Blackmagic Forum

Hi,

I shot several scenes with cheap tungsten spotlights. Since its for a metal band, all wear black t-shirts.
But, they look red, or better brown. (whereas guitars and leather stays black, so its not a colorgrading issue).

Since the BMPCC are very sensitiv to IR and tungsten light has a lot of IR and some black clothing are brighter under IR light (those which are colored red before black) I think IR filter is necessary for shooting with tungsten light.

Can someone confirm this?
Is this a problem only with 100W to 400W spots from DIY market or generally, even with 1kW ARRI etc.?

I mean IR stop filter of course. Not IR filter for IR-photographie.
Thomas

I've never needed an IR filter under tungsten light-- but perhaps your heads/bulbs are putting out a lot of IR for some reason.
Something like a hot mirror filter may help- but I find it does rather not nice thing to skin-tones.

The BM cameras are much more sensitive to IR light than other cameras. In most cases it's only noticeable when you use ND over 0.9 but it can be an issue in cases where there is no ND used at all.

A lot of users are using the Hoya IR Cut filer. I have a 77mm in my bag and use it most of the time.

Amazone US: http://amzn.to/1dFK3JC
Amazon UK: http://amzn.to/1jXaSuq

Yes, that's totally possible. I've had a similar experience when filming night scenes only lit by torch-flames and a bonfire: lots of redish-brown casts on some "black" materials, yet not on others - a nightmare to grade. Haven't had that that problem again since i added a cheap IR-filter to my backpack.

For the footage you have already shot you could try CaptainHook's "IR CUTTER LUT".

Near the bottom of the page:
http://www.captainhook.co.nz/blackmagic ... amera-lut/

Even a RED Scarlet starts to show some IR pollution from ND 0.6, and the BMPCC is even worse. It's quite possible it shows with no ND at all under critical sources.

I can affirm the above since I've just been editing a project from a few months back, shot all indoors with no NDs and using various lenses (c-mount + Voigtlander MFT + Nikkors). I do have IR pollution all over the (raw) footage. Maybe because part of it was shot in a high rise building on an upper floor in daylight, and the other part in available tungsten light. In any case, the difference is really striking with the footage that I shot lately always having IR cut filters in front of the lens.

Hook's anti-IR pollution powergrade helped with that footage (when dialing down the Node/LUT strength to 25% though). But as collateral damage, it sucks a lot of color out of the image and makes it look more artificial.

So better avoid this issue while shooting.

The BMCC definitely loves red and needs a nice IR cutter even without ND, especially in a scenario like the OP's. It's easier to deal with in raw, but, it's acceptably dealt with in ProRes if it's not too obvious. Next time, you know what to do now. I recommend Tiffen full spectrum IRND or just a nice Schneider 680 tru-cut. I'm not a fan of hot mirrors, but that's a personal preference.

Jason R. Johnston wrote:The BMCC definitely loves red and needs a nice IR cutter even without ND

THIS

Anyone test the 486M with the Sigma 18-35, how green is it? I was going to get the Hoya, but my friend is selling the B+W for cheap.

If you were to suggest a high quality circular IR filter, what brand would you suggest?

I use 82mm ND/CPL filters I already own so being able to stick the IR filter on that would be good.

Nick Bedford wrote:If you were to suggest a high quality circular IR filter, what brand would you suggest?

I use 82mm ND/CPL filters I already own so being able to stick the IR filter on that would be good.

The Hoya IR Cut linked to above works well. They also do an 82mm.

Does the Hoya have threads on both sides & does it matter if you put it before ND filter (got a 82mm Genus Eclipse & the external filter thread is larger than 82mm, so trying to avoid yet another step ring).

thanks

To give an update, to anyone who wants to buy the B+W IR cut to save money, I don't recommend it for shorter than 50mm. There is definitely a greenish hue, I would stick with the Hoya.

Stu Lyall wrote:Does the Hoya have threads on both sides & does it matter if you put it before ND filter (got a 82mm Genus Eclipse & the external filter thread is larger than 82mm, so trying to avoid yet another step ring).

Yes, threads on both sides.
From my tests it makes no difference which side of the variable ND you place the Hoya IR Cut. The result is the same on both sides.

If it was a Hot Mirror filter, which it's not, then you would need to place it on the outer most point of your light path as the Hot Mirror filters reflect and would cause ghosting and other odd image anomalies.

adamroberts wrote:

Stu Lyall wrote:Does the Hoya have threads on both sides & does it matter if you put it before ND filter (got a 82mm Genus Eclipse & the external filter thread is larger than 82mm, so trying to avoid yet another step ring).

Yes, threads on both sides.
From my tests it makes no difference which side of the variable ND you place the Hoya IR Cut. The result is the same on both sides.

If it was a Hot Mirror filter, which it's not, then you would need to place it on the outer most point of your light path as the Hot Mirror filters reflect and would cause ghosting and other odd image anomalies.

Thanks, really need to get one as IR pollution has really started to become a problem & you anticipated my next question about Hot Mirrors!