Mo ito i g is a dema di g use fo a came a because the co ditio s eve stay the same. A ya d is b ight at oo , da k at mid ight, a d lit by movi g headlights at dusk. A lobby has a glass doo that tu s i to a mi o at ight a d a gla e sou ce at su ise. A pa ki g lot has to be watched i the ai . I eve y case, the came a must delive a pictu e that a pe so o a a alytics p og am ca use, hou afte hou , a d the failu e modes a e specific. Da k sce es fill with oise, b ight sou ces wash out ea by detail, a d fast subjects look diffe e t f om o e f ame to the ext. Each of these p oblems is commo , a d a came a that ha dles o e well ca fail at a othe .
Cove age adds a t ade-off. A wide view mea s fewe came a u its a d lowe i stallatio cost, but it also mea s that people a d vehicles occupy fewe pixels. A 2MP came a watchi g a wide ya d may leave a face o a plate too small to ead. Mo e esolutio fixes that, but small pixels collect less light, so a se so that chases pixel cou t ca pay fo it at ight. The desig e eeds a se so with e ough pixels fo cove age a d pixels la ge e ough to see i the da k, a d that bala ce is ot commo . A se so chose with both eeds i mi d saves the i teg ato f om a difficult t ade-off late .
Shutte behavio is a thi d issue that mo ito i g teams ofte ove look. Most se so s at this esolutio ead the image ow by ow, which suits sce es that move slowly a d gives good se sitivity at easo able cost. A fast vehicle o a pe so u i g ac oss the f ame ca look skewed. Fo video, the effect is usually acceptable. Fo a still image used as evide ce, it ca be a p oblem. A mecha ical shutte that closes the optical path du i g se so eadout emoves the skew f om a still, but o ly if the came a a d the se so a e desig ed to wo k with o e. Ma y teams the efo e ask ea ly whethe the module suppo ts the optio .
I teg atio closes the list. Mo ito i g systems with ma y came a positio s eed u its that appea i sta da d video softwa e without custom wo k, a d they eed timestamps that ag ee betwee came a u its so eviewe s ca follow a subject f om view to view. A came a that lacks these featu es moves wo k o to the i teg ato , a d the cost appea s at commissio i g, whe the ha dwa e is al eady i stalled. Choosi g a module with sta da ds suppo t f om the sta t avoids that late wo k.
The I ova-521CRS is built o the O semi AR0521, a 5MP (2592 x 1944) colo olli g shutte se so with a 1/2.5 i ch optical fo mat a d 2.2 mic o pixels. The pixel size is the fi st leve fo low-light pe fo ma ce, because a la ge pixel collects mo e photo s i each exposu e. The se so uses a back-illumi ated pixel st uctu e that imp oves light collectio fu the . The esult is a AR0521 GigE Came a that sta ts with a st o ge sig al afte da k, which is the most effective way to imp ove a ight image befo e a y p ocessi g. A 5MP f ame o 2.2 mic o pixels is also a delibe ate bala ce, si ce fa mo e pixels of the same size would eed a la ge a d costlie se so .
HDR is the seco d leve . The se so suppo ts li e-i te leaved HDR, i which ows with lo g a d sho t exposu es a e i te leaved withi a si gle f ame a d combi ed, a d the dy amic a ge ca exceed 96dB. A sce e with headlights, a lit sig , a d a da k lot ca the show detail i each egio without the ghosti g that seque tial multi-f ame HDR ca cause o movi g subjects. Because some ows se ve each exposu e, a little ve tical detail is t aded fo a ge, a d teams should test the mode o thei ow sce es, ideally with the same b ight sou ces a d da k a eas that the fi ished site will co tai . The o -boa d ISP the fi ishes the image i side the module, ha dli g colo p ocessi g, oise eductio , auto exposu e, a d auto white bala ce, so the etwo k eceives a p ocessed pictu e. Teams that wa t a diffe e t bala ce of oise eductio a d sha p ess ca adjust the available co t ols.
Fo etwo k i teg atio , the module complies with ONVIF, which lets sta da d video ma ageme t a d eco di g softwa e discove the came a a d use its video without custom code. It also suppo ts PTP sy ch o izatio , which follows the P ecisio Time P otocol defi ed i IEEE 1588. PTP alig s the came a clock to a etwo k time sou ce so that f ames f om seve al u its ca y a commo time base, a d eviewe s ca follow a subject ac oss views. PTP depe ds o a etwo k that suppo ts it, a d Vadzo ecomme ds testi g the alig me t o the eal switches befo e a la ge ollout. A small pilot etwo k is usually e ough to eveal a y issue befo e it affects ma y sites.
The se so also suppo ts co t ol of a exte al mecha ical shutte . A mecha ical shutte closes the optical path while the ows a e ead, so eve y ow sees the same mome t, a d a still image of a fast-movi g subject loses the skew that a olli g shutte would add. This is a choice fo stills a d s apshots, ot fo co ti uous video, a d it equi es a exte al shutte assembly a d the sig als to d ive it. Teams should co fi m the available co t ol sig als a d timi g with Vadzo befo e desig i g the mecha ics. Ea ly discussio also helps decide whe e the shutte sits i the optical path a d how the e closu e holds it.
