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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Red and the infraRED

Deanan said:
To quote Pancro: "Our ND filters are good in the near IR and out to about 1200 (nm) in the mid IR."
Click to expand...

I have access to a set of the Pancro mirrored ND's. Do you think these would be effective, or would they only cut "some" of the IR.

Dylan Macleod
Cinematographer
Toronto, Canada
www.dylanmacleod.com
 
Mike Prevette said:
Mick- A typical hot mirror or 486 does not cut sensitivity or leave any color cast. The exception to the color cast issue is for light entering at steep angles (ie the sides) the filter starts to effect the visible red spectrum thus leaving you with cyan vignetting as I've shown in earlier posts in this thread. I'm a little confused by your test, a filter for an "IR modified nikon" to me means it's passing all IR and no visible light. Am I understanding you right?
Click to expand...

Mike sorry, my bad; I was not clear; the filter I used was the filter that Lifepixel (the company that modifies SLR's to become infrared sensitive ) took out of my D100 to make it IR sensitive, so the filter I used is for blocking IR light and does that very well for the Red as well apparantly. The only thing that I tried to do was to see for myself how IR sensitive the Red was (after some magenta hues on heavily red saturated subjects) and what one can do about it, but luckily there are companies like Schneider that might provide us with good alternatives for solving the IR issue.
 
dmacleod said:
I have access to a set of the Pancro mirrored ND's. Do you think these would be effective, or would they only cut "some" of the IR.

Dylan Macleod
Cinematographer
Toronto, Canada
www.dylanmacleod.com
Click to expand...

I have not tested Pancro's with RED yet so I can't say for sure
and Pancro does not release spectral plots for their NDs.

However, silicon based sensors are sensitive to about 1200nm so
in theory they should work better than regular NDs and cut
IR and visible light similarly.
 
I'll call around Seattle tomorrow and see if anyone has any. Maybe I can setup a test.
 
It's good to see that you have been attentive to this problem from post #2 Deanan. Is there other Red employee's working feverishly on this big problem? People have complained about skew and other things but this IR problem that Mike has discovered and proved is there is for me by far the biggest issue with the camera today.

In the below post you mention that red is looking for a OLPF/IR filter that does a better job. When red does discover a filter that fixes this problem would you have a camera recall to retrofit in the new filter or would this be an pay for upgrade?

Deanan said:
It's not possible to simply swap out the OLPF/IR cut filter for only an IR filter as they are the same filter. It also has to be done in a clean room by RED. The spec for OLPF/IR is considerably different than the spec for a filter in front of the lens.

We are constantly evaluating new formulations of IR/OLPF filters to see if we can find one that's better than what we have. So far we haven't found one that's better but we will keep trying.

An additional filter in front of the IR/LP will affect FFD but it will also create more inter-reflections and possible degradation depending on the quality of the glass and the AR coatings on the filters.

I've seen 6x6 hot mirrors before but can't find the source at the moment.
Click to expand...
 
PG&O in Santa Ana, CA makes custom optics, and their "hot mirror" specs look like about what you want. I doubt they'd be interested in a one-off at any reasonable price, but maybe a larger order might become practical? No idea.

http://www.pgo.com/link_thin_film/hot_mirror.html

They mention having 1.75 mm and 3.30 mm thick hot mirrors as a stock item.
http://www.pgo.com/pdf/hrm.pdf

------------------------
In PG&O’s continuing effort to accommodate its customers, we offer numerous Glass & Thin Film Coated optical materials that can be either shipped from stock, or customized to your exact specifications and delivered within 48 hours.

