MAJOR Issue with HVX and ND filters

smelni

smelni

Veteran
I am currently shooting a feature with the HVX and came upon a very strange problem . I hope someone here can shed light on this because this bit us hard today.

We were shooting a scene that would have been over f5 so we wanted to use ND filters in our mattebox - i have a .3,.6 and .9 from tiffen 4x4.

ok - here is the strange thing - the ND filters changes colors in the scene selectivly. Skin tones seemed to remain ok. But dark green towels turned magenta, and the white walls turned pink ONLY at the hottest spots. Any speculation as to why would be greatly appreciated - the footage may be unusable since other shots had the true colors.

We got bit by this because our panny cable for composite monitoring cut out in the red channel so we couldnt properly monitor for a bit.

Any help here?
 
:Drogar-BigGrin(DBG) Try smoking less pot

Seriously, I've seen some highlights roll off slightly redish but I've never seen a green object turn magenta. I'd check you component cable again. Sounds like you lost a color, either that or your cameras broken, no ND filter will reverse colors.
 
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I have had something like this happen with sunglases. I have a pair of custom made glacier glases with really dark lenses. With those I sometimes see colors on objects whic look BLACK with naked eye or with other dark glasses. With some colors/materials all kinds of strange color shifts occur. Thus I believe you, but do not have an explanation. Like to hear one.
 
thanks for the replies everyone.

We tried white balancing before and after adding the filter. Also cannot use the built in sinces it is 8 stops and we needed about 2 stops of control.

The color shift from green to magenta was dramatic - However, at a cursory glance skin tones were ok.

Same issue with all the NDs, .3,.6, .9

I will post screen grabs tomorrow - maybe that will help someone figure it out - going to set now otherwise i would do it today,.

Arrgggghhh very frustrated - hope i dont need the NDs today.
 
The built in ND filters are 3 (labeled 8) and 6 (labeled 64) stops, not 8.

Your .9 ND is the same as ND8 on the DVX100.
 
It sounds like a filter issue. I had the same problem using a schneider tru pol on a f900.
Sometimes filters just don't work same way through different cameras.
 
True nuetral density glass filters should not do this. There are cheap ND filters that have a color cast to them.
 
ND filters reduce the amount of light passing through the camera lens without changing the color of the scene.. ND's should have no effect on your color changes unless defective coating/glass has been used.. What brand filters?
My boys at the camera house want to know what you clean the filters with.. There are some cleaners that could leave a haze which might direct light at different angles into the lens. Scary, but true..

Have you mistaken your 4x4 pola for an ND? Check your filters.. Even on big budget films, mistakes can happen.. Check all your filters..

You did not answer the question about auto or manual white balance/exp.?

Let us know how it goes.. Good luck, and leave out the ND's for now!

- - Justin
 
My understanding is the same - NDs do not (should not) change the color.

We checked the filters many times and then performed a test looking at the wall with the bright highlight - slid the filter in and saw the color change occur - so it is the filter (and/or the interaction with the camera) causing it.

As for white balance we tried white balancing before and after inserting and it did not correct it.

Good news is the footage is usable and only someone clued in with notice. But it is a blatent and selective color change

Yep - we are leaving the filters out until i can triage this.
 
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