Lens Selection Recommendations

Author: John Honovich, Published on Jan 30, 2013

Selecting the right lens can be confusing and tough, especially because lenses are often integrated into cameras, severely restricting flexibility to mix and match the right lens feature sets. In this tutorial, we examine 7 key criteria in selecting the appropriate lens. They are:

  • Lens Length / FoV Width
  • Varifocal or Fixed Focal
  • F-Stop
  • Iris Type
  • Shutter Speed
  • Color vs D/N Lenses
  • Lens 'Resolution'

Lens Length / FoV Width

You need to know what lens length you need, because this determines how wide (or narrow) a Field of View (FoV) you can see. Do you want a 3mm, 8mm, 12mm, 50mm lens? The longer the lens, the narrower the FoV. See our lens length and FoV tutorials for details.

Typically in surveillance, 10mm or less is used because wide FoVs are most common. But there are many applications where one needs to see far away, requiring longer lenses. To determine exactly the lens length needed, use a lens calculator. For an example of what you need to see miles away, see this super long lens discussion.

Varifocal or Fixed Focal

Lens length is either fixed or adjustable. For instance, the lens may be 3mm with no other options (that's fixed) or adjustable between 3mm - 10mm (that's varifocal). Overwhelmingly, surveillance users prefer varifocal (see our survey results on varifocal vs fixed for more). However, fixed focal lenses are less expensive and typically found on lower cost cameras, so are often used to reduce costs.

If you use varifocal, you have more flexibility adjusting the FoV. If you used fixed, the only choice to do the same is move the camera closer or farther away from the subject.

F-Stop

F-Stop is a strong indicator and determiner of low light performance. The higher the F number, the less light the lens will pass and the more likely the camera will have problems in low light. For instance, an f/1.4 lens takes in a lot more light than a f/2.8 one (actually 4x). See our F-stop tutorial.

Always check the lens F-stop, especially if comparing different form factors or wide price ranges, as the differences can be extreme and have a huge practical impact

Get Video Surveillance News In Your Inbox
Get Video Surveillance News In Your Inbox

Iris Control Type

The iris is the opening that allows light to pass through the lens and to the camera. The four common choices are fixed, manual, auto and P iris. While higher end cameras typically use auto or P iris, our testing does not show much benefits for iris choice. For more on the differences between these controls, see our Iris tutorial.

Shutter Speed

The shutter is NOT part of the lens but is related because it significantly impacts the sensor's exposure to light. Many cameras use both iris and shutter speed control to regulate light input (see our shutter speed vs iris tutorial).

The shutter determines how long the sensor is exposed to light and is typically expressed in fractions of a second (1/1000s, 1/100s, 1/30s, 1/3s, etc.). See our shutter speed tutorial for more.

One big issue to beware is slow shutter speeds. Many manufacturers market this as a miracle technologically because, in really dark scenes, it can make an image bright but it creates blurring and ghosting of moving objects. This is why we say, this feature called Sens Up, is for suckers.

Lens 'Resolution'

While cameras are typically marketed by their resolution, i.e. pixel count, like 1MP, 2MP, 3MP, etc., lenses are not. First, pixel count has no direct meaning because there are no pixels in lenses. Pixels are a part of image sensors, not lenses.

However, to make it simpler for users, lens manufacturers sometimes rate their lenses for resolution, such as 1.3MP or full HD, etc. Technically, the more accurate term is line pairs / millimeter (lp/mm) or how many lines a lens can display in a given area, with the more the better. The problem is that lens manufacturer rarely reveal this metric, making it useless as a judging criteria.

The best bet is to use the lens that the camera manufacturer recommends. As long as your manufacturer is reputable, they will recommend or require you to use a certain tested and verified lens. Using a cheap lens will not save much money but can cause problems. The exception to this rule of thumb is if you have done your own comparative tests with the alternatives you have considered. For instance, see our HD lens shootout.

Megapixel and Super Megapixel

Two rules of thumbs here:

  • Never use an SD lens on a megapixel camera. You will almost certainly significantly degrade image quality.
  • For 3MP or less resolution, many quality lenses exist. Just make sure they are rated for MP and the camera manufacturer approves. Above 3MP, it is much more difficult. First, varifocal lenses are much rarer. Secondly, the lenses tend to be significantly more expensive.

Color vs Day/Night

If you are using a day/night camera with a mechanical cut filter, use an IR corrected (sometimes marketed Day/Night) lens. Otherwise, you may have a focus / blurriness issue at night. The good news is IR corrected lenses are common and do not cost much more.

