¶ Introduction
DCS' LDT-M2 is a lens encoding system for the Arri ALEXA Mini, Mini LF and ALEXA 35. It reads the Focus, Iris and Zoom motor movements and translates this information into compatible data for the host camera. This metadata is then written directly into the ArriRaw camera files in real time.
Please note: LDT-M2 requires a connection to the camera through the LBUS on the lens mount. If a lens mount is being used which does not have the LBUS port the LDT-M2 cannot record metadata. If this is the case contact DCS and ask about the LDT-V1 which can record the lens data on an SD card.
Please note: LDT-M2 works with the Preston system but in order to create a lens table a WCU-4 or Hi-5 handset is required.
LDT-M2 Compatibility:
- Preston MDR3/MDR4
- Preston HU3/HU4
- ALEXA Mini/Mini LF
- ALEXA 35
Please contact DCS for more information if your device is not listed here.
¶ LDT-M2 Components
The CAM port is labelled LBUS on later models.
| 1 | ETH | 5-pin 0B Lemo | |
| 2 | ENC | 6-pin 0B Lemo | |
| 3 | SERIAL | 4-pin 0B Lemo | |
| 4 | MDR | 4-pin 0B Lemo | |
| 5 | CAM (LBUS) | 4-pin 0B Lemo | |
| 6 | CAL | Calibration Button (LDT-E Series Only) |
¶ Physical Connections
| Name | Type | Description | Cable Codes |
|---|---|---|---|
| ETH | 10-pin 1B Lemo | Ethernet to RJ-45 computer connection | ETHA |
| ENC | 6-pin 0B Lemo | Lens data encoder connection port for LDT-E1 | ENC |
| SERIAL | 4-pin 0B Lemo | Serial passthrough connection port | CT |
| MDR | 4-pin 0B Lemo | Preston MDR Serial connection port | MDR, MDRP |
| CAM (LBUS) | 4-pin 0B Lemo | LBUS connection to camera | LBUS |
¶ Cable Types and Codes
All DCS cables are categorized using a code and a bend relief color for each of the cable types. Cables have two default lengths, 12 or 18 or 24 inches and the connector type can be straight (S), right angle (R), or anglissimo (O). Custom cables can be made upon request.
| Code | Bend Relief Color | Type Port Name |
Description |
|---|---|---|---|
| ETHM | Black | 10-Pin 1B Lemo to RJ-45 ETH |
ETHA cable connects the LDT-M2 to a computer for firmware updating. |
| CT | Orange | 4-pin 0B Lemo to 6-pin 1B Lemo SERIAL |
CT cable connects the Preston MDR3/MDR4 serial port with a CineTape. This cable connects to the LDT-M2 Serial connector if the Preston MDR serial ports are in use. |
| MDR | Blue | 4-pin 0B Lemo to 4-pin 0B Lemo MDR |
MDR cable connects the LDT-M2 to a Preston MDR3/MDR4 serial port. |
| MDRP | Blue | 4-pin 0B Lemo to 4-pin 0B Lemo MDR |
MDRP cable connects the LDT-M2 to a Preston MDR3/MDR4 serial port. Also provides power. |
| LBUS | RED | 4-pin 0B Lemo to 4-pin 0B Lemo CAM |
LBUS cable connects LDT-M2 to the LBUS port of the ALEXA Mini / Mini LF camera. It injects the encoded data into the RAW file. |
| ENC | Green | 6-pin 0B Lemo to 6-pin 0B Lemo ENC |
ENC cable connects the LDT-E1 to the LDT-M2. Look at Using a Lens Data Encoder |
¶ Updating the LDT-M2 Firmware
The LDT-M2 should come up-to-date with the most recent firmware. If you need to check the firmware or update for some reason please get in contact with where you rented the LDT or DCS.
If you are from a rental house and are looking for firmware update information this can be found in the LDT-Tester manual on the rental house support site here.
