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Ghosting when stacking filters

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Daniel Stone
Ghosting when stacking filters
on Sep 14, 2011 at 1:21:38 am

Hi all. I did some research and find some other people have similar problems but there hasn't really been a good solution.

Whenever I stack 2 filters in my 2-stage matter box (usually a hot mirror and ND) I get some major ghosting. I'm not just talking about lens flare, I'm talking about anything white -- a door jam, a window, a car's daytime running lights, a bright reflection... anything white.

I've tried everything - tilting the filters, rotating, taping off all exterior light, swapping the order, etc. The only thing that allows me to stack filters without ghosting is taping them together (like touching) so there's no space at all between the filters.

Is there anything I'm doing wrong? Anything you guys do that helps?

Thanks!


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john sharaf
Re: Ghosting when stacking filters
on Sep 14, 2011 at 1:31:57 am

Daniel,

You're doing everything right; stacking the two filters by taping them together is the accepted solution. Although I have yet to find them, I'm told there are custom filter trays made to facilitate this. If anyone knows a source for these, this is a perfect occasion to chime in.

JS



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Todd Terry
Re: Ghosting when stacking filters
on Sep 14, 2011 at 2:20:39 pm

I've never heard of filter trays like that, John... but that'd be a cool thing indeed. If anyone has a source for something like that, I'd sure like to know it as well.

And yes, Daniel, you're not doing anything wrong... that's just an anomaly that sometimes happens, especially when the filters in the box are too far apart. You might try swapping the filters and changing their "front to back" order and see if it helps.

If it usually happens when you are using a hot mirror plus an ND filter, the easiest (and surefire) solution might be to get some different filters. They make filters that are both hot mirror and ND combined in a single filter (available in different levels of ND). That would totally solve the problem of light bouncing between the glass, since there would be only one filter in the box. The only real downside is that hot mirrors, as I'm sure you know, tend to be pretty expensive as far as filters go.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Jason Jenkins
Re: Ghosting when stacking filters
on Sep 14, 2011 at 3:36:06 pm

[Todd Terry] "The only real downside is that hot mirrors, as I'm sure you know, tend to be pretty expensive as far as filters go."

I have nothing to add here, but hopefully I can take something away. What is a "hot mirror"?

Jason Jenkins
Flowmotion Media
Video production... with style!


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Todd Terry
Re: Ghosting when stacking filters
on Sep 14, 2011 at 3:39:47 pm

A hot mirror is just what they call, for some reason, an infrared filter.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Jason Jenkins
Re: Ghosting when stacking filters
on Sep 14, 2011 at 8:47:03 pm

Thanks, Todd!

Jason Jenkins
Flowmotion Media
Video production... with style!


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Nelson Goforth
Re: Ghosting when stacking filters
on Sep 23, 2011 at 4:27:31 am

A hot mirror is a little different from an IR filter, but the purpose is the same.

A hot mirror filter has a coating on the outside of the glass that reflects IR light. The filter needs to be the outermost piece of glass, and the coated side needs to be on the outside.

A regular IR filter is integral to the glass, rather than being a surface coating, at least the few I've seen.

We've been using a Hot Mirror/1.2 ND combination for our Red camera, since the IR pollution only seems to show up around N9 or so. It'd be great to have one at .9 and one at 1.2, but they ARE expensive.

Red Camera Rental & Indy Features, Denver Colorado.
rockymountain4k.com * 303.506.2456


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Daniel Stone
Re: Ghosting when stacking filters
on Sep 15, 2011 at 5:42:51 am

Excellent! Thanks so much everyone!

Dan


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