Lights Camera Action!

Really? A blog about light—why? Well, we’re glad you asked. Light is essential for many reasons, especially as it relates to surveillance cameras. No matter your lighting situation, there is definitely a camera solution for your business. Read on to learn more about light and how it impacts picture quality. Consider yourself enlightened!

 

 

What is Light?

Simply light is the spectrum of energy that humans or cameras can “see”.  Webster defines light this way.

 

light noun \'līt\

 

: the form of energy that makes it possible to see things : the brightness produced by the sun, by fire, a lamp, etc.

 

: a source of light (such as an electric lamp)

 

: a light on a vehicle

 

Light has color and temperature.  Everyone is familiar with a rainbow. White light (from a source like the sun) contains all of the colors of light. It can be broken up by a prism you get to see the different colors available.  The color of an object is determined by what colors of light it reflects.  The temperature of light is measured in degrees kelvin. The “hotter” the light, the more blue it appears to the human eye, bright sunshine at noon (5600K) and florescent lights have high temperatures. the cooler the light temperature, the more it will be yellow or amber. Candles, sunsets (2500K) and incandescent (but not for long) light bulbs are all cooler in temperature. This can be counter intuitive as we commonly refer to orange and reds as being warm and blues as being cool.

 

 

What effect does light have on CCTV?

Light is the number one external factor in CCTV. Light comes from a light source like the sun or a light fixture, then bounces off the elements of the scene and is absorbed by the camera sensor. Without it you don’t get a picture.  A well-lit scene yields more vivid colors, higher detail and more clarity. Just like the human eye, the sensor in video cameras works better with more light. A dimly lit scene can still yield an effective image, but usually with more video noise and fewer colors or details.

 

Cameras have to have some light to function, they cannot see in complete darkness.  They will often have a lux rating, showing you how effective the are in low light situations. There are very high end cameras that can see the thermal spectrum, but they are uncommon in standard CCTV installations.

 

 

How does a camera turn light into a picture?

First, the lens on the camera gathers and focuses the light. Much like your eye, cameras  have a photo electric panel called a sensor. These sensors are usually one of two types, Charged Coupled Display (CCD) or Complimentary Metal-Oxide Semiconductor (CMOS). Don’t worry, there isn’t quiz at the end. These sensors change light into electronic signals that can be recorded by the DVR or NVR.

 

 

How does a camera control the amount of light it receives?

All cameras have an iris. The iris is a small hole in the lens that can be adjusted, a larger iris lets in more light while a smaller iris reduces the amount of light that reaches the sensor. In brightly lit scenes, an iris keeps too much light from reaching the sensor, this keep the image from being washed out or turning completely white. In a darker scene, the iris is opened, letting in more light.

 

Cameras have one of three types of irises, fixed, manual or automatic. A fixed iris is preset by the factory and cannot be changed. A manual adjustable iris can be adjusted by a technician, usually there is a dial or lever on the side of the camera to make these adjustments. An automatic iris or auto-iris, dynamically changes based the available light. All three can be used effectively in certain situations.

 

The speed of the camera’s shutter also plays a role. The faster the shutter speed, the shorter duration of light reaches the cameras sensor. This is good for high speed photography like sporting events. Slower shutters are good for scenes where the action is slower and a better picture quality is desired. The slower the shutter the more light reaches the sensor.

 

If you experience trouble with color temperatures, (usually manifesting in a bluish or amber looking image) you can adjust a camera’s white balance. This changes the way the camera interprets light and adjust the color accordingly.

 

 

Why do my cameras turn black and white at night?

Many cameras have a day/night feature. When the available light drops below a certain level, the camera automatically switches to a higher contrast, black and white image. This gives a better picture as the color noise is reduced. If you find that the feature turns on too soon or you would prefer color to the black and white image the feature can be disabled on most cameras.

 

 

Are there special cameras to deal with difficult lighting situations?

Absolutely.  The right camera can help you overcome a challenging lighting situation.  Here are a couple examples.

 

Say you have an area of high contrast, where sunshine is coming in through a door or window but the person you want to see is not as bright.  A WDR or Wide Dynamic Range camera takes two exposures (like taking two different pictures) of the scene then normalizes them. The result, a clear image of both the subject and the back ground.  This feature is especially effective in doorways and drive thru windows.

 

What if you have a room with all the lights off? In this case a camera with built in IR (Infra –Red) illuminators would be perfect. You can turn the lights off and the tiny IR illuminators project enough light to allow for an image.  IR does have a couple of limitations. Because it is outside the spectrum of light (remember the rainbow) that a human can see, it cannot be used as for other purposes.  IR always yields a black and white image and it has a short “throw” distance making it not effective in larger rooms or parking lots.  There are cameras that have an LED Flash (like your cell phone) that is visible (white) light.

 

If you are facing a challenging lighting situation, contact an iTech Digital account manager for more information on what CCTV products are right for you.

Ashley Schalk
buyers-guide.png
Which video surveillance system is right for my organization?
Video surveillance has several benefits, but designing the right system for your organization can be complicated. Take a crash course in the technology and terminology in our buyer’s guide to video surveillance systems.
Download the buyer's guide
  • Share:
Back to the blog