PPF vs Lighting Variances

By John Honovich, Published Oct 08, 2012, 08:00pm EDT (Info+)

A major flaw in using Pixels Per Foot (PPF) to specify surveillance cameras is how easily the metric is undermined. Theoretically, you should specify a PPF number, say 50, and know that you will be able to capture facial details regardless of the camera or situation.

The great hope of PPF is that it is an independent, cross industry metric. Unfortunately, it is not. In this note, we show a practical example where even modest lighting variances undermine the accuracy of the metric.

*** ***** ***** ** **** * 10MP ****** **** * ************ **** in ***** ******** *********. ** **** zoomed ** *** ********* *** ***** detail *** *** ******** ** *** scene (* *** *) ** *********** differences ** ****** ***** *******. **** a ****:

--

*** ** ******** ******* ******** **** *****. ********* **** *** *** ** compare *** ***** ******* ** ********* portions ** *** *****.

****** *** *** ****** ******* ** zone * *** **** **** ******** than ***** ** **** *, ******* zone * ****** **** **** **** zone *.

***?

******* *** ********* ** **** *** amount ** ***** ** *** ***** and *** ******** ** ***** ****** the ***** ** ****. ***** *** image ** * ***** ** ** fairly ***** ********** - *** *** light *** ***** **** ****** ******** - **** * ** ******, ******** lit, ***** **** *, ********** *** awning ** ******.

****** **** ******* *** ****** **** others ** ***, **** ****** *********, will ******** ***** ********* ** ***** quality, ********** ** * *** *************.

Hurts ********* **** - **********

***** *** ****** ***** ******** *********, megapixel (********** *****-*********) **** *** **** likely ** **** **** ** ** a ********* *******. ***** ********* ******* often *** **** ** ******** ****** areas, ******* ** ** ******* ******* or ****** **** ***** ******, *** larger *** **** *******, *** **** lighting ********* *** ******. *** ******* above ***** **** **** ** * hand ****** ************ ********* ******, **** variances *** ***** ****** ******* ******** notably.

What ** **?

*** ****** ***** ** *********** *** PPF ***** (*.*., ** ******* ** 50, ***.) ** ****** **** **** areas ** * ***** **** **** to ******* *** ***** ** ****** projected *** ** ******** *********. **********, this ** *** **** * ******** camera ******* *** * *********** **** of *** *** *********** (****** ******* that *** ****** ** *** ** night **** ******* *** ******** **** minimize ***** ********).

****, ** ******, **** *** ***** when ******* **** **** ********* **********, like *** ***** ** ****** ********. See ****** **** ******* *** ****.

Lessons **** **** *****

**** ***** *** ****** ** ** excellent ********** ****** * ***** ** the **** ******** ************ ****** (*** tip *** *** ******* *** *** specific ******* *****).

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

ppf results

*** ***** ****** ** **** *** cannot ********** **** *** **** ****** per **** *** **** ** ******* a **** ***** *** ********** *** scene **********. *** ******* ***** ** an ********* ******* ** ****. *** might **** '***** **** ****** ** it' ** ********** * ****** ****** (say ***** ******* ** *****) *** it's ***** ** ********* (*** *********** inefficient) *** ** ***** **.

*************, **** ***** **** ***** ** no **** *** *** ** *** want ** **** ******* **** ******* details *** *** '*****' ******. ********* evaluating **** ********** *** ******* *** right ******** ************ ** *********.

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