The PPF / PPM Video Surveillance Guide

Author: IPVM Team, Published on Dec 23, 2016

Pixels per foot / Pixels per meter is the most fundamental and valuable, though imperfect, metric for specifying video surveillance image quality.

In a single number, this metric (e.g., 10ppf, 40ppf, 100ppf) conveys important information about what the projected quality that a camera can provide.

The image below, taken from our Camera Calculator, demonstrates examples of common pixel per foot (ppf) levels:

PPF Established Metric

PPF has become a critical established metric for several reasons:

  • Broad camera manufacturer support: Most major manufacturers use this metric.
  • Common A&E specifications: Architects and engineers who plan large projects regularly use PPF / PPM as the basis for their designs and surveillance plans.
  • Need for Something: With so many resolution options today (from 1MP to 12MP and beyond), the old metrics which used percentage of screen covered make no sense. PPF has filled this void.

The Goal of PPF

PPF is a single metric (e.g., 10, 50, 90, etc.) that when specified should deliver a specific level of quality. For example, the parking lot camera must deliver 50 PPF. Instead of guessing or just specifying more resolution, using this metric should enable selection of the ‘right’ resolution for the scene. The final image, following the PPF metric, will then deliver a predictable level of quality.

PPF Problems

Alas, PPF suffers from many problems that must be factored in:

  • Assumes even lighting and ignores the impact of bright sunlight
  • Assumes day time lighting and ignores the impact of night time / low light viewing
  • Disregards differences in lenses and compression
  • Disregards that image quality needs are subjective and debatable
  • Fails to specify related and critical metrics to complement PPF

Despite this, PPF does have value for estimation and planning. It just cannot be used blindly or simplistically. Inside the PRO Member’s section, we explain:

  • How to calculate PPF
  • How to recognize PPF limitations and make adjustments
  • How to best use PPF productively

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PPF *********** ******

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The **** ** ***

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PPF ********

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PPF ** ***

****, ** *** *** ********** **** ******, *** ********* *** metric **********, ****** *** ***** (***), ** ****. *******, *** is ******** ****, **** ** **** ******* ************ ** *** metric ******.

*** *********, *** ***** ***** ***** **** ******** *** ****** for **********. **** **** ******* ****** ************** ******** ****** ************, ** ******** ** ******** / ***.

How ** ********* ***** *******

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Horizontal ***** *****

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**** *** ********** ***** ****** *** ****** ***********:

**** **** ** ******** **** ** **** *** ***** ***********.

Selecting *** *****

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**** ** ***** **** *** ** '*****', *** ** ******* on ******** *******.

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** ***** ** *** ***********, ** ********* ***** ***** ****, so **** *** ** *** ************* **** ***.

PPF *******

**** *** **** ********** *** ********** ****** ** *** ****** chosen *** ******** **** *** *****, *** ** ****** ********.

**** *** * *** ********:

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PPF ********* ** *** ***** *** ******** **** ****** *********

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******* *********, *** *** ***** ********* ** ** ***** *** FOV, **** *****. ******** *** ****** ** *** *** *****, we *** *** *** ********, *********** ** ***.

*** *** *** **** *** ******** ** ******* ****** **********.

Fisheye ***** ** **** ******

*******, ****** ** ***** ** **** ***** **** ***** ******* panoramic ******, ** *** ***** ************, **** ****** **** ******** cameras.

***** *** (*) *** ******* ** ** *******, *** * fisheye ********* (*** ****) *** *** ***** ***** * ~**° HFoV. ******* *** **** ** *** ** ******** ** **** away **** **** ******:

  • **** * *** *********, ** ** **** **** **** *** camera, *** *** ** ~**
  • **** * *** '************' **° ****, ** ** **** **** from *** ******, *** *** ** ~***

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*** *** **************** ********* ****** *********** **** *******.

Recognizing *** ***********

**** ***** *********** ***, ***** *** ******* ****** ***** ****** the ********* ******* ** ****** *********. *****, ** ******:

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  • *** ***** / ***** **** *******
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Wide ******* ***** ***********

*** ******* *** ****** *** *** **** *** *** ********* power *** **** *************. *** ******* ** ****** ****** ********* / ******** ** * *** *******. ** *** ***** *****, both ******* **** *** **** **********, ***** *** **** *** and *** ***** ** *** **** ****:

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**** ** ** ***** **** ** ****** **** **** ******** variations ** ***** ******. ** *** ***** *****, **** * has * ***** *** **** **** * *** **** * clearly ******** **** ***** ****** ******* **** * ** ** a ****** **** **** *** ****** ********* ** ****** ***********.

