Factors That Affect A Camera's Image Quality

1080p cameras are dominating the security camera market, and rightly so. After all, who doesn't want a security camera with good vision? However, contrary to popular belief, a camera's resolution isn't the only deciding factor for a camera's image quality. There are other factors, and knowing what these factors are can help you pick out the best of the best security cameras.

Factors That Affect A Camera's Image Quality

1. Lens

Before being translated into an electronic image, light passes through the lens first. There are three things to look at when comparing security camera lenses: the focal length, aperture, and iris.

The focal length, measured in millimeters (mm), affects the camera's field of view and focus. The shorter the focal length is, the wider the camera's field of view. However, note that wide-view cameras are nearsighted. They focus well on objects close to them, but not so well on objects farther away. On the other hand, narrow-view cameras can focus on both objects close to them and far away from them.

The aperture affects a cameras depth of field or how the camera focuses on the nearest and farthest objects. The aperture is measured in f-stops (e.g. f1.4, f1.8, etc). Basically, a lower number means a wider aperture and a wider aperture means a shallower depth of field. In a camera with a shallow depth of field, objects near the camera appear sharp and crisp, while objects farther away appear blurry. As the depth of field becomes deeper, however, the camera tends to focus on background objects. If balanced out properly, a camera with just the right aperture can produce clear images of objects both near and far.

Finally, the iris controls how much light can pass through the aperture. Low-light cameras allow more light to pass through, so if you place them in well-lit areas, the image will be washed out. Fortunately, most security cameras today have auto-iris, which means they automatically adjust to changes in light conditions. If it's bright, the iris lets in less light. If it's dark, the iris allows more light to pass through.

In security cameras, there are three types of lenses often used. There are fixed lens cameras, varifocal lens cameras, and zoom lens cameras.

Fixed lens cameras have a fixed focal point. If you know where you'll use the camera (e.g. Indoor or outdoor? Hallways or entire room?), you can choose a suitable fixed lens camera for your desired location. For example, to monitor an entire room, you need a fixed lens camera with a short focal length. To monitor a narrow hallway, on the other hand, you need a camera with a longer focal length.

Varifocal lens cameras have adjustable focal length. You can use them to monitor both wide rooms and narrow hallways. The catch? You need to adjust the focus manually every time you adjust the focal length. Otherwise, the final image will be out of focus.

The best type of lens to use is the zoom lens. It's kind of like a varifocal lens, but instead of adjusting the focal point or field of view, it just zooms in or out. However, it has auto-focus. You don't need to tinker with the camera every time you adjust the lens. It will focus on its own.

2. Image Sensor

The image sensor is a hardware component that captures light and converts it into an electronic image. Therefore, the quality of the image sensor dictates the overall image quality.
There are two basic types of image sensors: CCD (charged coupled device) and CMOS (complementary metal-oxide-semiconductor).

CCD is an older technology but is often considered superior to CMOS. CCD typically performs better in low-light condition, has wide dynamic range, lower white noise, and higher definition. However, CCD is more expensive to construct, produces lower frame rate, and consumes more power; all reasons why camera manufacturers today prefer CMOS.

CMOS sensors are compact, which means they take up less space. They are also less expensive and they produce better color and higher frame rate. There are also CMOS sensors that can match or even transcend the image quality of CCD sensors.

When looking at security cameras, there are four popular image sensor formats: 2/3", 1/2", 1/3",and 1/4" image sensors. Each format is suitable for different types of use.

The 2/3" format is considered high-end because of its high sensitivity and impressive performance in low-light environments making it a good option for outdoor cameras. The 1/2" format is mid-range. It's okay in terms of sensitivity and it can also function well in low-light. Most manufacturers prefer this format (or the slightly better 1/2.3" format) because it hits just the right spot between affordable production cost and image quality. The 1/3" format is even less sensitive, but it produces higher framerate. Finally, the 1/4" format offers the lowest image quality.

3. WDR/HDR

WDR and HDR are two different things, but they serve the same purpose: they improve a camera's dynamic range. Consider this: You're recording through a camera pointed at your window. As the window is bright (backlight), the camera adjusts the lens to let in less light so you can see what's outside the window. However, because there is less light passing through the lens now, dark areas become even darker and almost impossible to see clearly.

WDR and HDR solve this dilemma. They balance out lighting. The end result is an image with a lighting condition that is "just right."

Cameras with WDR or HDR are better than those without, but what about cameras with WDR versus cameras with HDR?

WDR (a.k.a. True WDR or Optical WDR) captures two images. One is low-light optimized and the other is high-light optimized. It then uses software to combine the two images and create one image with wide dynamic range. HDR (a.k.a. Digital WDR) only takes one image, adjusts it twice (one for low-light, one for high-light), and combines the two output images. The result is a digitally manipulated image with wide dynamic range. Between the two (HDR and WDR), WDR is preferred.

4. Frame Rate

The frame rate defines the number of frames or images a camera captures per second. A camera with a frame rate below 15 frames per second is choppy and painful to watch. It's almost like watching a stop-motion video. The sweet spot for most cameras is between 25 to 30 fps. If you go above 30 fps, the image quality will, of course, improve. However, a high frame rate also means higher bandwidth use, which is why most manufacturers settle for less.

5. Video Compression

Videos captured by security cameras are compressed before being sent to you. Unfortunately, when videos are compressed, they sometimes lose image quality. There are two popular video compression formats used in security cameras: h.264 and MPEG 4. Between the two, h.264 is the better choice. There is less quality loss when using the format and it offers better delivery of HD videos.

6. Night Vision

Most cameras with night vision use Infrared LEDs. IR LEDs allow cameras to see in zero-light conditions. The catch is that most of the time, the image turns black and white when night vision is switched on. There are also cameras that go the extra mile and offer colored night vision. They also use IR LEDs but they still provide colored images. Finally, there are cameras that are only operable in low-light conditions. These cameras often adjust their lens to be able to see in low-light, but they are useless in zero-light conditions.

When choosing a camera, you should also consider the night vision range, which is how far a camera can see in the dark. For outdoor cameras, the recommended night vision range is no less than 60 feet. For indoor cameras, a 30 foot night vision range is standard.

Beyond The Image Quality

Shopping for a security camera can be overwhelming. There are a lot of other things to consider beyond the camera's image quality. Does it add value to your home's security? Does it pose any threat to your privacy? Are the security features reliable? How about video storage? What's the cost of using the camera? Is it smart enough?

If you're feeling overwhelmed, don't worry, we got your back. Our team has been reviewing security cameras for years, and we've written a lot of useful articles including hands-on reviews that can help you. Feel free to browse our archive and if you have any questions, drop a comment. We'll be sure to get back to you as quickly as possible.

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