Racking and Vision Control

Racks and Vision Control in the Gallery

The aim of this document is to describe how to use the camera racking controls in the gallery. These controls allow you to adjust the colour balance and exposure of the cameras on the studio floor. These controls are only for the TV Studio cameras, any cameras that are brought in from elsewhere will have to have their colour balance and exposure set to match these cameras.

The topics covered in this guide include:

The camera channel.
Camera remote control (RCP-1000) overview.
Line up procedure
Black Balance
White balance
Exposure

The Camera Channel

In a direct contrast to the world of single camera productions, studio and live outside broadcast productions rely on the fact that you are shooting on multiple cameras that should cut together so the viewers are immersed in the action rather than being distracted by shots that don’t ‘match’ with regards to exposure or colour balance. With this end in mind the idea of having controls for all the cameras in one place starts to make perfect sense.

Using the three camera remote controls we have the ability to adjust all three cameras so they match up together and can be cut without any shot looking different to the others.

The camera channels we use consist of three elements. These are the camera, the camera control unit and the camera remote control. The Camera Control Unit or CCU feeds power to the camera and handles all the in between communications between the remote control unit and the camera body.

Camera Remote Control Overview

The camera remote controls or ‘Racks’ live in the gallery and allow you to control the exposure and colour balance of the three studio cameras from the vision engineering position in the gallery. When you’re trying to get all three cameras to match the best place to start is with a camera line up.

Auto White Balance
Auto Black Balance
Camera Number, red background if ‘on air’
Relative button. Determines if the Iris joystick controls over the whole lens range (off) or a subset (on)
Coarse & Sensitivity controls. Control the range of the iris joystick control.
Iris (Exposure) remote control. Black level on ring.
Panel Active button. (Must be lit to control the camera head.)

Camera Line Up

To perform a camera line up follow this procedure:

Setup the line up chart on a stand
Put a single tungsten (3200K) lamp on the chart
Ensure there is no reflections/glare on the chart
Physically line up all three cameras so they are pointing at the line up chart. Make sure the line up chart is well lit and in focus.
With the line up chart full frame make your way up to the camera remote controls in the gallery.

Prior to the line up, the chart needs to be correctly exposed so that the white chips (in the middle of the chart) are just touching the 100% (700mV) line on the waveform monitor and the gregory hole on the chart needs to have it's black level set so that it just touches the 0% (0mV) line on the waveform monitor.

(Note that the black chips at the end of either greyscale are not the same black as the gregory hole and therefore will not line up at the same level as the gregory on the waveform monitor, they should be approx 70mV)

Before performing the line up, the red and blue controls for the black and white balance should be set to their zero (12 o-clock) position, otherwise there will not be any room on the controls to adjust these afterwards manually once the ABB/AWB is done.

The joystick should be put to a vertical position and then the Coarse exposure control knob adjusted to bring the white levels to the correct level on the waveform monitor. This way you know you will have room to move open or close the iris once the line up is complete.

Performing the Line Up

Perform an ‘Automatic Black Balance’ by pressing the ‘ABB’ button on each remote. This will adjust the camera settings so that the black levels all line up correctly. You can use the RGB Parade scope to check this line up.
Once the ABB has been performed you can move onto the white balance. You can achieve a white balance in a very similar way to the ABB. Press the ‘Automatic White Balance’ (AWB) button on the remote.
Check on the RGB Parade scope to make sure the colour balance is correct between all three cameras.
You can now fine tune the exposure by using the joystick on the remote controls.

Black Balance

The term ‘Black Balance’ refers to how the camera perceives true black. If the black balance isn’t set correctly then the foundation that the camera builds it’s colour balance on will be skewed and correct colour balance from this point onwards will be tricky. It’s best to start your camera line up with black balance. To perform a black balance on the camera remotes you press the ‘ABB’ button, the camera will go black for a short period while it adjusts its settings to give a good black balance.

White Balance

Similar to black balance the white balance of the camera adjusts the colour balance to give a true white image. After you have performed the black balance procedure you can perform an Automatic White Balance by pressing the ‘AWB’ button on the remote. Doing this while the camera is focused on the line up chart means there is enough white in the camera to judge how the white section of the image should be adjusted.

Usually this leads to very good results but if you are still struggling to get a correct balance or you want to warm or cool the image you can use the red and blue rotary controls to adjust the red and blue channels of the image to create the desired effect.

After pressing the AWB button, if the button continues to flash and doesn't go out, the white balance has failed to complete which is normally due to the exposure of the white chips on the waveform monitor being too high or too small.

Exposure

The camera can change the amount of light getting to the sensor by adjusting the exposure. There are three variables that affect exposure. The first two are shutter speed and gain. The shutter speed is set in camera and we have set the studio cameras shutter speeds so they don’t flicker on in vision screens. The gain is set on the remote control and you can adjust this in 3db amounts. Usually you would try to keep gain to a minimum but if you are really struggling for exposure then you may want to think about adding gain.

However the main control and the place where all exposure settings should be started is the adjustment of the iris. This is done on the remote control by moving the joystick up to increase the exposure or down to reduce the exposure.

Written by RW

Report abuse