Blackmagic Forum

Hi.

I wonder if bmc needs any ir filtering outside?

Was playing today with alexa and there it was advisable to use nd with ir back red filtering.

Does this apply to bmc also as digital sensors are mostly sensitive to ir or
is this already handeled inside camera?

And if so does this happen only with nd or do you hafe to filter ir all the time when filming outside in natural light?

I remember reading that the BMCC has a IR filter built in which sits atop the sensor. I'm not sure where I got that from mind you.

As found in a BMD FAQ published by an Australian retailer:

(page 3)
Q: How do I clean the sensor?
A:The sensor is sealed behind a glass IR filter so you will not be able to get to it. So you only need to limit your cleaning to the glass filter.

http://newmagic.com.au/support/Files/Bl ... ra_FAQ.pdf

My understanding is that the camera, and ones like it, will still require an IR filter if you're using more than 1.2ND. Hopefully there are others on this forum that can confirm this.

Because of the way ND filters work, IR 'pollution' or 'color distortion' increases as you add ND, especially at about 2 stops or more. So you have to add external IR filters to keep it clean. You can find discussion of this on RedUser, for example. It is not because of a problem with the IR filter on the camera, it is because the ND filters are not perfect, and cause the problem. They do not filter the IR in addition to the visible light.

What about "high end" ND filters. Do any of them comoensate?

You'll see IR contamination when you use an ND heavier than a 1.2 (4 stops). You can jusssst start to see it at an ND 9 but it's barely there. As you go heavier it will get worse.

I've tested the T1's and the PLatinum IRND's and they both seem to work well, as does a regular IR in front of non IR ND filters.


jb

Edit: John already mentioned the IRND so I don't know why I said anything.

What do we know about the new Tiffen IRND + Glimmer Glass filters? They look very nice and I hear good things about Tiffen full spectrum IRND with Alexa...maybe they behave the same with the BMCC?

If one had to suggest any particular set of IRND filters that would otherwise be a great fit for the BMCC (for shooting sunny 16 and under situations at ISO800 at a respectably shallow DOF), I'm all ears

Since there is already a IR filter in the camera, it doesn't make much sense to add a second one.
What you want is a NEAR-IR filter like the Heliopan BLF 1x, LW -0 that starts to cut down at 780nm of wavelength.

Did a little test.

1. BMC stepped down,
2. Heliopan Vari ND @ max setting (ugh),
3. Heliopan VariND @ max setting + Heliopan BLF 1x, LW -0 on top of it.

Shot on ProRes with a redhead light.

Weren't variable ND's generally discouraged though because they are far worse than normal ND filters?

Frank what did you conclude?

I have ? mark where it should be image i believe.

So, is IR filter a must to have thing when using a ND filter more than 0.9?

probably you do not have to use it but question is what happens to your images.

it seems to me to be advisable to use them.

Abelcine has a comparison of several cameras, including BMCC, with different IR filters. The BMCC has very little IR filtering built in.

Look for: Abelcine Expo Highlight: Filters for digital cinema

Cheers.

Nick Bedford wrote:Weren't variable ND's generally discouraged though because they are far worse than normal ND filters?

If you have a Heliopan or Genus Eclipse, you are golden. Both work just fine for me, even on longer glass.

Genus seems nice

Frank Glencairn wrote:

Nick Bedford wrote:Weren't variable ND's generally discouraged though because they are far worse than normal ND filters?

If you have a Heliopan or Genus Eclipse, you are golden. Both work just fine for me, even on longer glass.

Hi Frank,
you advice to always use the Heliopan BLF 1x, LW -0 put on it? i have the slim vs of heliopan, so I can't I suppose. is possible to mount back...it's correct or I need the screwed version?
thanks for your info

andrea

Frank Glencairn wrote:

Nick Bedford wrote:Weren't variable ND's generally discouraged though because they are far worse than normal ND filters?

If you have a Heliopan or Genus Eclipse, you are golden. Both work just fine for me, even on longer glass.

I have a vari nd from cheap brand called citiwide.. Interestingly, it was superb with my 7D in case of IR pollution, I didn't experienced any excessive problem with it...

On the topic of IR, and so I don't have to buy a bunch of NDs for each lens or deal with step-up/down rings, are these any good? I'm assuming they are, but don't want to purchase without double-checking with you guys:

http://www.bhphotovideo.com/c/search?at ... +filter+IR


I bought the Lightcraft Fader ND and wasted my money b/c I found out it's kinda crap. Will these filters reduce any sharpness or pollute my image? I have a mattebox that holds 4x4 filters.

