1. Video Quality
Lens
Once you have selected a camera, the next step is to select the appropriate lenses and any other relevant components necessary in the system. In this section, we are going to talk about lenses.

2. Introduction
This section will bring you through the following concepts about:
1. Basic knowledge for choosing a lens
2. How to adjust the lens
Introduction
This section will bring you through two main concepts of a lens:
Basic knowledge for choosing a lens
How to adjust the lens

3. Agenda ● Getting Started ● Basic Concepts ● Adjusting the Lens
--Scene Inspection
--Read the Lens Spec
● Basic Concepts
--Lens Size
--Mount Type
--IR Lens vs. Normal Lens
--Aperture
--Fixed / Manual Iris
--Auto Iris
--The Covered Area: Focal Length
--Fixed Lens
--Varifocal Lens
--Zoom Lens
--Depth of View
● Adjusting the Lens
--Tune Your Lens for the Best Video Quality
-- Determine the Depth of Field
Please briefly skim through the Agenda

4. Getting Started
Let’s get started!

5. Scene Inspection Lighting Target Distance Field of View Mount Type4
Lighting
Target 1
Mount Type
Camera Location 5
Scene Inspection
Before selecting the lens, you must define what specifications the lens should meet.
Start with a scene inspection and collect certain information.
1: Define the target you’d like the camera to watch: is it going to be a person’s face or the entire store?
2: Find the object distance from the camera
3: Define the area that you want to see through the camera, it’s called Field of View
4: Understand the possible lighting conditions, for example: is the lighting frequently changing?
Is the camera watching Day and Night?
5: Confirm the camera’s mount type and location
Distance 2
Field of View 3

6. Read the Lens Spec Read the Lens Spec
All this data is the key to the suitable lens specification.
Which are generally described in 7 parameters
The first one, size, refers to the size of the lens and needs to match up with the camera sensor’s size.
The second one, mount, refers to the lens mount and depends on the camera.
The third one, type, refers to whether or not a lens can capture IR light. An IR lens should used with a D/N camera.
The fourth, iris, refers to the mechanism for controlling the amount of light that enters a lens
The fifth, aperture, refers to the an opening through which light travels through a lens.
The sixth, focal length, is related to the suitable distance between the target object and the camera
We will later on bring you through the basic concepts about theses parameters.

7. Basic Concepts
Basic Concepts

8. Lens Size Lens size Image sensor size Size 1” 1/3” 1/2” 2/3” 1/4”
To select the correct lens size, you should first know the size of your camera’s image sensor.
CCTV camera generally use image sensor sizes ranging from to 1 inch in ¼ inch in diagonal length
Lenses are also designed to fit these image sensor sizes
You should always match the lens to the same size of image sensor
Suppose you have a camera that comes with a 1/3” image sensor, in front of which is a line-up of 6 people standing in a row
With a lens designed for bigger sensor size like 2/3”, it’s possible that even the lens’ viewing angle is able to see 6 people, the image sensor is not big enough to catch the red guy and blue guy.
With a ¼” lens, it’s possible that the image data can’t fulfill the whole image sensor, and thus causes black corners around the resulted image.
If the lens and image sensor are perfectly matched by size, all details the lens captures will be also be captured by the image sensor.
1/3” lens
1/3” image sensor

9. Compatible Camera Mount
Mount Type
Lens mount
in the camera
Sensor
12.5 mm mm
CS mount
C mount
Lens Type
Compatible Camera Mount
C mount lens
C mount camera
CS mount lens
C mount lens+ adapter ring
CS mount camera
C and CS mount are the two standard lens types for CCTV cameras.
The only difference between them is that CS mount lens needs only 12.5mm from its rear flange to the camera image sensor to focus
while C mount lens needs a distance of 17.25mm.
Most of modern CCTV cameras come with CS mount design.
CS mount lenses can only be used with cameras supporting CS mount.
C mount lenses can be used on cameras having C mount standard,
Also, with a 5mm C/CS ring adaptor, a C mount lens can perfectly fit into the camera’s CS mount like a CS lens does.
CS mount
Camera
C mount
Lens
C mount
Lens
5mm C/CS Adapter Ring

10. Make IR and visible light fall on the same plane
IR Lens vs. Normal Lens
Cameras can see IR light ; human eyes can’t
What is IR lens?
Visible
Infrared
Visible Light
Ultraviolet
Infrared
Visible
Light
Recognized
IR light
Visible light
Normal lens
Lens
Function
Applied Scene
Normal lens X
Day only
IR lens
Make IR and visible light fall on the same plane
Day and night
In most environments, there are three types of light: ultraviolet, visible, and infrared.
Among the three, both visible and infrared lights can be captured by the image sensor and influences the resulting image produced by the camera.
Since visible and infrared are different types of lights, often they land on different focal plane after travelling through the lens.
However, IR light is an important factor to enhance the image clarity during night scene.
When using IR illumination for night video, through a normal lens you can see the final picture is blurry due to being out-of-focus.
An IR (or IR corrected )lens is designed to let both light waves land on the CCD at the same focal plane, giving the viewer a focused picture.
So the normal lens is suitable for the scene where lighting condition is sufficient and stable so the camera can stay in color mode and have IR cut-filter in front of the image sensor to cut out any IR light waves to avoid IR-related out-of-focus. Examples of such condition are for indoor with abundant constant lighting or outdoor in day time.
The IR lens is important when IR illuminators are used in conjunction with the camera, especially the D&N cameras where IR cut-filters are automatically removed from the image sensor to allow IR light waves to reach the image sensor.
IR lens

