Product specification & Software for IP Camera

IP Camera manufacturers provide product specification sheets that help you select the right camera for your IP security and surveillance system. But, which specifications are important?  They include such things as resolution, minimum light sensitivity, lens, WDR, signal to noise, etc.  This article reviews the important camera specs, and how to avoid being fooled by specsmanship (from the marketing department).

The importance of each of the camera specifications depends on your objective and application for your IP camera system.  For example, if you want to use the camera outdoors where it can get dark, then the low light specification is important. If you are only using the IP camera indoors, you may be more interested in the how wide a viewing angle you can achieve.  Here is a review of the important specifications.This is an important specification.  In the old days it was measured in TV lines, and they used a TV test pattern to analyze the resolution.  Today resolution is usually defined by the total number of pixels in the sensor or the horizontal and vertical pixels.  Marketing people also use the term “HD” and “720p” or “1080p”, and most recently “4K”.  It can be very confusing.  Here’s what each of the terms mean:

Megapixel Camera:  This is a general term used for any camera that has over 1 million pixels in the sensor. There are many cameras that have over 1 megapixel resolution.  For example, there are 2.0, 3.0, 5, 8, 10 and higher megapixel cameras. The pixels are organized in a matrix of horizontal and vertical pixels.  The relationship between the horizontal and vertical pixels is called the aspect ratio.   The aspect ratio (vertical to horizontal ratio) is usually 4:3 or 9:16 (wide).  For example a 1.2 Megapixel sensor on the Sony SNC-EM600 camera has 1280 horizontal pixels and 1024 vertical pixels.  The aspect ratio is 1280/1024 which is 1.24 or close to the 4/3 ratio (1.3).  The 2 megapixel Samsung SND-6084

 dome camera has 1920 x 1080 pixels, and the aspect ratio is closer to 16:9.  The latest sensors (especially the ones that claim 4K resolution) have different aspect ratios that are similar to the very wide formats used in the cinema market.

HD Camera:  This is more of a marketing term and is defined as either a 720p or 1080p type HD camera.  This specification comes from the video broadcast market rather than the security market and can be totally confusing.  Back in the old days, TV had only 525 horizontal scan lines per frame.  This is not the actual resolution, but rather physical scans of an electron beam on a CRT (Cathode Ray Tube). The total number of horizontal lines in a frame was made up of two fields (262.5 lines per field). The fields were interlaced, so we wouldn’t see the flicker.

Today 720p refers to 720 horizontal lines. The “p” indicates that the lines are progressive rather than interlaced.  There is only one scan per frame that includes 720 lines rather than 525 lines. The 1080p HD camera has at least 1080 horizontal lines.

720p cameras usually have a sensor with at least 1.0 megapixels. Pixel resolution is 1280 x 1024 (like the Sony SNC-EM600 1.3 megapixel camera), or it can be 1280 x 800 (like the Axis M3004 1.0 megapixel camera).

1080p cameras have at least a 2 megapixel sensor, and it is considered to be the higher resolution “HD camera”.  To confuse us, some manufacturers call their 3 megapixel or 5 megapixel camera “1080P” as well.

4K Camera:  This usually refers to a camera with over 8 Megapixels of resolution.  It has approximately 4,000 horizontal pixels. There is some difference between the definitions from the television industry and the security market.  The number of vertical and horizontal pixels and the aspect ratio are defined differently. For example Sony announced that their new (coming soon) camera has a chip with 4096 H × 2160 V pixels which runs at up to 60 fps and conforms to the Digital Cinema Initiative. Axis announced a camera with 3840 x 2160 which runs at up to 30 fps (which is called Ultra HD).  The marketing people call all these cameras “4K”.

Other Things that Affect Resolution:

The resolution of a camera is defined not only by the sensor, but also the lens and the electronic circuits. We sometimes see megapixel IP cameras selling for under $200.  Be careful.  You do get what you pay for.  The sensor may have the megapixels, but the lens may be plastic, and the result is a very low quality image. For more about IP Camera Resolution take a look at our blog article.

Minimum Illumination (or Low Light Sensitivity)

The minimum illumination is the lowest light level that provides a reasonable image from the IP camera. It is measured in lux.  This can be very subjective.  It depends on what you think is an acceptable image.  The low light level image you see is not only dark, but can also be very noisy.

At the low light level the amplifiers are working very hard and there can be circuit noise that affects the video image.  This is called the signal to noise (S/N) ratio.  The better manufacturers also include the relative level of the signal (IRE), which is a measure of how hard the amplifier has to work.  For example a camera that is operating at 30 IRE is receiving 30 percent of the signal from the sensor circuits, while one operating at 50 IRE is receiving 50 % of the signal.  The lower the number, the harder the amplifier has to work to boost the signal so it can be seen.  The noise level can be as high as 20% of the signal so the resulting video can look very noisy when the signal level is very low.

The minimum light level is also affected by the shutter speed, which relates to the frame rate.  The longer the shutter is opened the more light can reach the sensor. The longer the shutter stays open, the lower the frame rate. There are some camera specs that indicate very low minimum illumination (0.0001 lux), but this is measured at a shutter speed of 0.5 sec.  This translates to a maximum frame rate of 2 fps.

The minimum illumination level is also determined by the lens.  The lower the f-number of the lens the more light it will let through.  For more details about this take a look at IP Camera Low Light Sensitivity blog article.

For a more practical guide to how IP cameras perform at low light, take a look at our “IP Camera Low Light Test” which compared a number of IP cameras at low light levels.

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