¶ Rigging the camera
Incorrectly connecting the LDT-M2 can damage the unit. The LBUS port of the camera should never be connected to the MDR or SERIAL ports of the LDT-M2. Follow all instructions below carefully.
For the ALEXA 35 connect the LBUS cable (red) to either of the LBUS ports on the front of the camera. If either port is not operational please contact the camera rental house.
- Mount the LDT-M2 to the camera,
- Connect the MDR port of the LDT-M2 to a Serial port on the Preston MDR using the blue booted MDRP cable,
- Connect the LBUS (CAM) port of the LDT-M2 to an LBUS port on the camera using the red booted LBUS cable,
- Rig the Preston and Preston motors in the way they will be used on the day,
- Calibrate Preston motors (check Preston calibration method here).
If using an LDT-E series with a Preston, these are calibrated by the same command as the Preston.
If not using a Preston and only the LDT-E series encoders - calibration is done from the blue button on the LDT-M2 (see here).
¶ Setting up the Preston MDR
It is essential to update all Preston firmware.
Use an MDR-3 for building lens tables (MDR4 can be used for normal operation if required).
Disable F-Maps on the HU3/HU4 when building lens tables on the camera (F-maps can be used during normal operation).
Setup the Focus / Iris / Zoom direction for normal use on the Preston handsets.
During lens table building the hand unit must be turned off and the WCU-4/Hi-5 will control the Preston Motors.
¶ Calibrating the Preston with the LDT-M2
¶ Initial or Reboot Calibration
On powering up or reboot, calibration of the Preston motors needs to be done from the camera:
- Alexa Mini LF:
Menu > ECS > Calibrate All Motors - Alexa 35: Menu
Lens & ECS > Calibrate All Motors
¶ Routine Calibration
There are currently 2 firmwares in circulation that require a different action from the user to calibrate the Preston motors.
If running Firmware 2.09 or below - calibrate the Preston from the blue button on the LDT-M2.
If running firmware 2.10 or above - calibrate the Preston from MDR as normal.
¶ Using a Light Ranger with the LDT-M2
The LDT-M2 is equipped with a serial loop through port. Connect the Light Ranger device to the serial port of the LDT-M2 instead of directly to the MDR.
There is a known issue between the Light Ranger, MDR4 and LDT-M2 where data will not show up. If this happens, unplug and replug the Light Ranger from the LDT-M2 serial port and this will solve the issue. Please repeat if it does not work the first time.
¶ Settings for the Arri ALEXA Mini/Mini LF
The Camera’s internal lens mount must be disabled in order to use the external LBUS connector.
-
Choose
MENU > System > Lens data > Lens Mount Settings -
Untick
Enable lens mount -
Change
Focus unittoImperial
¶ Settings for the Arri 35
The Camera’s internal lens mount must be disabled in order to use the external LBUS connector.
-
Choose
MENU > Lens & ECS -
Untick
Enable lens mount -
Change
Focus unittoImperial
¶ Overlay Lens Data on a Monitor (Mini/MiniLF/35)
In order to display lens data as an overlay on an SDI monitor, do the following:
- Choose
MENU > Monitoring > SDI > SDI processing > Overlays > Status Components - Tick on
Lens dataandLens Focus Distance.
¶ Overlay Guide
¶ Mini LF
¶ Programming a New Lens Table
Lens tables can be created on one camera and shared to other cameras. If using a mix of large body and mini ALEXAs, DCS recommends making the lens tables using the large body ALEXA camera and LDT-A2. Instructions on how to transfer the lens tables via SD card for the large body can be found here and via USB for the Mini can be found here.
Creating a lens table is essential to the encoding process. It requires inputting the relevant lens information (lens name, brand, serial number etc.) and then inputting all of the marks from each axis (focus/iris/zoom) for each lens. The following guide explains this process.
If existing tables have been made on the camera without the LDT, new ones will need to be made. Editing the existing tables can lead to errors.
