Arri WCU-4 & UMC-4: lens Mapping

WCU-4 LENS MAPPING 

Arri WCU-4 & UMC-4 Lens mapping

Lens Mapping with Arri WCU-4 & UMC-4. I don't know what your opinion is on this, but for me it has always been very important to be able to change a lens quickly when I'm using wireless focus control systems in moving situations such as steadicam, crane or handheld shots. In these situations a conventional focus control could transmit unwanted movements to the lens and therefore to the shot.

Previously, what was usually done was to prepare pre-marked rings in the check and change them while the lens was being calibrated, although I had always dreamed of being able to find a more practical method that would always work the first time. A few months ago an Arri product distributor held a lens mapping workshop with the Arri WCU-4 that unfortunately I was unable to attend because I was not in Madrid at the time.

WCU-4 LENS MAPPING

So I thought I'd try it without anyone explaining it to me first, to see if it's as easy as they say. As always, I have to thank the guys at Camaleón Rental for putting at my complete disposal an Alexa XT, an Amira, a set of Zeiss Standard Primes and a Cooke s4i, as well as a Fujinon Cine Cabrio zoom and obviously a complete WCU4 system with 2 CLM4 motors and a UMC4. The choice of lenses and cameras to test it with is due to the fact that I was curious to test the system on different cameras (one that incorporated the "brain" of the wireless focus system and another that didn't) and with different sets of fixed lenses (one that didn't have LDS and the other that did). Finally, I also wanted to try it with a zoom that had LDS.

So I got to work, starting with the Zeiss Standard Primes T2.1 mounted on the Alexa XT, without needing to use the UMC4, since the motors are adjusted directly to the camera body. The mapping system is extremely simple and the WCU menu is exactly like the camera menu. It is designed in an intuitive and very accessible way. Select the option Menu>lens data>create lens file (or edit if you already have part of the mapping done). From here we can select the brand, series, focal length and serial number of the lens. You can be very specific by putting all the data or not, that is up to each one. Once the lens identification is finished, the program directly asks us to set the focus ring to infinity and mark it. Then the focus puller or camera assistant will go to the minimum focal length and from there we will put all the intermediate marks. Don't forget that to modify the preset marks you can use the zoom control and the red user button located just behind it to adjust it.

A very important recommendation: if you make a mistake, DO NOT press the BACK button, as this action will make you exit the menu losing the marks you had already inserted. What you have to do when you make a mistake is press the DOWN button and you will return to the previous mark, with the possibility of modifying both the mark and the reference number. Once we have finished with the marks we can press the "finish" button and we will start mapping another motor with the iris, or we simply save the file by pressing the button that says SAVE FILE.

The file we just created is now saved on the SD card located in the WCU slot. The truth is that at first I thought that the LDA files would be saved on the remote and that it was possible to activate them from there, but unfortunately it is not that simple. If we shoot with an Alexa Plus or Mini, it will be necessary to transfer the LDA file to the internal memory of the camera where we will be given the possibility of saving and naming it. This operation is much easier and faster on the Alexa XT plus, as the camera offers an SD slot, so all we have to do is take the SD card out of the handset and put it in the slot on the camera body and from there save the desired files on the camera. In the case of the Alexa Mini the operation is slightly more complicated, since as it does not have an SD slot it will be necessary to transfer the LDA files through a USB pendrive with the camera settings and from there we can load them into the camera. Once this is done, every time we put a lens we will have to tell the camera which lens we are using via the menu. In very rushed shoots this could be interpreted as a nuisance, but given the extreme utility of having the marks already made on the WCU4 display, I think it is worth optimizing it a day before the shoot.

This will work for cameras where we have the option to load LDA files, although this will not always be possible (we would like to always shoot with Alexa XT!). In the case of cameras that do not allow this option, such as the Amira, we will need a device to be able to connect and power the motors and receive the signal from the handset. With the UMC4 we will perform all these functions, but we will also use it to store the LDA and send them from there to the WCU. On the main menu page there is a section called Lens. Once we are there we can add the LDA that we want to transfer from the SD card of the handset to the slot of the UMC4.

Once the LDA has been copied (we can include the lenses that we use most often in a favorites list) we will be ready to shoot. My advice is to attach the UMC4 to the camera body in a position where we have easy access to the display and buttons, since every time we change lenses we will have to select the one we are using to send the signal to the handset. The most significant difference I have noticed between mapping lenses without and with LDS is that the latter give the possibility, in cameras that support it, to see the iris, focus (and zoom in the case of a non-fixed focal length lens) data on the screen through the HD SDI output.

Finally, in the case of the Fujinon Cabrio I have had the pleasant surprise of seeing that the camera automatically recognizes it, so no mapping is necessary on any of the 3 axes. In addition, if we have a camera with an active mount (Alexa XT, Alexa Mini, Amira, Sony F55) the zoom servo will be powered from there, so we will only need 2 motors to control the 3 axes. I can definitely tell you that once again ARRI offers us a product of great quality, durability and with an extremely intuitive and “foolproof” menu.