for Correcting White Balance Problems Using the Enosoft DV Processor
The Enosoft DV Processor features a powerful Processing Amplifier (Proc Amp) together with both Vectorscope and Waveform Monitor displays. With these tools, a multitude of problems can be corrected including Brightness, Contrast, Phase/Hue/Tint and White Balance.
Incorrect white balance is probably the most common problem and, traditionally, the correction takes place in post-production. The unique design of the Enosoft DV Processor allows the correction to be applied either at the time of capture or in post-production. If the original recording is made directly to disk on location, then the correction can be applied in real-time, on location.
Many camcorders permit some adjustment of the white balance but often this is in the form of preset values for common lighting environments, e.g., outdoors on a sunny day or indoors using incandescent lighting. Consequently, the camcorder's white balance setting may not be correct. This is especially true in mixed lighting environments where two or more types of lighting are used, such as incandescent light bulbs and fluorescent tubes.
When the white balance is not set correctly, the video image will appear to have a color cast, e.g., the image will appear too reddish-orange or too bluish-green. In particular, objects that are pure shades of grey will appear to have some color. The goal of white balance correction is to adjust the balance of the color components in the video so that greys and whites appear without any color.
For multicam shooting, ensuring the white balance settings for each camcorder are the same is also important otherwise different angles of the same scene may appear to have different color casts.
For this How-To article, a single camcorder is set up to record an indoors scene where both incandescent and fluorescent lighting are used. It is assumed that the video will be recorded to tape and transferred to disk later on.
Set the camcorder up in the desired location and, if possible, select the nearest white balance setting for the lighting conditions.
Either - Shoot a white target - this can be a white object placed somewhere in the field of view. However, you will have to temporarily zoom in on the object so that it fills the frame.
Or - Place a colorless, translucent object directly in front of the lens. Commercial devices do exist, however a plastic lid from a coffee can (or similar) will work.
With this "diffuser" in place, record a few frames. You will use this later when correcting the white balance.
Record the scene.
Launch the Enosoft DV Processor and configure it to display the video you previously recorded - i.e., the Input should be your camcorder/player and the Output should be the Video Renderer. Make sure the Processor is running (i.e., the incoming video is being shown in a second window).
Locate the portion of the recording made in Step 2. Put the camcorder/player in Pause mode and open the Proc Amp configuration dialog box:
In the Proc Amp dialog box, make sure the Vectorscope is enabled. Visually, the image appears to have a greenish-blue tint. The Vectorscope confirms this:
The green spot represents the color in the video signal and, in this case, lies off-center towards cyan (CY). The goal is to adjust the video signal such that the green spot in the Vectorscope display falls directly in the center.
The Vectorscope display is a obtained by plotting the Cr component against the Cb component. Hence, to center the color information, both the Cr and Cb components need to be offset by some amount. To do this, enable both the Cr and Cb sliders in the Proc Amp dialog box and adjust the two Offset sliders to move the green dot to the center of the Vectorscope display. (The Cr Offset slider will move green dot up and down, the Cb Offset slider will move it left and right).
The video in the Renderer window should now appear grey/white:
Release the camcorder/player from Pause mode and view the recorded scene:
Optionally, you can use the Split Screen function of the Proc Amp to compare the processed (left) and unprocessed (right) video in the output window:
As can be seen, the concrete floor in the scene appears much more natural (grey) and the wooden doors have a much richer tone.
Stop the camcorder/player and,optionally, save the Proc Amp settings (Save... button), making sure that the Split Screen is turned off.
Close the Proc Amp dialog box and stop the Processor.
Change the output to be an AVI file.
Start the camcorder/player and then set the Processor running to capture the video. The captured video will be a corrected version, according to the settings of the Proc Amp.
Stop the Processor when you have captured the desired portion of the video from the camcorder/player.
APPLYING CORRECTION AT THE TIME OF RECORDING
The above example assumes that the video has been recorded on tape and is subsequently transferred to the computer. However, you can save a lot of time by performing the correction at the time of recording.
There are two ways to do this depending upon whether you have a second DV device or not.
1. Direct to disk
If you want to record directly to disk, follow the above procedure but use the live feed from the camcorder as the input.
2. Live correction to tape
With a single camcorder, it is not possible to correct the video signal and record it on tape in real time. With two camcorders (or a DV recorder), this is possible and provides a great deal of flexibility.
The camcorder recording the scene is configured as the input device for the Enosoft DV Processor and the second DV device is configured as the output device.
Make sure the Processor is running. Use the Proc Amp to make the necessary adjustments and, when ready, start the output device recording. You may also wish to have a tape in the input camcorder, too, so that you have two tapes - one corrected and one uncorrected.
With this scheme, no disk space is required and you avoid the risk of dropped frames during capture to disk.
Furthermore, with a video monitor connected to the output device, you can see exactly what the output device is recording.
In effect, when used in this mode, the Enosoft DV Processor is acting like a stand-alone hardware Proc Amp between two DV devices.
This configuration is shown schematically below:
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