PaulDelVecchio wrote:On the topic of IR, and so I don't have to buy a bunch of NDs for each lens or deal with step-up/down rings, are these any good? I'm assuming they are, but don't want to purchase without double-checking with you guys:

http://www.bhphotovideo.com/c/search?at ... +filter+IR


I bought the Lightcraft Fader ND and wasted my money b/c I found out it's kinda crap. Will these filters reduce any sharpness or pollute my image? I have a mattebox that holds 4x4 filters.

I've used the 4x5.65" versions of the 0.3, 0.6, 0.9 and 1.2 Schneider Platinum IRND and they worked fine on a RED Epic with CP.2's on a feature I was shooting at locations in LA and Texas which each exterior has its own "feel." In the middle of the day LA is cool and breezy in October at 90 degrees C, central and south Texas is balmy and humid at 80 degrees C three days later. The filters handled fine and did their job quite well: the only light loss was the loss I sought for using ND. I stacked two IRND quite a few times and didn't notice any significant loss of skin tone, though I did notice a slight increase in green, but with one node it corrected just fine. I hadn't had time, nor had they budgeted, for tests of any kind so this was something we had to find out with the rushes. But Redcode cut through it fine, so I suspect the BMCC will do equally as well. I like them. If you can afford the 1.2, the 0.6 and 0.3 you should be fine for most everything.

Jason R. Johnston wrote:

PaulDelVecchio wrote:On the topic of IR, and so I don't have to buy a bunch of NDs for each lens or deal with step-up/down rings, are these any good? I'm assuming they are, but don't want to purchase without double-checking with you guys:

http://www.bhphotovideo.com/c/search?at ... +filter+IR


I bought the Lightcraft Fader ND and wasted my money b/c I found out it's kinda crap. Will these filters reduce any sharpness or pollute my image? I have a mattebox that holds 4x4 filters.

I've used the 4x5.65" versions of the 0.3, 0.6, 0.9 and 1.2 Schneider Platinum IRND and they worked fine on a RED Epic with CP.2's on a feature I was shooting at locations in LA and Texas which each exterior has its own "feel." In the middle of the day LA is cool and breezy in October at 90 degrees C, central and south Texas is balmy and humid at 80 degrees C three days later. The filters handled fine and did their job quite well: the only light loss was the loss I sought for using ND. I stacked two IRND quite a few times and didn't notice any significant loss of skin tone, though I did notice a slight increase in green, but with one node it corrected just fine. I hadn't had time, nor had they budgeted, for tests of any kind so this was something we had to find out with the rushes. But Redcode cut through it fine, so I suspect the BMCC will do equally as well. I like them. If you can afford the 1.2, the 0.6 and 0.3 you should be fine for most everything.

Cool, thanks for the info. I think I might go for these rather than a Heliopan ND because I'd rather not buy multiple ND filters for each lens. I guess I could probably use step up rings and such, but that could get annoying every lens switch. I'd rather just pull a lens off and swap it out with another and not waste time screwing and unscrewing filters. I supposed the 4 x 5.65" ones would be better if I wanted to really future proof my investment so I'd have to get a new mattebox, as the one I have only holds 4x4 filters. Still though, I like using a mattebox instead of screw on filters. Much faster.

Screw-on filters are for stills photography. When you hit serious cinematography you'll find PL mount lenses don't have filter threads! Big heavy matte box with 3 rotating filter stages, an eyebrow and wings, is where it's at. Gimme Schneider Trucut IR cutter in front with a Tiffen linear polarizer and graduated ND and I'm in heaven.

it really depends what you are after. really small hand held shoot then you may not want to use matte box.

Margus Voll wrote:it really depends what you are after. really small hand held shoot then you may not want to use matte box.

True. But for run-and-gun, I'd rather use a Panasonic HPX170. The BMCC seems like more of a feature film/TV episodic/advertisement/controlled documentary camera. If I'm moving fast I'd rather have a camera with everything built in, like ND.

Jason R. Johnston wrote:

Margus Voll wrote:it really depends what you are after. really small hand held shoot then you may not want to use matte box.

True. But for run-and-gun, I'd rather use a Panasonic HPX170. The BMCC seems like more of a feature film/TV episodic/advertisement/controlled documentary camera. If I'm moving fast I'd rather have a camera with everything built in, like ND.

The mattebox I have is small so I can use all this stuff in run and gun scenarios, although, yes, something like an HPX170 would be better. I have a 4x4 mattebox. I use my stuff for films and while I do like to keep my rig small, I find that my rig is small enough for handheld film work, even with a Marshall 7" monitor mounted on it.