July 10, 2012

How Important are Auto Iris and Wide Dynamic Range in CCTV?

In our last blog post we discussed the need to accommodate for low and no-light situations in your CCTV system. Today we’d like to address changes in light with video surveillance.

Light, as well as darkness, needs to be dealt with in specific ways. In this article, we’ll talk about two of those ways: the auto iris feature and wide dynamic range.

The main difference between the two is how they handle and account for changes in light that a security camera encounters.

The auto-iris feature, as you may have assumed, acts like your own eye’s iris. It adjusts to allow a certain amount of light to enter down to the imaging sensor. For instance, this is a very important feature to have on an outdoor security camera when it begins to become dark—this auto iris opens wider to allow in more light. The opposite is true for that same outdoor camera if it were a bright, sunny day.

With the wide dynamic feature, the area of concern becomes a single frame—it’s all about contrast within one area. Picture a loading dock. If a security camera is monitoring the loading dock door from the inside and it suddenly opens on a very sunny day, a camera without wide dynamic range will show a bleached spot where the door opening is and black areas around it without detail.

WDR balances out the bright spot and the dark areas. It makes it possible to see detail in these areas—it lightens up the dark and takes the bleach out of the bright spot.

So basically, auto iris is necessary for changes in light, not necessarily stark contrast within the same picture as is wide dynamic range.

And with many of the newer cameras nowadays, auto-iris is on the chip inside of them electronically already, so you don’t have to take any steps. Some have auto-iris lenses also. But just be sure to ask the question of your security integrator, because there are some dealers who may try to sell cameras of low quality without auto iris.

So when light (or lack thereof) is discussed when designing CCTV systems, commonly, infrared security cameras will be brought up. But don’t forget to talk about changes in light and contrast in light within a frame. The auto iris feature and wide dynamic range are important pieces in the video surveillance puzzle.

Thanks for spending some time with us today.


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