be the one to which you refer. It is spring loaded.
I have now tried all my lenses systematically and the results are below
There does not seem to be any way to format this data so the first yes/no on each line refers to Manual focus and the Second yes/no refers to Auto focus.
So they all work fine on Auto Focus, but the two Tamron zooms do not work on Manual Focus
Data for Tamron 1.4X Converter
18-55 Pentax SMC DA 3.5-5.6 Yes Yes
75-300 Pentax FAJ 4.5-5.8 Yes Yes
28-80 Pentax FAJ 3.5-5.6 Yes Yes
18-200 Tamron XR Di II 3.5-6.3 No Yes
28-300 Tamron Xr Di LD 3.5-6.3 No Yes
90 Tamron SP Di 2.8 Yes Yes
The Pentax 75-300 FAJ "works" in a mechanical sense but does not lock on in Auto - presumably because the aperture is smaller than F4
Only the Tamron Di II is Digital specific so that cannot be the problem, and it seems to have nothing to do with focul length. Nor is it to do with Pentax lenses. Paradoxically it is the Tamrons that are a problem
I suppose that providing it works in Auto, the problem is liveable with. However, it would be nicer if everything worked
I think it is time to email Tamron, but if you have any other suggestions fire away
One other thought. I believe that Sigma converters are temperamental when it come to non Sigma lenses, but has anyone used a Kenko converter and with what results?
Cheers
Graham
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El Sid
Going potty
Reged: 14/04/2003
Posts: 10736
Loc: Sussex-by-the-Sea
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Having looked at the manual it looks like the coupler is recessed (positioned at about the 5 o'clock position as you face the camera) and if the spring loaded pin on the lens side mates up with that when the lens is mounted then the pin is the coupler. It may be that it's a bit long on the converter compared to the lenses themselves though I'd expect as it's spring loaded this shouldn't really cause a problem. If the mode is switched to manual focus before the converter lens combo is attached to the camera does the drive re-engage as soon as the lens is locked into place?
I must say I can't see an obvious cause for the drive mechanism to refuse to disengage so I guess an e-mail to Tamron may be in order.
PS does it make any difference if you first mount the converter to the camera then add the lens rather than mount the lens to the converter first then put the whole lot on the camera?
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Nigel
Completely BSRIPN
ElSid Gallery
Terrorist?............or potential photographer?.......
There are no people more opressed than those who willingly opress themselves
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oldtimer
member
Reged: 06/06/2005
Posts: 133
Loc: Outback Glos UK
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After further experimentation, I am now convinced the problem lies with the converter/lens combination and not the camera.
With the lens off-camera the manual focus works fine as it should do since the drive is not connected to anything. There is a slight whirring of gears (presumably this is a very highly geared connection being worked in reverse as I turn the focus ring), but that is all.
On the converter, I have located the focus drive pin and this rotates freely. It does seem to stand marginally more proud than the one on the camera, but as you say it is spring loaded so this should not be a problem.
However when the two are mounted together, but still off-camera, the manual focus ring becomes very difficult to turn. It will turn but with a less than accetable crunching of gear wheels. It is certainly too stiff to allow precise manual adjustment and I do not think it does the gearing much good either 
Anyway, I have emailed Tamron to see what they have to say.
Cheers
Graham
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El Sid
Going potty
Reged: 14/04/2003
Posts: 10736
Loc: Sussex-by-the-Sea
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Sounds rather like the converter is the root of trouble though why it should struggle with Tamron lenses but not the Pentax is a mystery.
Fingers crossed that it can be sorted...
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Nigel
Completely BSRIPN
ElSid Gallery
Terrorist?............or potential photographer?.......
There are no people more opressed than those who willingly opress themselves
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channeler
newbie
Reged: 12/04/2008
Posts: 1
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Did you ever get a reply from Tamron? I have a similar issue when putting my Pentax K10D 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.
Tried them connected off the camera. 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
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