Training: Using Lens Calculators

By: John Honovich, Published on Sep 27, 2010

In video surveillance applications, lenses generally take a 'back-seat' to their sexier camera counterparts. However, selecting a proper lens for an application helps ensure the highest quality image. Specify a lens too narrow for your application and one will miss out on capturing the entire area of interest. By contrast, a lens that is too wide will result in poor video quality of the subjects monitored.

A lens calculator can determine the appropriate lens focal length required for a desired field of view and therefore optimize system performance.

Key Concepts

Before using any lens calculator tool it is important to understand a few key concepts:

  • Sensor Size or Format - Cameras have an imaging sensor that comes in a variety of sizes, such as, 1/4", 1/3", 1/2.5", and 1/2".  Calculator tools usually provide a means to select one of these values for the calculation. This sensor size or format is easily determined by looking at the specifications sheet of the camera being considered. Note that whether the sensor is a CCD or CMOS has essentially no bearing on calculations.
  • Focal Length (mm) - Lenses generally fall into two categories: fixed focal length and vari-focal length lens types.  The focal length is essentially the distance between the lens and the imaging sensor. This distance determines how wide or narrow the scene captured will be. Shorter focal lengths are able to capture relatively wider scenes, while longer focal lengths provide tighter viewing angles for capturing more distant objects.  Vari-focal lenses have the advantage of providing a range of focal-lengths for added flexibility and control.
  • Horizontal Field of View (FoV) - The horizontal field of view (HFoV) is probably the most practical and well recognized property of the camera/lens system. It represents the width in units of length (feet or meters) of the camera scene at a specified distance from the lens.  This is a measurement typically obtained first-hand, perhaps during a site survey. It can also be theoretically calculated given a 'distance from lens' parameter and a 'lens angle' parameter.

IPVM Calculator

IPVM has the industry's best camera / lens calculator. Try it out here.

Learn how to use it below:

In this video, we guide you through the basic usage of a representative free online calculator tool. We take a quick tour of the lens calculator interface and highlight some key usage points. Then, we walk-through a few basic examples to better illustrate usage of the calculator tool. You'll see a unique feature of the tool that dynamically updates a reference image based on the input from the user.  This gives the user a visual sense of the camera/lens system being considered.

 FoV Concepts

Get Notified of Video Surveillance Breaking News
Get Notified of Video Surveillance Breaking News

In this video, we provide a conceptual explanation on how field of views (FoVs) are derived. You'll learn that FoVs are dependent on properties of the camera (sensor size), properties of the lens (focal length) and the distance from the lens being considered.  We use a diagram to clearly illustrate why a larger sensor size results in a wider FoV for any given lens focal length.

Pixels/Foot Concepts and Application

In this video, we demonstrate some examples of how a lens calculator tool might be used in a more thoughtful video surveillance design scenario. We'll revisit the earlier examples provided in the 'Basics' video and delve deeper into the tool's ability to predict image resolution or pixels/foot for a given CCD/CMOS resolution and horizontal FoV. 

2 reports cite this report:

New Surveillance Products Spring 2011 Final on Apr 06, 2011
In this report, we provide a single source listing new video surveillance products announced in Spring 2011 and in conjunction with ISC West.For...
Gish vsCalc iPhone/iPad App Reviewed on Mar 16, 2011
In this note, we examine a new iPhone/iPad application from Gish Technologies for calculating video surveillance. The goal of the application is to...
Comments : Members only. Login. or Join.

Related Reports

Last Chance - Camera Course Winter 2020 on Jan 30, 2020
This is the only independent surveillance camera course, based on in-depth product and technology testing. Lots of manufacturer training exists...
IPVM Camera Calculator User Manual / Guide on Oct 16, 2019
Learn how to use the IPVM Camera Calculator (updated for Version 3.1). The guide below includes instructions, images, gifs, and videos...
Camera Focusing Tutorial on Oct 14, 2019
Camera focus is fundamental to quality imaging. Mistakes can significantly reduce details, making cameras less effective. In this guide, we...
PlateSmart LPR Profile on Jan 31, 2019
PlateSmart Technologies claims to "turn any conventional surveillance camera into a license plate recognition camera" We spoke with PlateSmart to...
Startup Spectral Edge RGB+IR Claims "Unique Low Light Performance Tech" on Apr 03, 2019
This UK startup, born out of university research, is boldly proclaiming that they deliver "Unique low light performance tech for video surveillance...
Lens Focal Length Tutorial on Jul 10, 2019
3mm, 6mm, 2.8 - 9mm, 5 - 50mm, etc. Camera specifications often list lens lengths but what do they mean? These metrics are important in...
Lens Iris Tutorial on Aug 08, 2019
Cameras, like humans, have irises, controlling the light which hits the imager and impacting image details. However, cameras have multiple types of...
Camera Field of View (FoV) Guide on Nov 13, 2019
Field of View (FoV) and Angle of View (AoV), are deceptively complex. At their most basic, they simply describe what the camera can "see" and seem...
Camera Calculator V3.1 Release Improves User Experience on Oct 17, 2019
IPVM has released a new version of our Camera Calculator, V3.1, with significant user experience improvements, a new development plan, and an...
Biggest Low Light Problems 2019 on Nov 08, 2019
Over 150 integrators responded to our survey question: "What are the biggest problems you face getting good low-light images?" Inside, we share...

Most Recent Industry Reports

Video Surveillance 101 Course - Last Chance on Feb 20, 2020
This is the last chance to join IPVM's first Video Surveillance 101 course, designed to help those new to the industry to quickly understand the...
Cheap Camera Problems at Night on Feb 19, 2020
Cheap cameras generally have problems at night, despite the common perception that integrated IR makes cameras mostly the same, according to new...
Milestone Launches Multiple Cloud Solutions on Feb 18, 2020
Milestone is going to the cloud, becoming one of the last prominent VMSes to do so. Milestone is clearly late but how competitive do these new...
Video Surveillance Architecture 101 on Feb 18, 2020
Video surveillance can be designed and deployed in a number of ways. This 101 examines the most common options and architectures used in...
UK Stands Behind Hikvision But Controversy Continues on Feb 18, 2020
Hikvision is exhibiting at a UK government conference for law enforcement, provoking controversy from the press, politicians, and activists due to...
IronYun AI Analytics Tested on Feb 17, 2020
Taiwan startup IronYun has raised tens of millions for its "mission to be the leading Artificial Intelligence, big data video software as a service...
Access Control ADA and Disability Laws Tutorial on Feb 17, 2020
Safe access control is paramount, especially for those with disabilities. Most countries have codes to mandate safe building access for those...
ISC West 2020 Removes China Pavilion, No Plans To Cancel Or Postpone on Feb 17, 2020
ISC West plans to go on next month, amidst concerns over coronavirus. However, the Asia / China Pavilion has been removed, show organizers...
Hanwha Wisenet X Plus PTRZ Tested on Feb 14, 2020
Hanwha has released their PTRZ camera, the Wisenet X Plus XNV-6081Z, claiming the "modular design allows for easy installation". We bought and...
PRC Warns Against China Video Surveillance Hacks, Hikvision Targeted on Feb 14, 2020
Hackers are targeting China video surveillance manufacturers and systems, according to the PRC's main cyber threat monitoring body. The hackers...