3 Camera Q. What is ICR, TDN, and DDN? 2013-04-28

ICR (Infrared Cut Filter) is used with color CCD or CMOS image sensors to produce accurate color images. During the day, the camera uses an ICR to reflect or block mid-infrared wavelengths while passing visible lights. However, as light diminishes below a certain level, some cameras can automatically turn off ICR functionality to deliver high-quality, black and white image using infrared light.

TDN (True Day/Night) technology supports night vision capability by implementing a physical ICR that is removed by a mechanical motor.

DDN (Digital Day/Night) technology allows for viewing in both day and night conditions, without the use of a ICR. As light diminishes below a certain level, DDN technology switches color image to black and white image to offer similar benefits to TDN with a lower cost. At night, the captured image depends on the lighting and infrared waves off objects.
2 Camera Q. What is DOF? And, What is difference between deep DOF and shallow DOF? 2013-04-28

DOF (Depth of Field) refers to the range of distance that the subject appears acceptably sharp. DOF is determined by several factors such as aperture size, lens to subject distance, lens focal length, and image sensor size.

Generally, the following conditions result in a deep DOF.

- small or narrow aperature size (large f number)

- long distance between lens and subject

- short focal length

- small image sensor size (small image format)

A shallow DOF has reverse condition of a deep DOF.
1 Camera Q. What about indoor vs outdoor models? what are the main differences? 2013-04-28

Surveillance cameras can be classified as indoor and outdoor models according to installation place. The main difference between two models is whether the camera is weather-proof or not. That is, outdoor camera does completely protect the inner material from weather like wind, rain, moisture, dust, snow, and humidity. Some outdoor cameras should have heater or blowers for temperature resistance. On the other hand, indoor cameras do not require weather-proof or temperature resistance except critical places which get high humidity or high/low temperature.

In addition, outdoor cameras require infrared or TDN (true day/night) technology more than indoor cameras for night vision capability.