EXT to LDS cable

Thu Jan 11, 2018 9:21 pm

I'm looking to move to a WCU-4 with my Mini. Unfortunately I'm not running PL mount glass so Im curious if the EXT to LDS cable will allow me to run the Cforce Mini motors and utilize the radio in the camera. Is the LDS cable basically an Lbus port?

Thank you in advance
Jonathan Houser-
Posts: 3
Joined: Wed Feb 08, 2017 8:57 pm

Re: EXT to LDS cable

Fri Jan 12, 2018 5:56 am

Hi Jonathan,

I am assuming you are talking about this cable: K2.0012628 LBUS to AMIRA/Mini EXT. Unfortunately the setup you proposed currently does not work. Cforce motors connected to the Mini using the LBUS to EXT cable will not be recognised by the camera. This cable is intended to connect the master grips to the Amira and the Mini using the EXT connector.

If you are using EF lenses with built in motors you can control many of those using the WCU-4 connected wirelessly to the mini without the need for external motors.
If you are using EF lenses that require external motors, I'm afraid you would need to add an AMC-1 (K2.0005872) connected to the Mini using: Cable SMC/EMC/AMC-1 to ALEXA Mini EXT (K2.0007730).
Silvan Liu
Service ARRI East Asia Pacific
Silvan Liu
Posts: 35
Joined: Mon Nov 23, 2015 7:11 pm
Location: Hong Kong

Re: EXT to LDS cable

Sun Jan 21, 2018 11:21 pm


About EF lens control. The focus control abilities of the WCU-4 using the motors built into AF lenses are very limited. Arri's EF lens control implementation is mainly targeted at working with the master grips that do not have hard stops (and this seems to work really well). With the WCU-4 it's a different story because of the hard stops. With some wrangling it can be used to "set" focus, but it is more or less useless for regular focus pulling.

There is a 3:rd party solution from Optitek -- their EF mount + Optitron2. This works really well and the focus control has exact repeatability, hard stops and you can mark custom rings for regular focus pulling. But, you're obviously loosing all of the other functionality you get from the WCU-4.

Also, you must understand that if you go the AMC-1 route, you get basic lens/motor control and start/stop, but none of the other functionality of the WCU-4 like camera control playback etc... Also, lens file transfer and UDM integration is not possible.

If you use an UMC-4 instead of the AMC-1, you can integrate UDM and work with lens files, but you can NOT use c-force motors.

In both cases (AMC-1 and UMC-4) It will only work with lenses with proper hard stops -- adding gears to AF-photo lenses without hard stops will nor work since there is no way of manually calibrating (that I know of -- perhaps there is a work around?)

I wish Arri would develop an additional EF-lens control implementation for AF-lenses like the Optitek one, for use with WCU-4. This would be very useful!!!

Another thing also to keep in mind is that lens control using built in AF-motors can be quite noisy (varies from lens to lens in both volume and character) -- to the point that it may not be usable for sync sound drama/doc.

Kind regards,

Joachim Heden
Posts: 10
Joined: Wed May 31, 2017 5:15 pm

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