Focusing

Even if you have the right lens, you still need to make sure it is in focus. This is especially important since most use varifocal lenses that require fine focusing after adjusting for the right lens length for one's scene. Auto back focusing / auto focusing are increasingly common and help greatly with this. IP camera installation tools should be considered but it's tricky finding the right one as there's no great, general solution (as there was with analog cameras). For more, see our focusing tutorial.

1 report cite this report:

Resolution Tutorial on Dec 28, 2017
Understanding video surveillance resolution can be surprisingly difficult and complex. While the word 'resolution' seems self-explanatory, its use...
Comments (1): PRO Members only. Login. or Join.

Related Reports

Multicasting Surveillance Tutorial on Jan 04, 2018
Network bandwidth can be a concern for some surveillance systems. While improvements in video codecs, such as smart codecs for H.264 and H.265,...
Cabling Best Practices Guide on Jan 03, 2018
Surveillance cabling can be a major problem. Poorly installed and maintained networks are often costly, lengthy, frustrating ordeals to...
QoS for Video Surveillance on Dec 29, 2017
Along with VLANs, QoS is one of the most misunderstood topics in IP surveillance networks. Many purported "experts" claim it is required in any...
Repositionable Multi-Imager Camera Guide on Dec 22, 2017
Multi-imager usage has been growing strongly over the past few years. Now, a new segment of multi-imagers has taken off, with many manufacturers...
STP vs UTP for Video Surveillance Tutorial on Dec 20, 2017
For many video system designers, deciding which ethernet cabling to use is a quick decision: go with the cheapest.  However, this overlooks the...
Lock Status Monitoring Tutorial on Dec 18, 2017
Just because your doors look secure does not mean they are. Unless access systems are using lock status monitoring, the doors and areas they...
Access Controller Software Guide on Dec 11, 2017
Properly configuring access controllers software is key to a professional access system. These devices have fundamental settings that must be...
2018 Video Surveillance Cameras Overview on Dec 11, 2017
This report concisely explains the developments for surveillance cameras offered in 2017 and the state of offerings going into 2018, including...
Hazardous & Explosion Proof Access Control Tutorial on Nov 27, 2017
Controlling access to hazardous environments require equipment meeting specific ratings that certify they will not start fires. Understanding those...
Deep Learning Tutorial For Video Surveillance on Oct 17, 2017
Deep learning is a growing buzzword within physical security and video surveillance. But what is 'deep learning'? In this tutorial, we explain...

Most Recent Industry Reports

'Defiant' Hikvision 'Strikes Back' At WSJ And US on Jan 16, 2018
The fight is on. Hikvision and their owner, the Chinese government, 'strikes back' against the Wall Street Journal and US politicians raising...
Winter 2018 Camera Course Registration on Jan 16, 2018
Learn video surveillance and get certified. Save $50 on the course, ending this Thursday the 18th, plus get access to 2 class times - 'day' and...
The 2018 Surveillance Industry Guide on Jan 16, 2018
The 300 page, 2018 Video Surveillance Industry Guide, covering the key events and the future of the video surveillance market, is now available,...
Edward Snowden Haven App Tested on Jan 16, 2018
Global coverage followed the December 2017 announcement that Edward Snowden was leading a team developing Haven, an app "that leverages on-device...
This High Schooler Is Excited About His Future Security Career on Jan 15, 2018
A common lament is that smart, young people have little interest in surveillance systems. In fact, discussions like Should Talented Young People...
"First Of Its Kind" Stove Knob Alarm Sensor (2GIG) on Jan 15, 2018
At CES 2018, 2Gig/Nortek announced the Stove & Grill Guard, a "first of its kind" sensor in the security industry, allowing users to be...
Amazon Deep Learning Partnership With AgentVi on Jan 15, 2018
Amazon is aiming to grow its Kinesis Video Streams offering that "enables you to quickly build computer vision and ML applications" in the cloud....
Hikvision Removed From US Army Base, Congressional Hearing Called on Jan 12, 2018
Hikvision has been removed from a US Army Base and a US congressional committee is planning a hearing on cybersecurity risks and specifically,...
CES 2018 Show Final Report on Jan 12, 2018
This is IPVM's final edition of our 2018 CES show report. Below are already numerous images and commentary, with more coming tomorrow.   CES is...
Hanwha ExtraLux Camera Tested on Jan 11, 2018
Hanwha has released the latest in their Wisenet X line, the "extraLUX" series, claiming to "capture crystal clear, true-color images in low-light...

The world's leading video surveillance information source, IPVM provides the best reporting, testing and training for 10,000+ members globally. Dedicated to independent and objective information, we uniquely refuse any and all advertisements, sponsorship and consulting from manufacturers.

About | FAQ | Contact