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ND Hot Mirror?


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#1 Jason Hinkle (RIP)

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Posted 05 January 2010 - 10:30 PM

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?
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#2 John Sprung

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Posted 06 January 2010 - 02:53 PM

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.
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#3 Jason Hinkle (RIP)

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Posted 15 January 2010 - 01:19 AM

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!
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#4 Satsuki Murashige

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Posted 15 January 2010 - 02:57 PM

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.
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#5 William Coss

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Posted 15 January 2010 - 07:32 PM

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
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Visual Products

Metropolis Post

The Slider

rebotnix Technologies

Gamma Ray Digital Inc

CineLab

Abel Cine

New Pro Video - New and Used Equipment

Glidecam

Ritter Battery

FJS International, LLC

Aerial Filmworks

Broadcast Solutions Inc

Paralinx LLC

Technodolly

Media Blackout - Custom Cables and AKS

Wooden Camera

Tai Audio

Rig Wheels Passport

CineTape

Willys Widgets