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[OM] Re: Tamron 1.4x problem...

Subject: [OM] Re: Tamron 1.4x problem...
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Sat, 09 Dec 2006 19:32:40 -0500
Ok, I think I've finally figured it out after digging out my Tamron 
24/2.5 with Adaptall II adapter and rereading your original post.

I believe the "hinged, spring-action gizmo which is not springing back 
into position" is the aperture stop down lever.  If I'm correct the lens 
mating side of that should look like a small ramp.  It's a cam that 
rotates into position and pushes up on the diaphram roller wheel on the 
back side of the lens.  At least on an Adaptall II mount.

When an Adaptall II mount is attached or removed the lens has to be at 
full aperture AND that cam on the mount must be rotated fully clockwise 
in its travel.  Normally it is under spring pressure and is normally in 
that position.  But if the spring is broken or detached it may not be in 
the proper position when the lens and converter or adapter mate.  This 
will prevent the lens from latching into position and rotating the 
aperture ring might loosen the lens.  But I don't believe it really has 
anything to do with the aperture ring, it has to do with rotating the 
unlatched lens which you are doing inadvertently by rotating the 
aperture ring.

The spring that controls the stop down cam should be visible in the gap 
directly opposite the cam.  Compare with your 2X or an Adaptall II mount 
removed from the lens.  If you manually move the cam to the full 
clockwise position before attaching the 1.4X to the lens you will 
probably get the lens to latch and lens and teleconverter will not 
separate when rotating the aperture ring.  When properly latched the 
lens can't turn.

However, even if you manually move the stop down cam into position 
before mating lens and converter I don't think the lens will work 
properly.  With no spring pressure on the cam it may not return to the 
full clockwise and full diaphragm open position.  Ie; the camera may 
force the diaphragm closed but without the spring pressure on the return 
the diaphragm may not reopen or may do so sluggisly.

Also note that there is a second spring in another race directly below 
the stop down cam which is the return spring for the DOF preview lever. 
  If these springs are broken or detached it looks like it would be 
necessary to at least partially disassmble the converter.  I don't have 
a converter here but the mechanism has to be very similar to that in an 
Adaptall II mount.  And that looks like it could be pure hell if you're 
not careful.  An Adaptall II mount appears to have about 10,000 tiny 
ball bearings inside.  Whatever you do don't let them loose.

Good luck,
Chuck Norcutt



Chuck Norcutt wrote:

> Ignore my uneducated ramblings.  I just now finally remembered that the 
> Tamron 1.4X teleconverter doesn't have a normal lens mount flange like 
> other teleconverters.  It attaches directly to the lens ala the Adaptall 
> II mount and the liberated Adaptall II mount then gets moved to the back 
> of the teleconverter.
> 
> Never mind.  I haven't a clue.
> 
> Chuck Norcutt
> 
> Chuck Norcutt wrote:
> 
>> Then it's difficult for me to see how this is not the fault of the 
>> lens or, in the case of the Tamron, the Adaptall II adapter's latch.  
>> The 1.4X is perfectly passive in the connection.  It only provides a 
>> notch in its front flange to accept the spring loaded latch on the 
>> lens.  No different from the camera body's mounting flange.  Hard to 
>> imagine there's something wrong with the 1.4X's front flange that 
>> would prevent the lens from latching.
>>
>> With the lens removed, what happens with the lens release latch when 
>> you press the release button?  It should be spring loaded and you 
>> should be able to see the latch moving in and out near the bayonet 
>> flange in line with the release button.
>>
>> Does this happen with other lenses?
>>
>> Chuck Norcutt
>>
>> Donald wrote:
>>
>>> Chuck Norcutt wrote:
>>>
>>>> Sorry, but after Alan's note I realized it's still not clear to me 
>>>> what's separating.  Is the lens separating from the adapter at their 
>>>> normal mounting flange juncture (lens mount not latched) or is the 
>>>> lens separating from its Adapatall II adapter and leaving the 
>>>> Adaptall II on the front of the 1.4X (adapter latch not latched)?
>>>>
>>>> Chuck Norcutt
>>>>
>>>>
>>>
>>>
>>>
>>> The former. The problem is definitely with the front of the 1.4x. 
>>> Whatever is behind the 1.4x remains attached to the 1.4x, everything 
>>> in front of the 1.4x becomes detached.
>>>
>>> I think that covers most of the bases..! ;-)
>>>
>>> D.
>>>
>>>
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> 


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