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View Full Version : IR Filter VS IR OLPF



Carey Lee Coffey
11-12-2014, 08:59 AM
I am just now delving into IR cinematography.

Simple and to the point, can I use this Hoya screw on filter (http://www.bhphotovideo.com/c/product/122481-REG/Hoya_B77RM72_77mm_RM72_Infrared_Glass.html) on a Dragon and achieve the same results I would get from the upcoming (soon to be released) interchangeable IR OLPF and/or from using an IR modified Dragon?

Here's the look I'm trying to achieve:

https://vimeo.com/66698520

Thanks for your input!

Burke Doeren
11-12-2014, 11:37 AM
From what I can tell, the Dragon's OLPFs are designed to cut almost all IR, so if you add this Hoya filter you'd cut out almost all visible light. You would be left with a tiny amount of near-IR light coming through, but I don't think it would be the same experience as that Movi RED Epic IR Test.

That being said, I haven't tested it. Might be worth a shot, especially if you can shoot ultra fast primes around T/1.4 in broad daylight.

John Marchant
11-12-2014, 11:46 AM
Nope, you need this AND an IR pass OLPF module.

Carey Lee Coffey
11-12-2014, 03:26 PM
Nope, you need this AND an IR pass OLPF module.

Can you elaborate John? What is an IR pass OLPF module? Again, just getting into IR cinematography and I am getting many conflicting opinions from many different sources.

Thanks!

John Marchant
11-12-2014, 03:32 PM
The OLPF is a package of filtration with many purposes - it diffuses the image to remove aliasing, cuts internal reflection, and as standard works to cut unwanted infrared light, in order to create images that tally with human perception.

The CMOS sensor itself is strongly sensitive to IR however. If we replace the OLPF with a version which does not cut IR, we see the whole spectrum that the sensor responds to. That means generally an overwhelmingly IR influenced image, with false and unexpected colour response. Further to that we can then use front-of-lens filtration to decide which light frequencies we'll work with.

I will shortly be making available for Dragon a full spectrum, zero-OLPF filter - to work with the interchangeable system. Red themselves may have in the works an IR specific version with the standard OLPF functionality. My design was created specifically for the highest resolution monochrome IR imagery, but its an interesting piece of gear with which to experiment on any Dragon.

I've shot a lot of IR now, and supported a number of high end wildlife shoots where its use was essential, so drop me a PM or email to discuss more if you like.

Asif Limbada
11-12-2014, 03:59 PM
this is good news.

Carey Lee Coffey
11-12-2014, 05:16 PM
Okay, I think I'm getting the gist of it.

I read this article (http://www.red.com/learn/red-101/infrared-cinema) on Red.com that gets into some interesting detail.

From the article:

"However, many hobbyists still create images with the remaining IR and UV light by using lens filters that block visible light. This has the advantage of not needing to modify the camera and void a warranty, but also requires prohibitively long exposures, so the approach is limited to still photographs and time lapse sequences. True infrared motion capture requires specially-modifying the camera sensor to unlock its full spectral potential."

Philip Jarmain
10-26-2015, 08:45 PM
I just received the Color IR Pass OLPF for my RED Dragon. I have installed it and tested it and thus far the black and white images are a bit muddy. What filter do you recommend I use in my matte box in addition with the IR Pass OLPF to get really high contrast black and white landscapes and architectural imagery with dark skies? Do you use a red filter like you would have with infrared film?

Philip

John Marchant
10-27-2015, 01:17 AM
You really need to use a deep red, or better yet a 720nm IR filter in front of the lens for what you describe. Can be easily found in screw fit, but harder as drop ins for your mattebox

I sell an IR spectrum only OLPF for just this reason :)

This will clean up the muddiness, but you should still expect a relatively low contrast image that requires a push of contrast curve to get you to the final look.

Arvind Mattadeen
03-23-2016, 01:27 PM
Hello everyone, very resourceful topic here! thanks for all the info John! really helped a lot! Anyone can guide through the process of white balancing and achieving the nice IR look? thanks