The Complete Guide To Security Camera Resolution
You’re probably aware that the majority of IP security cameras range in resolutions from 1080p to 4k, with the latter considered higher quality.
But do you know what these numbers stand for and what the difference means? Further, are you able to identify which type is necessary for each application?
If not, don’t worry. Many so-called ‘security experts’ are not even aware of the objectively proper way of determining the correct resolution needed.
In this guide, we will show you how to understand camera resolution, including what 1080p and 4k stand for. We’ll then move on to explain the concept of Pixels-Per-Foot, the correct way to determine what resolution you need for a given application. Understanding this concept will provide you with a considerable advantage when working with or choosing a security solution.
What Is A Pixel?
Any digital image or video displayed on a screen is made up of many smaller units called pixels. How many pixels an image or video has is directly related to how clearly it will display.
The higher the number of total pixels on your screen, the smaller each pixel will be. The result is that the pixels become so little we can no longer detect them, and thus the image becomes clear. For security camera purposes, this means greater detailed evidence.
A lower quality image, on the other hand, looks ‘pixelated’ when the pixels are large enough to be detected. Obviously, in this case, there are fewer total pixels that can fit on the screen, so these lower quality images have lower pixel counts.
How Many Pixels In An Image?
Security cameras generally give a rectangular image of a scene. Knowing this, we can safely assume that the total area (number of pixels) can be represented by multiplying the height (or vertical range) by the length (or horizontal range) of the image.
1080p resolution means that the camera’s image will have 1920 horizontal pixels and 1080 vertical pixels, for a total of approximately two million pixels or more commonly stated 2 megapixels.
To add confusion, both 1080p and 4k are representative of the number of pixels along one of the ranges (horizontal or vertical) of the grid. However, they are not representative of the same range!
The 1080 in 1080p represents the 1080 pixels on the vertical range, whereas 4k represents the (actually 3840) pixels across the horizontal range. It will be easier to illustrate this by showing you the actual full dimensions.
A 1080p Camera:
Will Display Footage With:
1920 Horizontal Pixels x 1080 Vertical Pixels
= Approximately 2 Megapixels (2 Million Pixels) Total Area.
A 4k Camera:
Will Display Footage With:
3840 (Roughly 4k) Horizontal Pixels x 2160 Vertical Pixels
= Approximately 8 Megapixels (8 Million Pixels) Total Area.
For now, let’s just keep in mind that the camera name is representative of the number of pixels along either the horizontal or vertical axis of a rectangular image. In the case of 1080p, it is along the vertical side, whereas for 4k, it is along the horizontal side.
Since we said the total number of pixels corresponds to resolution quality, we can safely assume that a 4k camera (with 8 million pixels) has roughly four times better resolution than a 1080p camera (with 2 million pixels) would.
Why Not Just Use 4k Everywhere?
This is certainly an option; however, depending on the applications, it can be more costly than necessary. Perhaps more importantly, in addition to the added camera cost it will drastically increase storage requirements and costs.
An increase from 1080p to 4k requires almost four times the amount of storage. If this is overlooked, the amount of recorded footage in your server can quickly spiral out of control. When adding storage be sure to consider using surveillance grade hard drives for a reliable long-lasting system.
Within a single facility or property, there are many types of areas that need to be recorded, each requiring different resolutions depending on the nature of the scene and desired intent for capturing images in that area.
For example, a 1080p camera is more than sufficient for most interior hallways, and will only take up one-quarter of the valuable storage space that a 4k recording would. For a large open area, however, a 4k can capture up to 4 times clearer images which may be the difference between unusable and useful camera evidence.
So How Do I Know Which Resolution I Need Which Area?
Here is where even the experts struggle, and we often see mistakes. Some security companies make recommendations based on what they feel is best; others say you need “the best” without understanding your objectives for the proposed system. The truth is that these methods are guesses at best.
Luckily there is an objectively correct way to determine what resolution camera you need for a given scene. It is a calculation known as Pixels-Per-Foot (PPF).
In Pixels-Per-Foot, we determine how many horizontal pixels are required to identify, observe, or detect a specific object.
Trying to identify a stranger may require 120 pixels per ft, whereas detecting a vehicle entering a parking lot could be as low as 20 pixels per ft.
