conurus N-mount to EF-mount conversion with autofocus and automatic aperture diaphragm: installation questions (FAQ)

WARNING: you will void your lens warranty by modifying your lens.

Initial customer feedback suggests that it is difficult to find a camera shop who is willing to perform this installation. We believe that your successful deployment should be painless and trouble-free. Therefore, we are now offering installation service. Please review our FAQ for pricing.

N-mount lens + $$$ = EF-mount lens

Do you have any installation pictures?

Yes, please refer to our Installation Guide.

Why do I have to measure the thickness of the original mount ?

We measured the mount thickness of a lot of N-mount lenses and it varies significantly from lens to lens. We have no way to predict the thickness of your OEM mount. Every N-mount lens has a variable number of copper spacers to make sure the backfocus (the distance between the rear element and the film plane) is correct. Our mount is made thicker than the OEM part so that you will match their thickness by removing some of the copper spacers. We tried a good number of N-mount lenses and most of the time we are able to get the thickness matched very closely by removing the right combination of copper spacers. If the difference is excessive, you can make a copper spacer out of copper foil using an existing one as template.

Why do I have to make measurements with a micrometer, but not with a caliper ?

Some of the OEM copper spacers we find in a N-mount lens are very thin. Calipers, even so called "digital" ones, are not accurate enough for making such small measurements. Just because the tool claims 0.01mm accuracy does not necessarily mean it is actually capable of doing so. If the measurement is not accurate, you do not get good performance from your lens and you may run into AF accuracy problems.

Why do I have to use a JIS Type-S screw driver for the disassembly ?

An ordinary #00 or #0 philips screwdriver apparently works, but it is not the same thing. If you strip the screw, you will never be able to remove it. It makes more sense to use the right tool than to put the lens at risk. We have had a customer report that even with a JIS screwdriver one of the screws still stripped. You need to apply a lot of downward pressure while turning.

Is the modification reversible ?

Soldering is required and the modification is not reversible. You also need to file down the tab protruding from the shroud of the 2,8/17-35 zoom by 2mm, which of course is an irreverseible modification, or that protruding tab will hit the mirror and cause damage.

Why do I need temperature-controlled soldering equipment ?

If there is no temperature control, excessive heat may be applied to the flex circuit of the lens. If you melt the flex circuit, it can only be repaired by complete disassembly of the lens and replacement of the whole flex circuit by the OEM at great cost. (Sorry, at your expense.) Additionally, the soldering equipment must be ESD-protected to prevent damages to the lens' electronics. Use proper precautions when working with devices which are sensitive to electrostatic discharge (ESD).

What temperature should I use ?

650 degrees F or 343 degrees C worked for us. You should not use a higher temperature than 700 degrees F, and even at lower temperatures the flex circuit may melt if you do not do it quickly enough.

Why do I have to store the circuit and the lens in a dry box before installation ?

Moisture trapped in integrated circuits will rapidly vaporize and cause damage when soldered. Before installation, it must be stored in a dry environment. It is recommended to do the same for the lens as well. After installation, the circuit will not malfunction even in a damp, humid environment because there is no heat to cause damage, but it is not a good idea for the lens anyway.

What happened to the solderless replacement mount ?

The solderless replacement mount for Vario-Sonnar 24-85/3.5-4.5 and Makro-Sonnar 100/2.8 has been discontinued. It was not reliable and in some cases did not work at all. After this initial setback, we have determined that the only way to make a reliable connection is by soldering. We understand the soldering requirement further limits our already small customer base, but we have no choice. Existing customers of the solderless mount are encouraged to migrate to the soldered version.

Can I install the modification kit on a Contax N lens by myself ?

No, unless your profession is electronic camera repair. This is not a DIY installation. There is no reason to put an expensive lens at risk. Pay a professional to do it. I am explaining all the complexity of the installation to you in great detail so that you do not attempt DIY, although all these are second-nature to a competent repair professional. We have had a customer report of a failed DIY attempt. Please don't try!

I do not have or know how to use the proper tools but I still perform a DIY install anyway

For 50/1.4, keep all shims. For all other lenses, remove the thickest shim you find in the lens. For 17-35, really, accurate measurement is crucial to successful deployment. Wide angles are much more sensitive to errors in registration distance than telephotos.

Can I install it on the NAM-1 adapter ?

Please don't! Please wait for our C645 product as it will have different circuitry and different firmware.

What is your manufacturing tolerance ?

We are unable to give an answer because tolerancing is a very complex topic. In our design different dimensions have different tolerances based on need. If you hear a simple answer to this question from some other manufacturer, I would question if they are giving an oversimplified answer just to satisfy their customers' curiousity, or worse, don't understand what tolerancing is about at all.