Tamron Converto 135mm

[Stephen]

A query....I have bought a cheap 1959/60 Tamron 135mm Converto lens, Ebay strikes again!, with the case, and the 2x teleconverter that Tamron originally supplied it with.

Now these Telephoto lens were the first lenses that Tamron ever marketed, and it was supplied with two mounts in the kit, a Pentax M42 screw mount, and an Exakta type adaptor.

These adaptors were the very first " T mount " lens adaptors.

The original instruction sheet showing the two "T Mounts"

But these adaptors are missing from the case, I knew this before purchase, and had thoughts of making the adaptor myself, but it turns out the "T Mount" is same body as the modern T mount, but the internal ring has a smaller hole and a 37mm x .75mm pitch, rather than the later 42mm x .75mm pitch that all later T mount lenses now have.

Before a session on the lathe to make the 37mmx.75 mm internal ring to change it into a modern T mount, .....does any body happen to have a genuine 37mmx.75 adaptor....just asking in case!!!!!

These lens are rather fun, a very compact 135mm, and even with the Teleconvertor on, (stopped down), produce good results, and double up the focal length on micro 4/3 of course, it even shares the 38mm filter with the Olympus 14/42 Zoom.

Stephen

[Stephen]

The Tamron Converto 135mm lens has arrived, at last, and looks in fine condition, bar some dirt on the outside of the lens in the 135mm section.
A case but no hood, no problem, but no T2 adaptors, the compartment in the case is empty. Not a massive problem as modern T mounts are the same thickness, but this lens has 37mm thread, the earlt T mount, not the 42mm size now used.
So a session on the lathe to turn and thread a 37mm x.75mm threaded inner collar for a modern mount. I have a spare old Pentax fit which can be altered, and then it can fit a micro 4/3 to Pentax to work with Digital, or go straight on to an M42 Pentax fit reflex.

Stephen.

[truls]

Interesting, are the quality of those early Tamrons comparable to for example Nikkor or Canon at the time?

[Stephen]

The Tamron Converto 135mm lens, now cleaned up a bit, and fitted with a suitable T2 mount, which is a real special, as it is threaded 37mm x.75 not the modern 42mm x.75. This was made by me tonight, a much quicker job than I expected, as the 37mm thread is the same pitch as filters and an old stepping ring could be used, saving cutting the 37mm thread from scratch. The modern T mount had the 42mm machined out by boring, and the turned down 37mm was loctited into the recess, with securing wires.
Result is a nice vintage early type T mount.




The 135mm section is small, very small, only 3 inches, and the 1.77x convertor does not increase the size much. It looks a bit odd on the T mount, and a Micro4/3 converter, but is still a very small size for an effective focal length of 450mm








4/3 plus T2 mount.


135mm lens and mount.


Complete lens and mount

The Tamron lens came with the case, but no adaptors or hood, a hood will have to be made, 38mm filter size is quite uncommon, but a Skylight 1A, Dawn Brand, Japan came with it. There is a nice quality original metal screw in black finish lens cap.

The lens needs proper testing for focus to infinity tomorrow, the T mount ring can be adjusted, but it does not seem that far out, I suspect the early Tamron mount was the same thickness as later T2 mounts.

The performance of the Converto lens is said to be good, especially the 135mm on it's own. It is not in Nikon league in theory, but Tamron were out to make a reputation with these lens and put a lot off quality in for the relatively low price. They had only sold the Telescope type lens before this, their very first proper lens.

If it works OK it suits Micro 4/3, due to the small size, and I can't think of any 450mm lens that are this small!! I doubt if the converter will be used much, it does waste light, but with the high ISO settings on digital, it may be useful. I can see the 135mm (270 on 4/3), being used quite a bit.

Stephen.

[lloydy]

That's a tiny lens, and a very good looking one. Be sure to post some pictures from it, Id love to see how it performs.
That's a very nice job with the adapter as well.

[Stephen]

I had feared all along that the T mount on these early lens was not only 37mm not 42mm, but it was also a bit thinner, and it has turned out this way, the Tamron Converto 135mm does not focus more than 15 feet away at present.

The drawing on the instruction sheet is near scale and appears to show the mount at about half the thickness of the modern T mount, so back to the lathe, and try to reduce the thickness as much as possible, without ruining the set screws grip on the inner ring.
I can test it on a split screen Edixa that is accurate, just have to trim it till accurate at infinity, by trial and error. There's no way of working out how much to remove, as the original T mount relation ship to Pentax is unknown and could only be worked out from another lens, or measuring an original adaptor.

Stephen

[Stephen]

I also suspect that Tamron increased the overall diameter as well, when they changed the T mount, as the mount looks a bigger diameter than in photos on the net. Reducing it is not possible as there is an undercut inside, which takes the set screws, and I would lose the knurled black finish.

Stephen.

[Stephen]

Taken whilst testing for infinity, a hand held shot at six feet of Lichen on a tree, lens at F6.3, seems OK so far. More as soon as infinity is found!



Stephen

[Stephen]

The T mount adaptor has proved a bit of a problem, the old type T mount turns out to be about 3/16th thick, not the 3/8 of the newer type! I have machined down the interior part to the correct thickness, less a thin .5mm brass washer, which can be thinned down, or added too, with thin paper.

The infinity mark is reached and passed a fraction on both an Edixa and a Fuji 42mm SLr, and it agrees basically on the Olympus, but appears to go fractionally more beyond infinity, than on the reflex's. It is better to go beyond a fraction than not reach it.

The old retaining screws in the T mount are now on the edge due to the reduction, awkward to remove any more metal for appearances sake, part from reducing it and fitting a sleeve to cover the old holes up.

As the weather is bright today, I'll give it a good test this afternoon as a 135mm , then as the 225mm with the adaptor, which I know already is poor at max aperture, it has to be stopped down to get sharp with it added.

Stephen.

[Stephen]

Well, the Tamron lens works....


Focuses to Infinity, and to the lens scale...Focus on figure....


Focus on the Dog and Lady.....


Close up on flowers.....



Usual test view that I use, over the River Medway.....


Over the Playing field view

The tiny Tamron 135mm lens works quite well, but not quite Leica league!.. but very usable, and quite sharp at F8.0......

But there is a strange issue on some of the other test shots, using an Olympus PM-1, I used a monopod, and the images where I used the monopod, have a micro double image on tiny highlights, where I think the Olympus IS system is fighting the Monopod. It makes very fine vertical lies look "wavy", only to a tiny degree, but it is there.

I will try another set tomorrow, with the Image Stabilisation switched off, with the monopod, or tripod, and some hand held at higher ISO settings, with the IS manually set to 135mm to match the Tamron-Converto lens more exactly.

Stephen.

[Stephen]

100% crop clearly shows the IS issue, causing on this shot, wavy vertical lines, on others a double image at micro level.


It's the Image stabilisation causing the strange "micro double image on highlights" issue with the Monopod, and not reading the instructions carefully, where it clearly states turn off IS when using a tripod, in my defence it did not mention Monopods. (Good excuse?)....

Being a manual 135mm I should also have set the Olympus IS to suit 135mm as well, as long as I am hand holding, which will need a higher ISO as well.

The bad setting and the monopod cause tiny vertical white lines to "shimmy", distorting things like windows in the background. It is slight at normal size, but full or magnified it shows.

It vanishes with the IS set properly, or off with the Monopod, you have to be very careful with settings on these Digital cameras. The very same issue was spotted on the HD Video setting, where most people turn the Is off due to "jitters" when filmimg with a tripod. It is rumoured that Olympus have noted the problem, and may address it in an up date of the software. It is not confined to the PM-1, but only the latest models, the PL-1 I also have has no problems with video, but it still states using a tripod, then turn the IS off...

Stephen

[Stephen]

Better, with IS off and tripod, but there is still a bit of "micro wooble", but it is at the limit of Jpegs accuracy, so not all the lens! I will try both cameras on raw to check, and try a friends OM-D to see if it just the limit of the sensor. I had not noticed the effect with other lenses, and I suspect the Tamron is sharp, but requires an increase in contrast to rival modern lenses, which produce a better image without apparent "wobble".

I think this might be affecting the Mirror lens as well, contrast increases in photoshop or other programs make the limits of a Jpeg show more.

So older or low contrast lenses must not have the contrast increased too much with digital images... we live and learn!

Still....a reasonable standard for a 50 year old lens.

Stephen.

[Stephen]

I'll also test the Tamron lens on film, this should be all right as these sort of issues are not there on the negatives and the neg is 4x the area of the sensors.

Stephen.

[Stephen]

Ouch,...... I have been rather greatly under estimating the Tamron lens, in comparison with the Olympus Standard Zoom, magnified at 42mm to give about the same shot, the Tamron is simply streets ahead on sharpness.

I have just tried both on an OM-D and the Tamron is sharper than the 45mm F1.8 by a good margin, difficult to exactly compare due to the difference in focal length.

So the slight "wobbles" etc are down to it being very sharp, albeit at a lower contrast.



With Standard 14mm to 42mm zoom on same view, much, much softer!!! even after a tweak with Photoshop.

So with a hood fitted to help contrast, this lttle Tamron lens looks like a really sound few quids worth, and I have not tried the converter section as yet![/i

It has also made me think about the Sigma prime lenses, 19mm and 30mm, a friend in Canada is getting fantastic results with them, very sharp indeed, sharper than the zoom lenses by far.

Stephen.

[Stephen]

Olympus 14mm to 42mm zoom......cropped


Tamron 135mm at F8....disregard the arrows!

Makes you want to give up using Zoom lenses!.......Have lens makers really advanced much, remember this Tamron lens is 50 years old, no multicoating and just four elements, (I believe). It a cruel comparison with the shorter zoom lens, but look at the difference!

Stephen.