When a surveillance camera is installed, you want to know that the images it captures will be crisp, clear and useful. To get the most from video surveillance, it’s important to understand the basic factors that contribute to good image usability. Learn how light affects exposure settings and contributes to image quality to guarantee that your images always look sharp, never fuzzy.
Here are five imaging principles you can use to ensure ideal image quality from your video surveillance system.
1. Adapt to Any Type of Light
The sun rises in the morning and travels across the sky during the day, changing the direction of light. It’s always a good idea to have the sun behind the camera, not in front of the lens. This avoids potentially blinding backlight situations. Clouds and bad weather conditions affect the intensity of sunlight, creating a need to change exposure settings in the camera. The time of day affects the color of sunlight, also referred to as the color temperature. Sunlight is neutral at midday and changes to warm, intense colors at sunrise and sunset. All of these light parameters affect how images are perceived in video surveillance. Light direction, light intensity and color temperature need to be correctly handled to ensure sharp images in any type of light.
2. The Right Exposure in Rain or Shine
In bright daylight, each scene holds a lot of light energy. More light means less exposure is needed. A well-illuminated scene doesn’t need to be exposed through the lens element and onto the sensor for very long to achieve the required exposure value. On the other hand, each scene holds less light in cloudy weather. That means the scene needs to be exposed through the lens element and onto the sensor for a longer period of time.
An alternative to achieving the correct exposure value is increasing the iris opening. A camera iris is an aperture that adjusts to control the amount of light coming in through a lens. This lets more light flow into the camera per unit of time. If you choose to increase the iris opening, keep in mind that:
- short exposure times limit motion blur, and,
- small iris openings increase depth of field.
3. Stay Focused With Depth of Field
If the outside scene is sunny, the iris opening can be reduced. Partly closing the iris improves your depth of field, or the distance between the closest and farthest objects that can be in focus. Zooming in on an object greatly limits the surveillance opportunities in the surrounding areas. If you simultaneously zoom in and have the iris fully open because light is limited, the depth of field is reduced further.
4. Understand Pixel Size and Detail
When comparing camera sensors, it’s clear that the finer the pixel grid, the better it recreates details in a surveillance scene. Generally, a larger sensor can gain more information and produce clearer images than a smaller one. Larger sensors are also typically more expensive. But when you compare a low-resolution image that offers only an outline to an image showing finer details from higher-resolution cameras, the advantages speak for themselves. Consider the level of detail you need from your video surveillance system when choosing a camera.
5. Better Lighting With Wide Dynamic Range
A scene that holds great variances in contrast requires separate exposures to offer full detail in both dark and light areas of the scene. As the exposure time increases, more of the details in darker areas become visible. "Wide dynamic range" is a feature that allows objects in light and dark areas to be observed. With this feature, the camera takes two exposures of the full scene. These are then merged together to achieve the final result, offering a wider dynamic range.
The Path to Better Image Quality
Understanding depth of field and exposure value will help you capture clearer images with your video surveillance system. Not all surveillance cameras are made equal, but by using these imaging principles, you can be on the path to clearer, sharper images.
The opinions expressed in this piece are solely Axis’. They do not necessarily represent WESCO’s views.
Check out another related article from Axis: How to Give Your Customers a First-Rate Video Surveillance System