Gain / Exposure Snapshots

[rmk8]

This is a bit of an odd one, but perhaps someone can offer some advice (or a camera that would perform better)

We have a number of DS-2CD2T42WD cameras which work excellently during the day, but at night require a fairly high gain to be useful. This completely overexposes license plates (which make up a very small part of the image) but are nonetheless useful.

What we have noticed is that if you reset any exposure related attribute (gain, shutter etc) then as the camera adjusts for a second or so the plate is perfectly readable (see attached)

As a result, there's a cron script running that fires this every few minutes...

#!/bin/bash
curl http://u:p@10.0.0.1/ISAPI/Image/channels/1/gain > gain.xml
curl -H 'Content-Type: application/xml' -X PUT -d @gain_10.xml  http://u:p@10.0.0.1/ISAPI/Image/channels/1/gain
sleep 0.2
curl -o lp.jpg http://u:p@10.0.0.1/ISAPI/Streaming/channels/1/picture
curl -H 'Content-Type: application/xml' -X PUT -d @gain.xml  http://u:p@10.0.0.1/ISAPI/Image/channels/1/gain

this of course results in a completely useless part of video if anything was going on, but for that instant we get a number plate (see attached) which would otherwise be completely invisible.

Anyone got any better ideas (short of a second camera which is overkill in this application) - I had wondered if it was possible (since gain is in software) to set a different gain on the sub stream but it seems not.

 

[Magic919]

I can’t see the attachment to offer any comments.

 

[rmk8]

Never noticed it didn't attach, however it fails when I try now too :/

I just get an error "Oops! We ran into some problems."

Can be found here Dropbox - gainexample.jpg

 

[Phil]

I can't think of any adjustments or settings that would improve this on that camera model.

If you were to replace the camera(s) then the Milesight cameras have a Highlight Compensation (HLC) setting which would enable you to strike a balance and read the number plates: