IR Filter/Hot Mirror
Posted 22 November 2009 - 12:10 AM
Posted 22 November 2009 - 10:23 AM
While this primarily happens outside you could use it inside if you're using a lot of ND on the camera inside (though can't think of why you would?). Rule of thumb; when you get into double digit ND you should consider an IR.
Posted 22 November 2009 - 12:46 PM
When you stack a lot of ND filters over the lens because of extreme levels of sunlight outside, a lot of visible light is blocked but infrared light is still passing through, so the proportion of visible to infrared light shifts in favor of more infrared. You then get infrared pollution in your blacks and certain colors.
UV is blocked by glass, different amounts depending on the glass, so the problem becomes worse when you aren't shooting with any filters outdoors, and UV tends to show up as exaggerated atmospheric haze. It also tends to be heavier on clear days at high altitudes.