Built In IR Filter?

C

CaptainSKA

Active member
I noticed in another thread someone referred to the piece of glass in front of the F35's sensor as an IR filter. If this is true, does that mean that I do not need IR filtration in my NDs? Obviously it doesn't need a Hot Mirror like the RED cameras do, but does it need an IR filtration in the NDs?

Thanks,

Kevin
 
My NDs are currently all NDIRs, but I thought I'd see if they actually needed to be. Why do you say this camera needs it more than any other camera?
 
Generally speaking, cutting light with ND's that don't have IR cut (with any camera) reduces visible light only, not IR, and therefore reduces the light vs IR ratio. So there will be much higher IR contamination (magenta blacks usually become the issue)
As your ND's increase in strength, the ratio gets smaller and smaller, requiring increased IR filtration as you block more and more visible light.

Here's a nice diagram to visualise what happens with ND's:

IR_visible-light-ratio,-no-ND_309_464.jpgIR_visible-light-ratio,-with-ND_310_285.jpg

Here is a good read from Art Adams: http://provideocoalition.com/aadams/story/f35_ir_filter_shoot_out/
 
Good to have. If not, you'll spend a long time spinning your balls (pun intended) in Resolve and it still looks unnatural. Get up above 1.2ND w/o IR, you'll wonder what happened.
Most cameras suffer from this issue, but the newer Canon's seem to have figured it out…they must put IR into their internal ND's.

Tiffen's Hot Mirror is a good choice for someone who has a fortune already invested in ND (I think I have almost ever variation of ND and ND grads known to man) since it blocks the entire spectrum of IR and can be stacked in front of ND. If I had to do it over again, I'd get all HotMirror ND's, but have never seen them in grads.
 
You MUST NOT use a Hot Mirror with the F23/F35/F65 - it's pointless.

Use Tiffen IRNDs or (I think) Schneider Platinum IRNDs. Check the Art Adams article for the technical explanation.
 
JMtheDP said:
You MUST NOT use a Hot Mirror with the F23/F35/F65 - it's pointless.

Use Tiffen IRNDs or (I think) Schneider Platinum IRNDs. Check the Art Adams article for the technical explanation.
Click to expand...

Hot mirrors don't offer much (if any) benefit over the IR cut filter already in the camera, according to Art's study.
This page is a summary of his findings and offers a concise answer to the question at hand regarding the hot mirror vs. no hot mirror. I have hot mirror NDs, but I had them before I got the F35. I got a Tiffen T1 filter eventually.
 
Thought the Hot Mirror reflects all IR, so I'd like to hear a technical explanation of why, "for use with the F35 or the Genesis as that's a waste of money. Save that enormous expenditure for your cheaper cameras, like the RED."? Sounds like some elitist politics going on. I've had good success with it.
 
I believe, although don't quote me on it, the point is that the hot mirror is complete overkill for the F35, which already has one of the best built-in IR filters of all time. The Tiffen IRNDs are specifically made to be sympathetic to the filter already built-in, only affecting the portion of IR that the internal filter doesn't deal with.

It is my understanding that bit of IR it doesn't deal with is left there to give you natural looking reds and skintones under normal (non-ND) situations in tungsten light, when red is a vital component
 
I can neither confirm nor deny that, but it certainly sounds feasible. The newer Canon EOS Cinema cameras seem to have it figured-out. They do exceptionally well with no IR filtration.
 
There are lots of cameras which never had a problem with IR pollution, but a lot of them are cameras which couldn't really take advantage of the far-red information anyway, as their colour palette was so limited compared to the F23/F35/ALEXA/RED etc....

I think RED based their camera on a DSLR design (from an operational standpoint) and probably didn't really think of it much because its relatively uncommon to use NDs when shooting stills...
 
If you aren't a colorist, you will be sad if you don't use an IR solution on this camera. I've been able to pull some heavily polluted images back from hell, though, so it's not all too bad.

Still, I would prefer the base image not have the contamination, in most instances you just cannot pull it out of skin.
 
Hey guys, I have a few straight forward questions, I think. I wish I could just write Art Adams an email but I doubt that is possible.
These questions are based on field tests which I rely on more than what the manufacture tells me.
I know Tiffen IR ND filters CAN NOT be combined with regular ND's.
But now since we have the T 1/2 & T1, we can combine them. Right? But how much regular ND can be stacked or used and still have the T 1/2 or T1 cut the far red out?
Also does anyone have any experience stacking IRND's? I would think that stacking them should be fine considering the far red is removed based on the amount of ND in that filter?
[h=1][/h]
 
I think you should be fine stacking IRNDs - presuming they are the same make - and I think the point of the T 1/2 and T1 are that they just cut out all the relevant red, then if your NDs are behind it its kinda irrelevant.
 
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