As a general rule of thumb, we can say:
Identify: At least 120 pixels-per-foot.
Observe: At least 60 pixels-per-foot.
Detect: At least 20 pixels-per-foot.
Which of the three are required will vary based on the objective of that specific proposed camera.
To find the PPF, we must divide the horizontal number of pixels in a frame by the number of physical feet wide that the scene you are filming is. In other words, if you need a camera to capture an area that is 25 feet wide, you will divide the horizontal pixel number by 25.
PPF = (Horizontal Pixels) / (Width In Feet Covered By Camera)
Finding Horizontal Pixels
First, we must see how many horizontal pixels a camera’s display will have.
Recall from earlier that:
A 1080p Camera Has: 1920 Horizontal Pixels x 1080 Vertical Pixels
A 4k Camera has: 3840 Horizontal Pixels x 2160 Vertical Pixels
For the sake of PPF, we can safely ignore vertical pixels and only focus on the number of horizontal pixels.
4k Cameras = 3840 Horizontal Pixels
1080p Cameras = 1920 Horizontal Pixels
Feet Covered By A Camera
For the Width In Feet Covered by the camera, we mean the actual physical area the camera will record. So if the camera captures a parking lot entrance that is 25 feet wide, the feet covered is 25.
For the example of an entrance that is 25 feet wide, we would do the following calculation for each camera type:
1920 (Horizontal Pixels) / 25 (Feet)
= 76.8 PPF
3840 (Horizontal Pixels) / 25 (Feet)
= 153.6 PPF
In This Case:
A 1080p Camera is sufficient for:
- Detecting (>20 PPF) &
- Observing (>60 PPF)
However a 4k Camera will be required if you need to:
- Identify a person’s face (>120 PPF).
Designing Your Camera Layout With PPF
Now that you have an understanding of how many Pixels-Per-Feet are needed depending on the area size and camera’s purpose, you can layout cameras around the property to meet your security needs.
In most security applications, it makes sense to identify pinch points (areas that allow entry & exit, like a doorway or parking lot entrance). It’s recommended to have a high PPF (>120) camera set up to monitor these pinch points. This allows you to Identify someone as they enter or exit through the relatively narrow area.
Once a person has entered through the pinch point and been identified, we can then observe them as they move around larger areas not possible to cover in fine detail.
Additional Camera Features
Resolution is not the only factor that helps you provide clear evidence. For each application, it is essential to consider the following features to ensure high-quality and usable evidence.
Night Time Vision:
Always ask for a sample image or demonstration of the camera in nighttime lighting conditions.
- Does the camera provide details and stay in colour at low light levels?
- When it goes to Infrared black and white mode is the image still clear?
Wide Dynamic Range (WDR):
This is important in areas with harsh lighting conditions. For example, an exterior doorway that allows the sun to contrast with a dark interior.
- Cameras without true WDR will struggle to capture details during mixed lighting conditions.
Temperature & Weather Ratings:
Toronto’s unique climate ranges from ice-cold winters to hot and humid summers.
- Cameras installed outdoors must have the proper temperature and weather ratings to ensure performance in either extreme.
Depending on where the camera is installed, it is often important to include vandal ratings to help the camera stand up to abuse.
- Damage can be caused by both intentional vandalism, and accidental such as a warehouse forklift running into a camera. Vandal rated cameras can help your cameras survive in these harsh conditions.
- Always follow the more objective Pixel-Per-Foot approach, rather than using a guessing method.
- Ensure you are factoring the additional storage required when using higher resolution cameras.
- 1080p cameras are more than sufficient for most interior hallways and small to medium size rooms.
- 4k cameras can provide great detailed coverage of large open areas interior and outside.
- Review additional camera features besides just resolution, as they have as big of an impact on providing quality video evidence.
There are many factors at play when it comes to camera resolution and quality evidence. We hope that this guide will make this territory a little bit easier for you to navigate.
If you’re unsure or require assistance, we are more than happy to guide you through the process one on one. Depending on the factors listed in this guide, we can recommend the right resolution cameras for your project. To get started with Square Security schedule a consultation here or call 416-460-7218.