¶ Mapping Mode on the LDT-M2
If the LDT-M2 is running firmware 2.11 or later then it will need to enter ‘mapping mode’ before lens tabling.
If the LDT-M2 is running firmware 2.10 or below then it is constantly in mapping mode and does not require the settings below. If this is the case and a WCU-4 or Hi-5 will be used on set to control camera settings please read this section.
Mapping mode on the LDT-M2 allows a WCU-4 or Hi-5 to control the Preston motors whilst in this mode.
To enter mapping mode:
- Hold the blue button on the LDT-M2 for 10 seconds.
To exit mapping mode:
- Power cycle the LDT-M2 by unplugging and replugging the LBUS cable.
Mapping mode should only be used when making lens tables - during normal operation this mode should not be used.
¶ Creating a New Lens Table
If using F-Mapping on the Preston Hand Unit, build the F-maps first then move on to the lens table process. This is to avoid any conflicts with motor directions.
Mapping a new lens table is crucial to ensuring that the data encoded throughout the production is precise.
When mapping a lens, a methodical process needs to be adopted. As standard practice, DCS suggests to enter a mark point on the WCU-4/Hi-5 for each engraved mark on the lens and let the LDS system interpolate the rest of the data.
Ensure that the lens calibration happens without any motor slip. When moving the lens axis with a remote handset, mark alignment should always be achieved from the same direction to avoid slack on the lens.
¶ Initial Set-up
- Enter mapping mode on the LDT-M2 (if using firmware 2.11 or above) Link,
- Turn off F-mapping on the Preston Hand Unit,
- Turn off the Preston Hand Unit,
- Ensure the WCU-4/Hi-5 has an SD card inserted,
- Turn on the WCU-4/Hi-5,
- Connect to the camera,
- Calibrate the Preston motors (see here for more details).
The WCU-4/Hi-5 should now be controlling the Preston motors.
¶ Preston Motor Rigging
Motors should be rigged as they will be used during filming. Jump to Adding a New Lens.
There is a known issue with motor positions and lens table building on the ALEXA 35 and on the ALEXA Mini LF when running firmware 7.3. Please read the following carefully.
¶ ALEXA 35/Mini LF 7.3 Motor Rigging for Lens Table Issue
If encountering an issue when building lens tables on the WCU-4 or Hi-5 where the span of the lens table on the handset is short (i.e. start and end points are very close) and do not allow for additional points to be added follow these steps:
-
Cancel the current table,
-
Ensure all motor directions on the MDR are normal (lights on the MDR OFF),
-
For the affected axis:
-
Physically flip the motor on the same bar so the cog will now be reversed
-
For example:
Original Rigging
Flipped rigging -
Calibrate from the camera: Menu
Lens & ECS > Calibrate All Motors -
Restart the lens mapping process.
Note - the motor must be manually flipped. Using the camera or MDR flip settings will not work.
Once lens tabling is complete the lens motors can be returned to their preferred position.
If there are any issues with values being reversed then reverse the motor direction in the Alexa GUI:
Choose MENU > Electronic Control System (ECS) > LBUS lens motor configuration
A workaround for this issue on the ALEXA Mini LF is to revert the firmware to either 7.1.2 or 7.2. Once the lens maps are created, the camera can be updated to 7.3 and make use of the newly made .tab files.
¶ Adding a New Lens
Mount a new lens to the camera. Calibrate the Preston (Check Preston calibration method here). On the WCU-4/Hi-5
Choose MENU > LENS DATA > LENS PROGRAMMING > CREATE LENS FILE
Select the lens brand, it can either be selected from a list or added manually. Use the up and down buttons to select from the list, or select custom to enter a custom lens brand name. Press OK or the user button to confirm the selection.
To enter a custom brand lens use the zoom stick to select characters on the left hand side of the screen. In order to select a character press the user button. In order to delete a character press the delete button. When finished press the OK button to select the lens type.
To select a focal length use the up and down buttons or the zoom stick to navigate the list. In order to enter a custom focal length press custom. For a zoom lens select zoom and then press OK or user button to confirm.
