Some Hot Mirror Questions

[A.J. DeCosta]

I'm shooting my second student project on the Red. The first time I had some IR pollution in my outdoor shots and it messed up some colors. This time around I learned about the hot mirror filter and also heard that the new build fixes the issue a bit. Does the IR filter change the image at all (color, etc) if no infrared light is coming through? I dont want to find myself leaving the filter in outside and it changing colors or such.

 

[Dan Hudgins]

Cast

Cast

Does the IR filter change the image at all (color, etc) if no infrared light is coming through?

Some IR filters have a slight greenish cast by transmitted light, so to make color correction easer I would leave the IR filter for all shots, unless you need to use a very wide angle lens, then you might need to take it out if you are using an interference filter since they do not work as well can the color cast and IR filtering will vary accross the frame more at the center and less at the corners. You can use an IR absorbing filter for wide angle lenses.

The amount of RED light cut depends on the IR filter used, some cut more RED than others, with those you can correct with a RED CC gel filter or in post with the CC software.

You should also use a UV blocking filter since UV can be out of focus and make a bluish halo around things with some lenses. A pink "skylight" filter may offset some of the loss of RED from the IR filter.

Put the interference surface facing out, although some may tell you it does not matter, if it is a near cut filter it might reduce reflections off the other filters.

 

[Stephen Strangways]

Hot Mirror/IRND/Mirror ND Filter Matrix Part 1
Hot Mirror/IRND/Mirror ND Filter Matrix Part 2
Hot Mirror/IRND/Mirror ND Filter Matrix Part 3
Hot Mirror/IRND/Mirror ND Filter Matrix Part 4

Personally, I use a Schneider TRU-CUT IR-750 whenever I get to .9 or more of ND.

 

[Jay A. Kelley]

I'm shooting my second student project on the Red. The first time I had some IR pollution in my outdoor shots and it messed up some colors. This time around I learned about the hot mirror filter and also heard that the new build fixes the issue a bit. Does the IR filter change the image at all (color, etc) if no infrared light is coming through? I dont want to find myself leaving the filter in outside and it changing colors or such.

We dedicated a specific module to this in the RED 101 DVD...

It can be an issue.

www.red101dvd.com

Jay