Contax Zeiss Lenses
This is going to outline the DIY process I undertook to modify these Zeiss photography lenses into an awesome cine set. Hopefully by doing this it creates a kind of “do this, avoid this” situation to stop things going wrong when you mod your own lenses.
If you’re looking for some in-depth information about the lenses themselves I highly recommend checking out the “Survival Guide” posted on the red forums.
https://www.reduser.net/forum/shooting-red/lens-tests/94346-contax-zeiss-survival-guide
I’ll start with some basics, there are two model variations across the range of Contax Zeiss glass, These are AEG and MMJ(or a few lenses are MMG). For the most part, AEG lenses will be cheaper to purchase because they have a Ninja-star shaped aperture ring* which causes jagged bokeh.
I took the plunge and all the lenses in my set are MMJ.
An example of “Ninja-Star” Aperture (AEG)
Standard Octagonal Aperture (MMJ)
First up, the lens mount. The lenses have a native CY mount which will adapt to anything with a flange distance less than 45.5mm. I have adapted mine to EF with a hard mount from Simmod lenses (I get all my modification parts from here). A quick note, don't buy those really cheap adapter rings because the CY versions of them just seem to fall apart and you will end up breaking something.
Cheap clip on filter
DIY Simmod hard mounts.
The Simmod EF Mounts fit over the existing mount so you do not need to take the camera apart completely to fit them, you just need to replace the screws holding that mount on.
I am a bit crazy however and have removed all the elements from my lenses upon purchase and cleaned them with Isopropyl alcohol to remove any dust and damage that may have accumulated over the years (Seeing as these lenses are from the 70s!).
The rear Lens element and group from my 85mm 1.8
The 50mm 1.4 in my set is the oldest lens in the bunch (just based off of serial number) and its focus markings had turned into a stained yellow.
I scraped the old stained paint off and replaced it using a white paint pen. (leaving the f16 green as that signifies an MM Lens)
If you wish to de-click the lens, you need to remove the mount and take out a small ball bearing which is held under the aperture ring, this will allow the aperture to open and close without a click and is a very common mod on these lenses. I also recommend buying some grease for these parts, I have used helicoid grease on mine but simmod also offer their own mixture.
The screws to get at these mounts are old, small and made of bad metal, be extremely careful when removing them and use a proper JIS screwdriver that comes with the simmod mounts. I had two screws burr on my 50mm and 25mm even when using the correct screwdriver, they are a pain. I advise heating the screw up first with a hairdryer/precision heat gun and applying a tiny amount of acetate into the screw thread to loosen it.
If you live in Melbourne and have burred one of these screws, congrats, it’s extremely hard to find a lens/vintage lens store that will remove them (If you know a local shop go for it) and you're left to drill them out on your own terms. I used some tiny drill bits from Hobby tools (https://www.hobbytools.com.au/drill-bit-high-speed-steel-0-5mm-3-pcs/) they break extremely easily so be careful. Use a vertical drill press and mark out the depth you want to go to before attempting this. You should be left with a hole down the middle of the screw which you can then sacrifice a cheap drill bit in order to jam it inside and finally screw them out.
Despite the drilling being easy and relatively painless, having a power tool near a $700 lens is not the best feeling.
That’s the mounts covered, thankfully the rest is really simple. Again from Simmod I have aperture focus wheel rings which are easy to install and have a metal construction and custom 77mm front filter thread converters. These allow 77mm filters to sit across the entire lens range as they have differing filter sizes and also have an outside diameter of 80mm so you're able to fit lens caps and Matte Boxes onto all the lenses without fuss.
The last and cheapest thing on this list are Tilta Follow focus bands. These are simple rubber rings that allow follow focus motors to do their job flawlessly. Because of the construction of the lenses, you're able to align these focus bands to the same height on all lenses, meaning that you don’t need to adjust the position of your focus motor when the camera is rigged up. I am going to eventually upgrade these to Simmod versions just so everything has a metal construction, these rings do the job well but can be annoying to work with a larger follow focus.
That’s it, good luck with your own mods. Below are and some stills from projects I’ve used these lenses on as well as the final look of the modded lenses at the moment.
