ND Hot Mirror?

[Jason Hinkle RIP]

I just got a budget .9 ND filter on eBay and when it showed up it looks almost like a 2-way mirror. I hadn't really heard of this before but I did some reading about "hot mirror" ND filters. Is that likely what I have?

 

The mirror effect is pretty strong, it makes me wonder if I need to take any special precautions when using this to avoid reflecting back into the lens? Do I need to press the lens against the filter, or tape up the matte box to prevent any crack of light? Or is it not that sensitive? any special precautions?

[John Sprung]

Yes, that does sound like a "hot mirror" ND. That's a good thing if you ever want to use it on a Red camera, there are a lot more such ND's being made just because of the Red's IR sensitivity.

 

Reflections off the back of any filter can be a problem, especially ND's like this. Check with a flashlight, and tape up any light leaks you find.

 

 

 

 

 

-- J.S.

[Jason Hinkle RIP]

Yes, that does sound like a "hot mirror" ND. That's a good thing if you ever want to use it on a Red camera, there are a lot more such ND's being made just because of the Red's IR sensitivity. Reflections off the back of any filter can be a problem, especially ND's like this. Check with a flashlight, and tape up any light leaks you find.

 

cool thanks!

[Satsuki Murashige]

The mirror effect is pretty strong, it makes me wonder if I need to take any special precautions when using this to avoid reflecting back into the lens?

Just make sure the mirror side is always facing out away from the lens, and that you use it in the front-most tray of your matte box in front of any other filters. And use donuts.

[William Coss]

I just got a budget .9 ND filter on eBay and when it showed up it looks almost like a 2-way mirror. I hadn't really heard of this before but I did some reading about "hot mirror" ND filters. Is that likely what I have?

 

The mirror effect is pretty strong, it makes me wonder if I need to take any special precautions when using this to avoid reflecting back into the lens? Do I need to press the lens against the filter, or tape up the matte box to prevent any crack of light? Or is it not that sensitive? any special precautions?

 

Sounds like a Pancro dichroic ND filter to me. They have made them for decades and it just may not be an IR "hot mirror". Due to the fact that these are relatively new on the market, it should say so on it, if in fact it is. Pancro's website explains it all, i.e., front surface.

 

Bill