To enter the lens serial number use the zoom stick to highlight a number and press the user button to select it. Press the delete button to delete the last number. Press the OK button once the serial number is complete.
Select the unit of measurement for focus, use the up and down buttons or the zoom stick to select metric or imperial and then press the OK or User button to confirm.
¶ Mapping a Lens Table
Once all the lens information is entered, select either ‘Focus’, ‘Iris’ or ‘‘Zoom’ (if a Zoom lens is being used) axis to start mapping the lens.
During mapping, if the lens table for the specific axis is not allowing values to be added, then it is likely the motor directions will need to be altered for mapping. Please refer to the instructions here.
¶ Mapping the Focus Axis
Use the focus knob to move through the span of the axis, ensuring that it reaches each end of the lens. If not, check if there were any slips during calibration.
To programme the focus scale press the focus button.
To set the infinity mark for focus rotate the focus knob until the lens reaches infinity. Press the OK or user button to set the infinity point.
To set the close focus mark. Rotate the focus knob until the lens reaches closed focus. Use the up and down buttons or zoom stick until the close focus value appears on the screen. Press the OK or the user button to confirm. Now repeat the above steps in order to populate your lens table. Work through each engraved value on the lens to ensure maximum precision. Use the Down button to edit any data points.
Once all focus values have been entered press finish to save. Press OK to return to the Select Axis Screen.
¶ Mapping the Iris Axis
Use the iris slider to move through the span of the axis, ensuring that it reaches each end of the lens. If not, check if there were any slips during calibration.
Now move onto mapping the Iris by pressing the Iris button.
Set the iris to wide open. Use the up and down buttons or the zoom stick to select the open iris value. Press the OK or User button to confirm.
Now work through the rest of the Iris marks. Move the iris slider to the next engraved mark on the lens and press the OK or user button to confirm and repeat until all the desired marks are entered.
When finished press the OK button or the Finish button
¶ Mapping the Zoom Axis
If encoding a zoom lens press the Zoom button.
Use the zoom stick to move through the span of the axis, ensuring that it reaches each end of the lens. If not, check if there were any slips during calibration.
Use the iris slider to move the zoom axis. Set the zoom to its widest zoom mark then use the up and down buttons or the zoom stick to set the wide focal length on the handset. Press the OK or User button to confirm the focal length.
Move the zoom scale to the next focal length mark. On the handset use the up and down buttons or zoom stick to set the focal value length. Press the OK or User button to confirm the value. Repeat for the rest of the focal length points.
After entering all focal length points, press the OK button to return to the Select axis screen.
¶ Saving a Lens Table
Once completed press the OK button to return to the Select Axis Screen.
To save the lens table, first be sure to insert an SD card into the WCU-4, then press the Save button. The file will be saved on the folder/ARRI/ALEXA/LDA.
It is possible to change the name of the lens that will be displayed on the camera or motor controller before finally saving onto the SD card. This name will also be the name of the lens file. Press the Mode button and select insert, overwrite or delete a character. Press the Save button when happy with the name to save it to the SD card.
¶ Edit a Lens Table
An existing lens table can be edited with the WCU-4 hand unit and then stored back on an SD card. Load the lens file to edit onto an SD card in the (folder /ARRI/ALEXA/LDA) and insert the SD card into the SD card slot of the WCU-4.
Go to MENU > LENS DATA > LENS PROGRAMMING > EDIT LENS FILE
Use the UP and DOWN soft buttons or the zoom stick to scroll through the list of lens files on the SD card. Press the SELECT soft button or the User button to select a lens file.
On the following screen, use the FOCUS, IRIS or ZOOM soft button to select the lens scale to edit. If metric and imperial scales exist, select the scale unit first.
The following screen provides three different options (OFFSET, SLIDE, SNAP) for editing existing data points.
