IR Filters question.

[Jamie Smith]

Hi

I was hoping someone could let me know what is the purpose of using IR filters with the RED. Is it essential? do you need them in all kinds of light? what does it achieve?

any help would be much appreciated.

cheers

jamie

[Tom Mitchell]

Hi Jamie. silicon sensors have a sensitivity in the the IR range. though the red is filtered to some degree against this, it still picks up some.

The camera as you know records in 3 Channels and the combination on the three give you your resultant colour. But the red channel also picks up IR light which the human eye dose not. so this causes the camera to get more exposure in the red channel when is should not. in normal lighting conditions it is not really a issue most of the time.

but anything with a heat source like fire, cigars, or a hot day. Is going to give more abundant IR light and there for you will start to see the effect.

When you use ND filters, they only filter the Visible spectrum. so whilst your reducing the visible spectrum the IR light is relativity unaffected therefor when you stick a lot of ND on the camera (0.6+) you will notice IR pollution. The way this is combated is to stick a HM or ND combo filters. (HM should be placed reflective side out in the most furthest away from the lens in order)

The effect adds a purple/pink hue to your blacks. I remember shooting a glass of red wine on a hot day, and the liquid looked bright pink through the camera.

cigars/cigarettes can have a pink/purple look to them too.

is it essential? no, but you might not like the look it produces. so in most cases people use them.

[ericyoung]

As Tom said. Although you don't need them all the time, as soon as you do you REALLY need them!

Basically if the picture colour looks completely different to what your eyes are seeing, and assuming you've already checked you've setup sensible white balance and monitoring, then you may have to use an IR filter. It's easy to check, just put your IR filter in front, and if all the colours look right again then you have IR pollution of your image. IR can also make your pictures look soft as the IR image is usually slightly out of focus compared to the visible spectrum. If the IR filter makes no difference, then you may have a different problem with settings or monitoring.

[Jamie Smith]

Thanks alot for your help guys.

jamie

[Mike Prevette]

Check out my original thread here for examples and detailed explinations.

http://www.reduser.net/forum/showthread.php?t=9141

[Tom Mitchell]

Check out my original thread here for examples and detailed explinations.

http://www.reduser.net/forum/showthread.php?t=9141

Yes Awsome, check it out, has pictures to show you what it is, so you can look out for it.