ant_thomas
Posts: 115
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IR to Visible "filter"/processing - Pi NoIR

Thu Oct 31, 2013 12:56 pm

This may sound like a silly question, and I realise it might not get many or any answers...but...

Does anyone know of any software filters/processing to try and convert an image from the NoIR camera module to look more like a visible light image like the original camera module. If imagemagick can do it, all the better.

Reason being, I would like to be able to make a setup that uses the NoIR camera 24/7 but for the night an IR light source will be turned on to illuminate the scene. I'd like to have the "day" images looking as close to day/visible as possible with the night time ones taking advantage of the IR ability.

Only other idea is some sort of mechanical addition to move a filter in front of the camera module that blocks the IR.

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redhawk
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Re: IR to Visible "filter"/processing - Pi NoIR

Thu Oct 31, 2013 1:29 pm

Not really, you could probably improve white balance with software but the effects of infrared light is too severe to be compensated without an IR block filter.

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jamesh
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Re: IR to Visible "filter"/processing - Pi NoIR

Thu Oct 31, 2013 2:06 pm

Most security cameras have a mechanical IR filter that drops down during the day.
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ant_thomas
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Joined: Fri May 04, 2012 4:33 pm

Re: IR to Visible "filter"/processing - Pi NoIR

Thu Oct 31, 2013 3:33 pm

That answers that one, thanks for the replies!

StephanB
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Re: IR to Visible "filter"/processing - Pi NoIR

Thu Oct 31, 2013 3:43 pm

Yes agreed, mechanical moving an IR filter .During the day you filter out IR to get normal photos and at night you do not use the IR filter such that you have better night vision but the colour is a bit strange. I do not think you will be able to undo IR in software. The reason I say this is that IR hits the blue detectors do what you get with a NOIR Filter, camera is
Red detector is triggered on Red light
Green detector is triggered on Green light
Blue detector is triggered on Blue and IR light
(Basically this is a fault, as the Blue detector should trigger on Blue only. To correct this makers put in a filter to remove the IR)
The reason IR hits the blue is to do with the Harmonics of its frequency. That is most of the IR does not hits the blue but as per harmonics some of the IR triggers the blue.

In daylight if you want to avoid the IR you need an actual IR filter to remove the IR from the blue and you then have a normal camera.
Hope this helps

poing
Posts: 1132
Joined: Thu Mar 08, 2012 3:32 pm

Re: IR to Visible "filter"/processing - Pi NoIR

Thu Oct 31, 2013 4:10 pm

StephanB wrote:Yes agreed, mechanical moving an IR filter .During the day you filter out IR to get normal photos and at night you do not use the IR filter such that you have better night vision but the colour is a bit strange. I do not think you will be able to undo IR in software. The reason I say this is that IR hits the blue detectors do what you get with a NOIR Filter, camera is
Red detector is triggered on Red light
Green detector is triggered on Green light
Blue detector is triggered on Blue and IR light
(Basically this is a fault, as the Blue detector should trigger on Blue only. To correct this makers put in a filter to remove the IR)
The reason IR hits the blue is to do with the Harmonics of its frequency. That is most of the IR does not hits the blue but as per harmonics some of the IR triggers the blue.

In daylight if you want to avoid the IR you need an actual IR filter to remove the IR from the blue and you then have a normal camera.
Hope this helps
Is this a so-called 'Hot Mirror' filter (blocks both UV and IR)?

SnowLeopard
Posts: 106
Joined: Sun Aug 18, 2013 6:10 am

Re: IR to Visible "filter"/processing - Pi NoIR

Thu Oct 31, 2013 4:15 pm

ant_thomas wrote:Does anyone know of any software filters/processing to try and convert an image from the NoIR camera module to look more like a visible light image like the original camera module. If imagemagick can do it, all the better.
My Motorola XT720 does not have an IR filter (which came in handy when building an infrared remote for just confirming if the LED was lighting up) but produces perfectly normal looking images. One can only assume the processing is being done in software somewhere.

justken
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Joined: Sat Nov 16, 2013 1:53 am

Re: IR to Visible "filter"/processing - Pi NoIR

Sat Nov 16, 2013 2:04 am

I have a follow on question to this. I am wanting to use the NoIR to look at black lighted Scorpions. Does anyone know if this will work?

I can visually spot a scorpion on my outside walls, 15-20 feet away with my small UV flashliight at night, but the regular cameras and web cameras if have tried has been bad. Their response to a the fluorescence under low light has really really been poor from even a foot or two away.

Ken

TheRealMrChips
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Re: IR to Visible "filter"/processing - Pi NoIR

Sat Jul 30, 2016 12:05 am

I know this posting was back in 2013, but for those reading in the future I at least have a partial solution:

When using the Pi-NOIR camera with the raspistill application, you can at least get a lot closer to the naked-eye image by modifying the white-balance setting. You will need to play around to get the right settings for your situation, but in my case I have a webcam that is taking weather photos in my Southern California neighborhood.

When the weather is sunny, I have found that setting -awb tungsten helps a make things much better. The main issue will always be things like foliage. There is no way to get foliage back to green using a simple global digital filter after capture. Plants will always take on a purple hue. Otherwise this helps a LOT.

I would imagine the same would go for any other application or filters that you would apply after-the-capture to such images from the NOIR. Any filters that can adjust the white-balance can then be tweaked to get something closer to real-life.

I hope this at least helps a bit! Keep on hacking.

Examples:
image-tungsten-awb-800pxw.jpg
AWB = Tungsten
image-tungsten-awb-800pxw.jpg (52.68 KiB) Viewed 4111 times
image-auto-awb-800pxw.jpg
AWB = Auto
image-auto-awb-800pxw.jpg (62.38 KiB) Viewed 4111 times

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