I was hesitating to convert a Zoom lens, but several clients asked for it. This is
the best option for an affordable and available second hand Leica walk around zoom lens. It is a true Leica design made by Kiozera in Japan, much better than other alternatives, look at this review:

The current version of the 35-70 is slower at f/4, but is a complete redesign. It is housed in the same
 barrel as the ROM version of the 28-70, and both lenses are manufactured in Japan, however the
35-70 is a new design created in Solms by the Leica "home team" and it shows. The performance
of this lens is absolutely stunning, at all apertures and focal lengths. Distortion is almost unnoticeable,
the sharpness and contrast rival the fixed focal length Summicrons (35 and 50), and it has a very
useful macro setting.
After first look inside, we realized the construction is very different  than the older
3 cam lenses, the only way to install a Leitax bayonet is performing a minor surgery, the good news is that this operation will not  harm the functionality of the lens, it will remain being a full operating Leica lens if used again on a Leica camera.

So let's begin with the instructions, this is the Leica Vario-Elmar 4/35-70 with ROM contacts.

First, unscrew the black dust shroud.
Unscrew black ones

And remove it.
unscrew ROM

Now unscrew the ROM contacts strip.

Use the plastic tool to liberate it, take care here, we only want to lift it a millimeter

Now, unscrew the Leica bayonet.

And remove it, look at the picture, move the bayonet to this side to liberate it from the ROM strip.

Find the small ball, usually remains sticked to the bayonet, save it, and put some grease on the spring hole to keep the spring there.
flat cable

This is the flat signal cable for the ROM contacts.

As you can see, I've removed the aperture ring. Just raising it.

And this is our first problem, the original bayonet reduces here to allow the cable to pass.

But our Leitax bayonet doesn't, so we have to file  a little bit the lens base. First protect the lens against metallic particles that will produce the filling, note I put a piece of raw cotton under the kitchen paper that will catch the particles. Also clean the grease where the paper mask tape have to glue.

And start filing, remember there is no hurry. We have to make room for the flat cable here.
one side

One side almost ready, we need only to file for the thickness of the cable

A little bit more filing
45 deegres

Then make an additional filing at 45 degrees to remove the sharp edge.

With a piece of raw cotton, remove all the metal particles before removing the protection
needs more cleaning

Some particles remaining, I used the plastic tool point wrapped with raw cotton to catch the difficult ones
second problem

And now look at our second problem, this small lever just next to the R cam.

Prepare the operation theater , don't forget the raw cotton under the kitchen paper, to seal and trap .

And this is the result, make sure the aperture ring is at f4, to immobilize
the lever, also I think would be better to work with the lens on its side, to make the gravity help us.
replace the small ball

Replace the small ball on the spring and leave some grease on it.
screw the Leitax bayonet

Now screw the Leitax bayonet for the final check.
check here

Almost ready, but first check if the diaphragm blades return freely or get catched wide open. In this case the problem is this square piece where the spring loaded lever is attached, we have to use a piece of sand paper on the Leitax bayonet at the contact zone.

After some trials the blades are free and we can install definitively the Leitax bayonet.

And finally we have this great lens on our Pentax camera.

You can get the Leitax bayonet and the necessary tools at our homepage
Back to Leitax