Have you ever looked at the LCD screen of a camera in a bright room and thought that the image was very dim or under-exposed? Or have you ever seen the same screen in a dark environment and thought the image was over-exposed? Ironically, sometimes the resulting image is not always what you think it will be.
"Exposure" is one of the essential skills for shooting videos. Though users can use image-editing software to make adjustments in post-production, managing correct exposure can help the videographer get high-quality images and avoid spending excess time in post-production. To assist videographers in monitoring image exposure, many DSLRs have built-in functions to monitor exposure. For example, the Histogram and Waveform are handy tools for professional videographers. In the following article, we are going to introduce the standard functions for getting correct exposure.
Histogram Scope is composed of an "X-axis" and a "Y-axis." For the "X" axis, the graph's left side represents the darkness, and the right side represents the brightness. The Y-axis represents the pixel intensity distributed throughout an image. The higher the peak value, the more pixels there are for a specific brightness value and the larger area it occupies. If you connect all the pixel value points on the Y axis, it forms a continuous Histogram Scope.
For an overexposed image, the histogram's peak value will be concentrated on the right side of the X-axis; conversely, for an underexposed image, the histogram's peak value will be concentrated on the left side of the X-axis. For a properly balanced image, the histogram's peak value distributes evenly on the center of the X-axis, just like a normal distribution chart. Using the Histogram Scope, the user can evaluate whether the exposure is within the correct dynamic brightness and the color saturation range.
The Waveform Scope shows the luminance and RGB & YCbCr values for the image. From the Waveform Scope, users can observe the brightness and darkness of the image. The Waveform Scope converts the bright level and the dark level of an image to a waveform. For example, if the "All Dark" value is "0" and the "All Bright" value is "100", it will warn users if the dark level is lower than 0 and the brightness level is higher than 100 in the image. Thus, the videographer can better manage these levels while shooting video.
Currently, the Histogram function is available on entry-level DSLR cameras and field monitors. However, only the professional production monitors support the Waveform Scope function.
The False Color is also called "Exposure Assist." When the False Color Function is on, an image's colors will be highlighted if it is over-exposed. So, the user can examine the exposure without using other expensive equipment. To fully realize False Color's indication, the user must understand the color spectrum shown below.
For example, in areas with an exposure level of 56IRE, the false-color will be shown as pink color on the monitor when applied. Therefore, as you increase the exposure, that area will change color to grey, then yellow, and finally to red if overexposed. Blue indicates underexposure.
The "Zebra Pattern" is an exposure-assisting function that is easy to understand for new users. Users can set a threshold level for the image, available in the "Exposure Level" option (0-100). For example, when the threshold level is set to "90", a zebra pattern warning will appear once the brightness in the screen reaches above "90", reminding the photographer to be aware of the image's overexposure.