¶ Offset Function
Use the OFFSET soft button to correct a fixed offset between the complete lens scale and the corresponding scale on the WCU-4 screen:
Select a reference witness mark on the WCU-4 display (e.g. infinity).
While keeping the OFFSET soft button pressed, drive the lens scale to the corresponding witness mark.
Release the OFFSET soft button when lens scale and display scale match.
¶ Slide Function
Use the SLIDE soft button to correct an offset for a single data point:
Select the witness mark to edit on the WCU-4/Hi-5 display.
While keeping the SLIDE soft button pressed, drive the lens scale to the corresponding witness mark.
Release the SLIDE soft button when lens mark and display mark match.
¶ Snap Function
Use the SNAP soft button to correct a slight offset for a single data point. The snap function will move the nearest available data point on the WCU-4/Hi-5 screen to the currently set lens position:
Drive the lens scale to a witness mark.
Press the SNAP soft button. The nearest available data point on the WCU-4/Hi-5 screen will jump to the currently set position.
Press the RESET soft button to reset all editing actions.
Press the BACK soft button to apply all editing actions and return to the Select Axis screen.
Press the SAVE soft button to save the lens file to SD card folder /ARRI/ALEXA/LDA. You can edit the lens name before saving.
¶ Using a Lens Data Encoder (LDT-E Series)
Camera operators may wish to manually control the zoom instead of using a motor. A lens encoder can be used instead of a motor allowing the axis to spin freely whilst still providing the LDT-M2 with zoom data.
DCS provides a lens data encoder called LDT-E1. This device is plug and play, and does not require additional or separate lens tables to work.
A video tutorial explaining the set-up of the LDT-E1 can be found here
To use the LDT-E1:
Rig the LDT-E1 to the zoom axis,
Select “z” on the LDT-E1 using the physical button,
Connect the ENC cable to the port of the LDT-E1 and the ENC port of the LDT-A2.
The LDT-E1 can also be used to send focus or iris data to the LDT-M2 if required. Simply rig the encoder on the desired axis and change the physical button to that axis.
Note: the direction of the motor might need to be reversed: please go to the Changing the Motor Direction chapter.
¶ Setting the axis for the LDT-E1
Select an axis using the switch on the LDT-E1 to bound data correctly.
For example:
- Rig the LDT-E1 to the zoom axis,
- Connect the LDT-M2 and the LDT-E1 using the ENC cable.
- Select z on the LDT-E1 using the physical button,
The LDT-E1 can also be used to send focus or iris data to the LDT-M2 if required. Simply rig the encoder on the desired axis and change the physical button to that axis.
To calibrate the LDT-E1, press the calibrate button on the MDR. Then rotate the desired axis from one extreme to the other pausing for one second at each end.
¶ Using Multiple LDT-E Series Encoders
The LDT-E1 can be daisy chained with additional LDT-E2 encoders to deliver all lens axis data to an LDT-M2.
¶ Calibrating Only LDT-E Encoders
If solely using LDT-E series encoders with no Preston system, calibration is done by:
- holding down the blue button on the LDT-M2 for 3 seconds,
- manually rotating each axis from end to end.
¶ Changing the Motors direction
If for rigging purpose a lens motor or lens encoder needs to be reversed:
- Choose:
Menu > ECS > LBUS Lens Motor Configand select Right or Left on one of the axes.
¶ Transfer a Lens Table
¶ Transferring wirelessly from WCU-4/Hi-5
Users can select a lens file stored on the SD card in their WCU-4/Hi-5 and using just the hand unit wirelessly transmit the file to the ALEXA Mini, saving time and effort.
To transfer a lens file, insert the SD card with lens files on it into the SD card slot of the WCU-4/Hi-5:
- Go to
MENU > LENS DATA > LENS FILE TRANSFER - Select
LENS FILE TRANSFER
Use the UP, DOWN and SELECT soft buttons or zoom stick and User button to navigate through the folder structure on the SD card and select a lens file.
Press SEND to transmit the lens file wirelessly to the camera device. The transferred lens file is activated immediately.