11. Iris
Aperture
Pupil in human eyes= Aperture in the lens , the hole that opens to let the light in, controlled by iris, measured as the F number. EX: F1.6
F8.0
F4.0
iris
Bigger F-number
Smaller iris opening
Less light coming in
Illumination
Reflection
Before learning about the iris and F-number, it’s important to know what they are for.
Enough light is an essential element for making a clear image.
The aperture, a hole inside the lens, serves as the lens’ version of a human pupil that opens to let the light in.
The lens uses the iris to determine how much light are let into the aperture, which is measured by F number.
The larger the F number is, the smaller the aperture is and the less light passes through
The size of the iris opening is represented by the F-number.
As the picture shows, you may observe that with bigger F number, the iris opening is smaller, so less light is let through the aperture, which causes darker image produced. Vice versa.
So you only need to remember that, the bigger the F-number, the smaller the iris opening and the smaller the amount of light that passes through the lens.
Lens
Iris

12. Applied Lighting Environment
Fixed/Manual Iris
Types
Fixed iris
Manual iris
Size of aperture
Not adjustable
Adjustable
Applied Lighting Environment
Stable lighting condition
EX: Offices / restaurants / elevators
Benefit
●Cost-effective
●Easy to install
Suitable for wide range of scenes
Let’s move on to the iris used by lenses.
The fixed iris, as its name suggests, is fixed and does not allow aperture to be adjusted.
It is only suited for the indoor environment with constant light source such as fluorescent light.
Mostly applied in offices, restaurants or elevators. It is inexpensive but and works well under proper applications. Also, its installation is simple as it requires no iris adjustment.
The manual iris, allows us to control the iris manually, through a dial in the lens mechanism labeled as “open-close” or “o-c”.
Like fixed iris, the manual iris control is also used in circumstances in which the light condition won’t vary. But it can cope with a wide range of scenes, thus helps to reduce effort on choosing among several fixed iris lenses.
Fixed iris
Manual iris control

13. Applied Lighting Environment
Auto Iris
Types
Video-drive
DC iris
P-iris
Control
Lens
ISP
Applied Lighting Environment
Changing light , outdoor (Day/Night)
EX: Entrance / Parking lot / Intersection
Benefits
Used widely on analog cameras
●Less expensive ●More precise than video-drive lens
●Most precise
●Suitable for high-megapixel or HD cameras
Auto Iris
The automatic iris lens controls its iris automatically. This type of iris control is useful in environments where the light condition changes frequently. Such as outdoor applications or any indoor application where the lighting condition varies with outdoor lighting. The iris is controlled by either the lens or the camera and changes according to the light conditions so that the amount of light captured is always ideal.
There are 3 kinds of auto iris lenses, video-drive / DC-drive and P-iris
You should check which type your camera supports.
Video-drive lenses adjust the iris size based on the brightness of the image in the video signal, the calculation is done by an electronic unit in the lens. They are generally used on analog cameras.
DC-Drive lenses use a control signal from the camera image signal processor to adjust the iris size, which is faster and more precise.
P iris stands for “precise” iris. It uses very sophisticated electronics and microscopic stepping motors that can handle extremely lighting conditions where DC iris control is too coarse; the size of the iris can be controlled very precisely to allow for properly image exposure while maintaining a good depth of field (which means objects both far and near are focused).
Video-drive iris
DC iris
P iris

14. The Covered Area: Focal Length
Vertical viewing angel
Horizontal viewing angel
Diagonal viewing angel
Focal length
Image sensor
Lens
Focal length:
Measured in mm, the distance from the optical center to the focal point. EX: f3.6mm
Focal Length
The viewing angle and the focal length of a lens are 2 key factors that should be considered when choosing the right lens that covers your desired target scene.
Focal length means, the distance from the optical center ( on the lens ) to the focal point ( on the image sensor) when the target object are in focus.
This directly affects the viewing angle of your target scene.
The smaller the focal length number => The wider the field of view. => The bigger area you can see with objects in the scene appear smaller.
Focal Length
Viewing Angle
Field of View
Object Size
Shorter
Wider
Bigger
Smaller
Longer
Narrower

15. wider scene, smaller objects
34.4°
8mm Lens
3.7°
80 mm Lens
35 m
Shorter focal length
Bigger viewing angle
wider scene, smaller objects
Take a look at the picture shown, a lens with 8mm~80mm focal length is used to focus on a yellow truck about 35 meters away.
You can observe that with the 80 mm focal length, the horizontal angle is narrower, and only a portion of the truck occupies the entire image.
With a shorter focal length, like 8 mm, the angle is much wider, and allows the whole truck and even the entire gate to be in view, though appearing much smaller.
Let’ review the simple fact again:
The bigger the viewing angle is,
the wider scene is covered,
the more objects are seen,
the shorter the focal length must be.

