The Importance of Megapixel Lenses

Author: John Honovich, Published on Feb 21, 2009

Selecting the right megapixel lens is as confusing as it is important. The wrong choice of lens can make an expensive megapixel camera no better than a cheap analog camera. Unfortunately, manufacturers generally do not provide sufficient information on their lenses and general educational information on lenses is scarce.

[UPDATE: October 2011: We have completed the first ever Megapixel lens shootout comparing performance of Computar, Evetar, Fujinon, Tamron and Tuss lenses.

Here are the key issues with megapixel lenses:
  • Many systems designers are not used to evaluating lens details because lens quality was generally not a significant issue with standard definition cameras.
  • Manufacturers now label their lenses "megapixel lenses" but generally do not disclose a quantitative measure of how 'megapixel' their lenses are
  • Line Pair per millimeter (LP/MM) is a widely accepted quantitative measurement of the resolving power of a lens; however it is rarely disclosed
  • Even with a given LP/MM, the performance of a megapixel camera still varies depending on the size of the camera's pixels
Background Information
In this report, I draw on a number of excellent papers. I recommend you read these papers:

Not A Traditional Concern

When you are recording video at CIF or lower (which most of the world's surveillance cameras probably do today), any stock lens is likely to be good enough. For many years, limitations in analog transmission technology and storage placed a natural constraint on the quality of lens needed.

While a designer might be concerned about the range of focus for a varifocal lens or whether or not a lens was day/night capable, the resolution of a lens was not normally a critical issue to consider.

With megapixel, you suddenly switch from a world where 320 horizontal pixels was the norm to where 2000 horizontal pixels (a 3MP camera) is not uncommon. A 200-700% increase makes lens quality suddenly much more important.

Manufacturer's Technical Information is Unhelpful

Publicly disclosed technical information on lenses generally lack a quantitative measure that designers can verify. For instance, when you buy a megapixel camera, you always know how many megapixels the camera is (1, 1.3, 2, 3, 5 MP, etc.). With lenses, there is rarely any equivalent resolution stated. Worse, many manufacturers have started to label their lenses with big 'Mp' logos. This may help in differentiating it from a standard definition lens but it does little to identify how 'megapixel' it is.

However, manufacturers certainly have this information internally. It is not simply an issue that it does not exist. 

Part of the problem is that a lack of technical disclosure can help manufacturers cut corners and make their products seem better than what they are. (I am not saying that all manufacturers are doing this but it must be at least a partial factor for some manufacturers).

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

LP/MM is a Widely Accepted Technical Measure

Line pairs per millimeter is the widely accepted quantitative measure for the resolution of a lens. Basically, this metric describes how tiny the distance betweens lines can be for a lens to transmit. See this article for a good visual demonstration of this.

From what I can tell, standard definition cameras need about 30 lp/mm where megapixel lenses need at least 60 lp/mm (or more depending on the amount of megapixels).

Another interesting and important issue is that the resolving power of a lens (the lp/mm) decreases towards the edge of the image. In other words, a lens may have 60 lp/mm in the center but only 30 lp/mm toward the edges.  Making this more confusing, the standard way of expressing lp/mm in the surveillance industry seems to be quoting the lp/mm in the center of the image. As such, someone may tell you a lens is has a lp/mm for 1.3MP but it may only be capable of that resolution in the center of the image. On the exterior, the lp/mm may only be sufficient for standard definition imaging.

Lens Performance Impacted by the Size of Pixels

To make matters more confusing, the size of pixels for various megapixel cameras differ and that size impacts the selection of lenses. LP/MM expresses resolution for a given physical width (millimeters). However, the physical width of pixels in megapixel cameras varies because of different image size formats (1/3",1/2",2/3" etc.) and the number of pixels that need to fit on the imager (1.3, 2, 3, 5 MP etc.).

The practical importance is that the lp/mm metric is only relative to the size of the pixels on the camera. For example, a lens with 120 lp/mm might be great for a 1.3MP camera using a  1/2" imager but very poor for a 2MP camera using a 1/3" imager. 