¶ Transferring via USB
If the lens file transfer does not work wirelessly then you need to use a computer to transfer the lens files. Connect a USB to the ALEXA Mini to format it first and generate the correct file structure. Then, using a computer, copy the lens files from the SD card of the WCU-4/Hi-5 to the "LDA" folder on the formatted USB. Connect the USB to the camera and transfer the lens files.
Once the lens file has been transferred to the ALEXA Mini, switch off the WCU-4/Hi-5 and turn on the Preston Hand Unit.
It is recommended to test the the lens tables after transfer. Select a lens table and then check if the lens lines up with the lens data on the ECS or by using the monitor overlay.
¶ Selecting a Lens Table
The lens tables are recalled through the GUI of the camera:
- Choose
MENU > Electronic Control System (ECS) > Lens data > Clear - Choose
MENU > Electronic Control System (ECS) > Lens data > LDA - Select the Lens Table corresponding to the mounted lens and click
Use, - Calibrate the lens using the calibration button on the MDR.
¶ Using the WCU-4 or Hi-5 for Camera Control
The following settings are only required if using an LDT-M2 with firmware 2.10 or lower as 2.11 introduces a mapping mode to the LDT-M2 which means the WCU-4 and Hi-5 cannot talk to the LDT-M2 when it is not in mapping mode. More details here.
These WCU4/Hi-5 settings must be turned on in order for the hand unit to connect to the preston motors when using the encoding mode on the LDT-M2 unit (https://support.dcs.film/LDT-M2UserManual#mapping-mode-on-the-ldt-m2).
If a WCU-4 or Hi-5 hand unit is required for remote control of the camera during shooting it is essential that all motor controls are turned off to avoid disruption of the Preston units.
Please note - that these settings must be turned ON during initial set-up if the unit is being used to build the lens tables.
WCU-4:
- Choose:
Premarked Ring > None - Choose:
Control Setup > Slider > Off - Choose:
Control Setup > Stick > Off - Choose:
Control Setup > Knob > Off
Hi-5:
- Choose:
Premarked Ring > None - Choose:
Control Setup > Knob > Off - Choose:
Control Setup > Slider > Off - Choose:
Control Setup > Force-Pad > Off
¶ Shooting a Test
When shooting test footage, allow approximately one hour per camera type being used on the production. A test will involve recording the metadata with a camera and recording a separate feed from the camera with an overlay to verify the data is correct at the final stage of the test. We recommend using a zoom lens (if any are being used during the shoot) in order to check all three axes.
- Rig and set-up the camera and LDT as per the instructions in this manual,
Do not run the camera without the LDT attached.
For Each test a written visual representation of the FIZ values is required, for instance a clapper board with the lens values written on it.
¶ Test One - Static Test (Prime or Zoom)
- Set each axis to a value e.g. T-Stop 4, Focal length 22mm, Focus distance 6ft,
- Write on the board the test number, the lens name, and the values of each axis,
- Record a 10 second clip
¶ Test Two - Static Test (Different Prime or Zoom)
- Set each axis to a different value than test one e.g. T-Stop 5.6, Focal length 45mm, Focus Distance 30ft,
- Write on the board the test number, the lens name, and the values of each axis,
- Record a 10 second clip
¶ Test Three - Racking Test (Zoom Lens)
- Set each axis to a value e.g. T-Stop 4, Focal length 22mm, Focus Distance 6ft,
- Write on the board the test number, the lens name, the static values of each axis, and the range of the span of each axis (e.g. Iris T1.8 - T22, Focus 16"-Inf, Zoom 15mm - 30mm)
- Record a clip,
- During the recording, rack each axis one at a time, starting at the static number rotating the axis from one end to the other and returning to the static number.
¶ Final Steps
- Extract the lens medatada from the ARRIRAW,
- Merge the extracted CSV files to the EXR,
- Compare the metadata of the EXR file to the overlay footage.