*** ****** ******** ******* **** *********** ** **** ******* ***** *** ***** *******.

Low ***** ***********

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** *** ****** **********, ** ******* ******* ***** ** **** world *** *** ***** ****** ** **** **** **********, **** PPF ********* ** **** **** ** ***** ****** ***** *******' parameters.

Differences ** ***********

******* *** ********* ******* **** *** ** *********** ***** ********. Even ** *** **** ********** *** *** **** ***** *** used, *** ****** ** *********** *** **** *******. ***** ************ that:

** ***** **** ***** *'* *** ** *** ***** **** image *, *** **** ** *** *** ****. *** *** less *** **** ***** * *** **** ** *** *** case. **** ****** *** ***** **** *** **** ******, **** the **** ********** ***** ********* *********** ** ***** *.

****** ** *** ********* *********, ************* *** **** ********* ******* compression ********, ** **** ** ********* *********** *** ***** ******* quality ******. ******* ****** *** ***** ****** ************ *********** ************* ******* ** ***** ******** *** ************ *****.

***** ****** ** ******* ** ***** *********** ****** ********** ************* ********* ** ***** ***** ******** ******. *** ******** ******* / *********** *********** **** ******* ** *********** *** *** *******.

Lens ***********

**** ***** **** **** ******* *** **** * **** ********** in ***** *******, ********** ** *** ****** ********. *******, ** our *****, **** ******* ** ****** * ***** *******, ******* fine ******* *********** ***** *** *********** ** **** ******. ***** factors, **** ***-****,******, *** ********** ************ *** *** **** ****** ** ****** image *******.

Subjective ***** *******

******* *** **** ********** ******* ** *** ** *** ********** the '*****' ******* ***** *** **. **** ** '****** ** in *** *** ** *** ********', *** ********** ****** *** think * ***** ******* ***** ** **** ****** ** '********' a *******, *** ******* *** ******* ************* **** ****** ** target *** ********.

*** *******: * ******** ***** ** ****** * ***** *******. Which ** *** ***** *** ****** ***** ** *****?

***** **** ** **** **** ****** ******* *** *** ** them **** ** ***** ** *******, **** ***** ****** *** 18 ** ** *** ******, ** **** **** **** **** just * ****** '****', **** **** **** ***** *******.

*** **** ********* ******** ****** **** ******** ******* *** **** pixels *** ****** ** ******** * ******** ******. ******* *** images *****:

**** ****** **** *** *** ~** *** ** *** **** is *** ***** *** **** **** **** * '*******' *****. Others **** **** ** **** ******, ********** ** *** ****** is *****, **** ** ** ******** ** ********.

********** ** **** ** '******' ****** ** ******, *** ***** to ****** **** *** ***** / ******** ***** **** **** think ** **********.

Related / ******** *******

**** ********** *******, *** ***** **** *** ******* ****** *********** to ******** ****** *******, ******* ** ********* ** *********. **** using ***, ******* ******* **** ** ****:

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FOV **** **********

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** *** ****** **** ****, *** **** ********* ****** *** performance ********* **** ** *** ******'* *** ***** *** *** performance. ********, ***** ******* **** ***** ******* **** ****** ******** and *** ***** *** *** **** ****** ** ****** ******** a '****** *** *****'.

Larger **** **** *********

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** ******* ***** ********** *** *** ***** ***** ** ** can ****** ******** ** *** ***. *** ********, ***'* *** you **** ***** ****** * *** **** **** ****. ** do **, *** **** **** **** ********** ******. * ****** 14MP ****** *********** **** (** ** *** ~**** ********** ******) as ***** (*) *** *******. *** **** ******** ***** ***** be (*) ***** *******. ***** *** ***** *** ** ******** less (****), *** ******* ******* *** ** ******** ** ***, low *****, ***** ****, ***** ******* *******, ***.

PPF ********** ******* ** *************

**** *** **** ** ****, *** ****** ******* ** ************ PPF **********.********:***** ******* ****** ******, **** ******** *** ** *** ****** in *** ****** ** ****** ******** ** **** ****** ********, which ** ****** ************.