16. Fixed Focal Lens Fixed focal Focal length Not adjustable
Features
Fixed focal length
Generally around 3.0mm
Focus Adjustment
Manual or fixed
Application
For near objects, wide viewing angle covering around 90⁰
EX: Offices, warehouses
The choice of lens type is essential to your scene.
They come in 3 types: fixed focal, vari-focal and zoom
A fixed focal lens, or simply “fixed lens” has a fixed focal length with the focus adjustable via a ring or lever.
It is significantly less expensive than vari-focal lens and zoom lens and is used for applications where focal length does not need to be adjusted.

17. Vari-focal Lens Vari-focal Focal length Manually adjustable
Features
Changeable focal length within a range
Focus Adjustment
Manual
Application
More flexible for different scene demands.
EX: Gates, retail shops
This is a design of lens that has allows manual adjustment of focal length over a certain range.
This type of lens is the better choice if you’re unsure of the ideal object size in the resulted image, the ideal viewing angle, or if can’t find a suitable fixed lens.
It’s also flexible for a scene where the installation points might change at later times.

18. Zoom Lens Zoom Focal length Not changeable
Features
●Variable focal lengths within a range, adjusted by zooming via remote control
●Zoom capability shown as ratio, EX:10X, or 280mm/28mm
Focus Adjustment
Auto
Application
For large area, long distance watching
EX: casino, traffic, central squares.
Like vari-focal lenses, zoom lenses have variable Focal length too. However, the focal length adjustment on a zoom lens is motorized and can be done locally or remotely by controlling the zoom level.
Such lenses also refocuses automatically as zoom level changes.
The zoom capability is usually represented in the spec as zoom ratio like 10X, 18X, 35X, etc. and defined by the maximum and minimum focal length For Example: an 18X optical zoom lens with mm focal length. If you divide 84.6 by 4.7, you get 18 and hence “18X.”
The most common need for a zoom lens is for applications where large areas are normally covered but when necessary, close-up shots at certain objects can be accomplished to show details.
Such lenses are mostly applied by speed dome or PTZ cameras for applications like traffic, casinos or central squares.

19. Depth of Field Depth of Field:
The distance between the closest and furthest points that are in focus under the same focus adjustment.
Depth of Field or DoF
In order to understand how to set a proper scene composition, it is very important to understand the concept of depth of field.
When focusing a lens on an object, there is a certain distance range in front of and behind the focused object that also comes into focus. This range is called “depth of field” and indicates the distance between the closest and furthest points that come into focus under the same focus adjustment. In other words, the depth of field means the area of sharpness.
When the distance between the closest and farthest points that come into focus is long, the depth of field is called “deep” and when short, the depth of field is called “shallow”. In the example we can see the same scene with different depth of fields, the one to the right has a deep depth of field because the three cars are all in focus. The one to the left has a shallow depth of field because the only car in focus is the red one in the very front and the other two cars outside the depth of field appear blurry.
A longer focal length, larger aperture or shorter object distance will make a shallower Depth of Field and Vise versa.
Shallow depth of field
Deep depth of field

20. Adjusting the Lens
Adjusting the lens

21. Tune Your Lens for the Best Video Quality
Steps of tuning the lens:
Viewing Angle
Focus
iris
W T
∞ N
O C
Define the size
of the scene
Adjust the focus so that the viewing area is in focus.  
Adjust how much light allowed through the lens for the scene.
As your lens has been chosen, let’s start tuning it to fit the scene you want to shoot.
You should always keep in mind the order of steps for tuning the lens. Let’s take a vari-focal lens as our example.
1st, Define the viewing angle by adjusting the zoom ring.
Simply turn the ring toward “Tele” position to get a more close-up view or “Wide” position to get wider viewing angle.
After the angle is defined, tune the focus ring to your target object into focus.
Finally, based on the lighting condition of your scene, adjust the iris.
To increase Depth of Field, you can try turning the ring from O to C where you will observer a darker image but with more items in various distances come into better focus.
For the best result, you should try the adjustment in both Day & Night scenarios if it’s a D&N application where the camera has to work under very different light conditions.

22. Determine the Field of Depth
Depth of Field is governed by:
1. Object distance
2. Focal length
3. Aperture
DoF vs. Object distance
DoF vs. Focal length
DoF vs. Aperture
Let’s take a closer look at how to fine tune the Depth of Field.
You should consider the following factors that dictates the DoF:
The object’s distance to the lens.
Focal length of the lens
Aperture of the lens
Let’s first see how the object distance influences DoF.
DoF increases as the camera to object distance increases.
This means that, while keeping Focal Length and Aperture unchanged, shortening the distance between the camera and the target will decrease the DOF
As for the focal length, DoF decreases as focal length increases
This means that changing the focal length of a lens or zooming will also affect the DOF of an image.
Depth of Field increases as aperture size decreases, which means smaller F-number
To increase the DoF, you could turn the iris ring from O slowly to C
With focal length and object distance remaining constant, we can see that shrinking the aperture increases the DOF of the image.

23. Thank you