Tamron 1.4X

I have just got a Tamron 1.4X converter, imported from the States, to match my Tamron lenses.

It works fine with my Pentax lens and my Tamron 90mm, but I cannot get manual focus with either the 18-200mm or 28-300mm.

Auto focus works fine although there is a definite click the first activation as though something is engaging. The focus mechanism will not disengage to allow manual focus on either lens, whether fitted to the camera through the converter, or just to the converter itself.

I wonder if anyone else uses the Tamron and perhaps has a similar problem

Graham

Unfortunately all my Tamron gear is old adaptall 2 manual focus, so I can't really help but I do have Pentax AF lenses and the Pentax 1.7x AF converter.
This is really designed for MF lenses and there is no drive connection for AF - so an AF lens works in MF only (the adapter does the focusing).
I would have thought that the Tamron adapter would work in the same way and selecting MF on the camera will disengage the drive to the converter.

I'm quite intrigued by your description of the problem - are you sure that the lenses auto-focus when attached to the adapter?

Just found the following, there is an AF coupler between converter and lens. I think selecting MF on the camera is all you can do but the lens and converter will remain coupled.
http://www.tamron.com/lenses/prod/teles.asp

These adapters aren't really designed for wide-angle lenses or zooms that extend wider than 70mm, so it might be that the inner barrel of the lens would protrude too far into the adapter - just a thought!

Cheers Kimbo.

Yes, but I must check ther FLs of the lenses to see if that is relevant

This just gives me the prices and brief specs of the converters. Should there be some sort of explanation?

I will try and get back tomorrow after I have tried a few experiments.

The link shows a picture of the 1.4x converter and I can see the AF coupler.

The 2x converter shown appears to be in Canon mount and has electronic connectors for the USM lenses.

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 (unless I get a split image focus screen! ). 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

EDIT some time later

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 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

Got an email from Tamron the other day:

quote:-
"I'm not saying it is a problem. Try to look at it this way - if your have a
gear train of lets say 6 gears and there is a certain amount of force
needed to rotate it, then you add another 4 gears, it will be harder to
rotate the gear train. Thats what happens in this case. However, I would
like to see it to see if it is a normal amount of torque or if there
actually is a problem."

I cannot see why there should be 4 gears (or indeed any gears) in the converter. In fact as far as I can see it is just a straight through linkage. I suspect the alignment is not spot on so when trying to turn the gears in the reverse direction it binds.

So there you have it, perhaps you should not use a Tamron converter with a Tamron lens if you want to use manual focus.

And No, I am not sending it all back to Tamron. I will use the Pentax lens instead.

The next converter will be a Kenko (Kenro), the next lens a Sigma

That seems like a very strange response to me, almost like they're just trying to fob you off!

Did they actually confirm whether or not the lenses were all suitable for that particular converter and if there were any limitations?

There is obviously some gearing involved but I think he was just trying to make a point, ie. that you would increase the resistance (felt when turning the ring manually) when you add the converter but I see no reason why it would become so stiff as to be impossible to use effectively.

With the lenses that do work, have you noticed any significant difference in how stiff they are? - if not, then I would suggest that seeing as most of them are also zoom lenses, that his quite reasonable gearing analogy doesn't really stand up.

As for the 'definate click' that you hear when first engaging the drive, I would imagine that it would be more noticeable with some lenses than others because of the different ways they are built and zooms do tend to have a looser construction than primes (more moving parts that sometimes move in opposite directions).

It is certainly an intriguing question because presumably all your lenses focus easily in manual mode on their own and I don't see why adding the converter would make such a difference to just two of them

I rather got that impression.

Nope. What you have is virtually the full text of the email. An earlier response simply said:
There is a problem in that the two Tamron zoom lenses cannot be put into manual mode (ie disconnected from the gear train) themselves, unlike the 90mm which does disconnect.

I agree that is is more difficult to rotate a highly geared train in reverse, but the attachment of a non geared converter should make no difference unless the linkage does not exactly match up.

The other lenses are a little stiffer but prefectly useable. The gearing argument is irrelevant because there are no gears in the converter. However, the Pentax lenses are much smoother suggesting more precisely engineered gearing. I suspect that the Tamron gearing is pretty coarse by comparison which would lead to much stiffer reverse turning. Maybe that is how they keep the price down.

Anyway, if anyone else out there is thinking of mating a Tamron lens and Tamron converter, then be warned that it might not go as smoothly as expected. They are good value for money, but obviously not without their problems.