This will be especially difficult to measure because you need to know both the size of a pixel for a given camera and the lp/mm for the lens - neither of which are generally provided.

Conclusion

Megapixel lens selection matters greatly yet megapixel technical disclosures are lacking for this element. I am looking forward to a discussion to help improve the level of eduction on this.


Related Reports

Selling and Valuing Security Integrators on May 12, 2017
This ia a tutorial in how to (1) determine your security integrator's value and (2) to sell your security integrator. If you own an integrator,...
Technician Personal Protective Equipment (PPE) Guide on May 12, 2017
Technicians encounter multiple hazards when running wires and installing security devices. Wearing personal protective equipment, or PPE, helps...
Varifocal Vs Fixed Lens Statistics 2017 on May 04, 2017
Varifocal camera lenses provide more flexibility at installation time, but come at a higher cost. Fixed lens cameras reduce hardware costs, but can...
Duress Codes For Alarms Systems on May 02, 2017
An alarm system can call for help in the event of an attempted break in, but only if it is armed. If an adversary forces an authorized user to...
Burglar Alarm Strobes Guide on Mar 31, 2017
Strobes provide visual notification of alarm incidents, as sirens are used to give audible notification. Using a strobe gives alarm users and alarm...
Burglar Alarm Sirens Guide on Mar 27, 2017
Sirens are used to alert users to an alarm condition. In this note, we examine how to choose, locate, and install alarm sirens, including Siren...
Glass Break Sensor Tutorial on Mar 21, 2017
Burglars often break glass windows to get into a house. Using glass break detectors in conjunction with alarm contacts is a good way to protect the...
Alarm Panic Switches Tutorial on Mar 16, 2017
Panic switches allow silently triggering an alarm system when it is otherwise disarmed. In this tutorial we explain and contrast the 7 most common...
Environmental Sensors For Burglar Alarm Tutorials on Mar 15, 2017
Intrusion detection systems can be used to alert users to environmental issues. By connecting sensors that monitor the heat, humidity, and...
Alarm Contacts Tutorial on Mar 07, 2017
Contacts are the devices that tell an alarm panel when an entryway is open or closed. The act of opening or closing an entryway, such as a door or...

Most Recent Industry Reports

H.265 / HEVC Codec Tutorial 2017 on May 25, 2017
Since 2013, video surveillance professionals have talked about the potential for H.265. Now, in 2017, H.265 is starting to gain mainstream...
Camera Course Summer 2017 on May 25, 2017
Learn video surveillance and get certified. IPVM provides live online classes, recorded videos, personal help, cutting edge education and...
Most Respected Manufacturer Competitors on May 25, 2017
Manufacturers told IPVM what competitor they most respected. In terms of total revenue, Hikvision, Dahua and Axis are certainly tops but would...
CyPhy 'Unlimited' Flight Time Security Drone Examined on May 25, 2017
Drones face several issues as commercial security platforms - legal restrictions (e.g., in the US, the FAA), costs, and limited flight durations...
Milestone Entry Level Mobile Password Vulnerability Disclosed on May 24, 2017
While many manufacturers have only addressed cybersecurity vulnerabilities after public disclosures were made (or threatened), Milestone has...
How Integrators Use IPVM on May 24, 2017
150 integrators explained how they use IPVM and how it helps them stay informed and improve their business.  The 4 main uses integrators cited for...
Alarm Supervision Guide on May 24, 2017
Burglar alarms can constantly monitor the health of attached circuits, sensors, and devices to ensure that they remain operational. This is known...
Arlo Go Cellular Cloud Camera Tested on May 23, 2017
Totally wireless surveillance cameras are growing but almost all typically depend on a hub and local Internet access. However, many outdoor...
Avigilon New COO James Henderson Profile on May 23, 2017
It has been nearly 2 years since the infamous Bryan Schmode 'resigned' as Avigilon COO. Now, Avigilon once again has a COO, promoting James...
Hikvision Marketer Caught Spamming, Fails at Coverup, Fired on May 23, 2017
A Hikvision marketing employee was caught by IPCamTalk trying to surreptitiously disparage IPVM and IPCamTalk. This is an outgrowth of Hikvision's...

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