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

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...
Multipoint Lock Access Control Tutorial on Oct 17, 2017
Doors are notoriously weak at stopping entry, and money can be misspent on wrong locks that leave doors quite vulnerable. While closed and locked...
Exporting Video Surveillance Tutorial on Oct 05, 2017
Exporting video surveillance is important when incidents or crimes occur. However, there are multiple ways to export video which have their pros...
Delayed Egress Access Control Tutorial on Oct 04, 2017
Is it ever legal to lock people into a building? The answer is: Yes... under specific situations. With so much of access control driven by life...
Propped Doors Access Control Tutorial on Sep 28, 2017
Doors should keep 'bad guys' out. One of the most basic problems with doors is people propping them open: Even worse, door propping...
Automatic Door Operators For Access Tutorial on Sep 20, 2017
Opening and closing doors might sound simple, but it takes a high-tech piece of door hardware to pull it off. Integrating automatic door operators...
Master Keying Tutorial on Sep 14, 2017
Mechanical keys are the most fundamental, albeit unsophisticated, form of access control. Like access control, Master Keying allows large scale use...
Fail Safe vs. Fail Secure Tutorial on Sep 13, 2017
Few terms carry greater importance in access control than 'fail safe' and 'fail secure'. Access control professionals must know how these concepts...
Dahua 4K IR PTZ Tested on Aug 21, 2017
4K has made its way to IR PTZs. In this report, we examine the Dahua 6AE830VNI, a 4K PTZ with 30x optical zoom, 200m (~650') integrated IR, and...
IP Camera Specification / RFP Guide 2017 on Aug 14, 2017
RFPs are hard. Do them 'right' and it takes a lot of knowledge and time. Do them 'wrong' and you can be (a) unwittingly locked into a specific...

Most Recent Industry Reports

Camera Multi-Streaming Usage on Nov 22, 2017
IP cameras typically support multiple streams, allowing a single camera to transmit multiple streams at different resolutions, frame rates and even...
Law Breaking Longse Enters USA on Nov 22, 2017
Longse has established itself as world class, at least in spamming the industry, ripping off Milestone and Video Insight as well as Hikvision. But...
Amazon Key In-Home Package Delivery Examined on Nov 21, 2017
Interesting idea or invitation for criminals to rob you? Amazon's recent announcement of Key, a service that will help manage visitors, welcoming...
Top Maglock Provider Warns Against Using Maglocks on Nov 21, 2017
Do not buy my company's product. It sounds strange indeed, but a senior Allegion consultant stated that maglocks should not be used in common...
CBR vs VBR vs MBR - Surveillance Streaming on Nov 21, 2017
How you stream video has a major impact on quality and bandwidth. And it is not simply CODEC choice (e.g., H.264 vs H.265). Regardless of the...
Hikvision Chinese Government Owner CETHIK Exposed on Nov 20, 2017
Hikvision deceives about its Chinese government ownership. Contrary to their claims about 'independence' and simply having 'shareholders' that are...
Dahua Hard-Coded Credentials Vulnerability on Nov 20, 2017
A newly discovered Dahua backdoor is described by the researcher discovering it as: not the result of an accidental logic error or poor...
Panasonic Unified Surveillance Strategy Analyzed on Nov 17, 2017
Panasonic is now a "Unified Surveillance" offering, as their ASIS 2017 booth proclaimed: Looking to make a comeback in the security industry,...
Amazon Cloud Cam Is Poor (Tested) on Nov 17, 2017
Retail behemoth Amazon has entered the surveillance market with the Amazon Cloud Cam, the eyes of its just-announced Amazon Key delivery...
Nest Secure Alarm System Tested on Nov 16, 2017
Google's expansion continues, this time into home security with their Nest subsidiary's move into alarm systems. They paid more than a...

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