****** **********:

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  • ******** ******* / ****** *** **** ** ****** (******, ***) is ***** *** *** *** *********** *******:************* ********* ********* ******* ** *** ** ***. **** ** fairly ********* ** **** ** ******** ** *****.
  • *** ******* / ********* ****:************* ******* * - ** ***. ** *******, ******* ** this *****, ** *** ** **** **** ** **** ******* out ****** *** ******* **** **** **** *** ***** ** if *** *** ******* *********. ** ******, **** **** ******** ideal ********. *** ** ***, ** *** **** **** **** 10 ***, *** *** ****** ****** ** **** *******. *******, some ********* ******* **** * *** *** ** ********, ** may ***** ** ****.

[****: **** ***** *** ********** ******* ** **** *** *** revised ** ****/**** ** ******** ******* ******* *** ******* ****** examples **** *** **** ****** **********.]

Comments (11)

Undisclosed #1

12/23/16 04:01pm

However, in our tests, lens quality is rarely a major concern, despite fine quality differences which are perceptible in some lenses...

Has there been a specific test of lenses and their effect on apparent PPF? Some tests have indicated that in certain cases there might be substantial differences, A Major Flaw in Long Lenses and PTZs Found.

Plus with imager pixel density increasing, lenses are needed to have higher MTF.

Avatar

Ethan Ace

IPVM | In reply to Undisclosed #1 | 12/23/16 04:24pm

You raise a good point. We'll add more info about long lenses and clarify.

Gavin Botha

12/24/16 03:26am

Great article.

James Drymiller

12/31/16 09:24pm

Note, we use PPF throughout this report, but sometimes the metric equivalent, Pixels Per Meter (PPM), is used. However, PPF is commonly used, even in many regions standardized on the metric system.

This bias for anything non-metric forever bemuses me.

Setting aside your 'regional' comment for just a moment, there are only 3 countries in the world not using the metric system. And with no offense to Burma or Liberia, it's the USA that you are acquiescing to here. So I ask you (IPVM) to reflect on PPF versus PPM. As 'the world's leading video surveillance information source, IPVM provides the best reporting, testing and training for 10,000+ members globally' [my emphasis on the areas in bold], who are you serving? What is the more exact measurement tool?

You say, 'PPF is commonly used, even in many regions standardized on the metric system. I wonder what you base that comment on? More importantly, if that is true, could the reason be because PPF is what we are force fed?

The US National Institute of Standards and Technology (NIST) has a very interesting paper on the subject of metric systems in the USA at https://www.nist.gov/sites/default/files/documents/pml/wmd/metric/1136a.pdf

Thanks for your consideration and Happy New Year.

John Honovich

IPVM | In reply to James Drymiller | 01/01/17 01:03am

James,

Our calculator has long supported metric and actually checks the country for each visitor defaulting to metric for those countries who use metric.

We will add in references to PPM values as well as PPF for all pictures / graphics after the New Year's and update the post.

John Honovich

IPVM | In reply to John Honovich | 01/06/17 03:18pm

James, all, we added PPM measurements to the images inside the report. Thanks.

Avatar

Eddie Moss

IPVMU Certified | 08/08/17 10:32pm

Can anyone explain why the Horizontal Pixel count of 2592, for 5MP resolution, is less than the figure of 2688, for 4MP resolution?

This question is in reference to the table on page for of this tutorial.

John Honovich

IPVM | In reply to Eddie Moss | 08/08/17 10:37pm

Eddie, good eye.

The reason that 5MP has a lower horizontal pixel count than a 4MP camera is the difference in aspect ratios, i.e., 5MP cameras are 'taller' than 4MP ones:

5MP - 2592 x 1944

4MP - 2688 x 1520

Related - Aspect Ratio 16:9 vs 4:3 Shootout

Also, 3MP cameras have slightly greater vertical pixel count but much narrower horizontal one, i.e., 3MP - 2048 x 1536

Undisclosed End User #2

05/28/18 05:18pm

Give a better idea of ppm.

Avatar

Brian Rhodes

IPVMU Certified | In reply to Undisclosed End User #2 | 05/28/18 10:32pm

I want to help, but I don't understand the question. Can you expand?

Undisclosed #3

11/20/18 11:29am

Clear explanation of changes in HFoV and change of PPF according to difference parameter. Great information.

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