Parts need to be one of the following shapes:

* Square
* Rectangle
* Circle

Sizes: .500” (12.50mm) thru 24.000” (609.00mm)
Dimensional tolerances:
For thicknesses ≤ .120” (3.00mm) the tolerance is ±.010” (0.25mm)
For thicknesses > .120” (3.00mm) the tolerance is ±.030” (0.76mm)
Edge Finish: scribed edge with a safety swipe
Surface Quality: 80/50 scratch/dig
$450. 00 minimum order (we will accept multiple items)

http://www.pgo.com/48_hour.html
 
Finner said:
but this IR problem that Mike has discovered and proved is there is for me by far the biggest issue with the camera today.
Click to expand...

I didn't know IR was causing it, but I've always been concerned about bright daylight performance. Hopefully IR filters are part of the solution. But really heavy ND's are hard to make perfect regardless. So the combo of those 2 problems is a little scary. It may be that 1.2, plus polarizer, plus IR filter is about as far as you can take it.

Film has the edge here. You can go buy 50 speed.
 
David (h20pixels)

Be careful here. They (the link) are using two opposed polarizers to create a "ND effect" which is similar on the surface but VERY different to how actual ND's work.

The Magenta shift they are experiencing is due to the lowish quality of their polarizing filters which can't completely block the visual spectrum (ie go black to our eyes) Later in the article he says he tries it on a IR specific camera and the filters had no effect.

Like I said before, a slight magenta shift is common when stacking ND's as no ND has perfect colormetry. It's also much easier to correct than the IR problem we are talking about here. It's a simple matter of subtracting 10pts magenta from the scene uniformly. The IR issue is far less uniform as some things reflect IR and some don't.

I want to make sure this thread stays as honest, and scientifically accurate as possible so people can find a clear solution to their issues in the future.
 
Mike Prevette said:
Be careful here. They (the link) are using two opposed polarizers to create a "ND effect" which is similar on the surface but VERY different to how actual ND's work.

The Magenta shift they are experiencing is due to the lowish quality of their polarizing filters...
Click to expand...

Wow. That is exactly where the color shift is coming from in their examples. Stacking cheap polas is how I used to achieve cool looking purple skies in my still photography.

I would take whatever else this rubbish article is saying with a big grain of salt. If they are making amateurish mistakes like this I wouldn't give much value to whatever they are saying!
 
Mike Prevette said:
I want to make sure this thread stays as honest, and scientifically accurate as possible so people can find a clear solution to their issues in the future.
Click to expand...

There's speculation all over this thread. The IR problem doesn't seem
to be huge problem(IMHO) from what I've seen. Just something that needs to be noted if you're using strong NDs. I'd like to hear more about the Pancro solution and if that works fine.

One thing to remember is what a great deal the camera is. Customers trying to strongarm red into fixing all the cameras out there is going to force the price up for all of us. Looking the gift horse in the mouth could lead us down a path that makes red less accessible.
 
Filter me

Filter me

Assuming that silicon based sensors like CMOS have issues with sensitivity to IR, I would think that one or more of the big filter companies will happily jump into this market.

I'd like a 4 x 5.65 for under $400 please. Where do I make my reservation? :detective2:
 
Ariana said:
There's speculation all over this thread. The IR problem doesn't seem to be huge problem(IMHO) from what I've seen. Just something that needs to be noted if you're using strong NDs. I'd like to hear more about the Pancro solution and if that works fine.
Click to expand...

I guess you don't find it a problem because you never have plans to shoot outside durring the day?
 
Finner said:
I guess you don't find it a problem because you never have plans to shoot outside durring the day?
Click to expand...

I haven't had any problems so far and that's shooting mostly with ND3/6. Obviously, if I need to go more I'll test the Pancros or the new Schniders mentioned. For everything else all the daylight shot look good so far.
 
Ariana said:
I haven't had any problems so far and that's shooting mostly with ND3/6. Obviously, if I need to go more I'll test the Pancros or the new Schniders mentioned. For everything else all the daylight shot look good so far.
Click to expand...

You must have very dark days where you live. Here with the native 320ASA sensor and a ND3 or ND6 the T-stop would be between T11 and T16 or higher. For the shooting I do those stops are not acceptable.
 
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