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Filed under: Cameras •Production •

Schneider IR Filter Tests

Art Adams with the 486 filter on a RED ONE

Last week, Art Adams, Tim Blackmore, Ted Allen, and I tested the Schneider 486 UV/IR cut filter on a RED ONE and on a Sony PMW-EX1. Tim wore his famous “doesn’t look anything like that in real life” “black” shirt, and we lit him with IR-rich incandescent sources.

Tim Blackmore in the hot seat at Videofax.

Tim’s shirt appears black to the eye, as it does to the Nikon D300 DSLR:

Tim and friends as seen by the Nikon D300.

But his shirt uses a fabric or dye that reacts strongly to IR and/or UV, reflecting a lot of energy back to the camera that’s outside of the human eye’s passband, but well within the limits of what a CCD or CMOS sensor can see. We have noticed that many cameras see that shirt as a reddish-brown, especially when ND filters are used (as they were in the outdoor shots in the three-camera comparison, to get all the lenses opened to T2.8). And while the RED actually does a better job than other cameras we’ve aimed at that shirt, even the RED’s rendition starts drifting when heavy ND filtration is used.

Art obtained a Schneider 486 UV/IR Cut filter from Schneider’s booth at NAB, and we   showed up at Videofax to try it out on both the RED and on the Sony PMW-EX1.

Our first surprise, upon setting up, was seeing that the RED saw Tim’s shirt as a shade of blue, neither neutral black nor reddish-purple. Furthermore, the 720p monitoring output seemed to accentuate the green-magenta axis excessively, more so than the onboard LCD did. Quick off-the-monitor shots from both the RED and a Varicam that Videofax’s Jim Rolin set up for us confirmed that (a) the RED saw Tim’s shirt as blue while the Varicam (like other video cameras) saw it as being reddish-purple, and (b) the RED’s monitor output exaggerated the green-magenta axis.

RED’s monitor output: exaggerated green & magenta; blue shirt.

Varicam’s rendition: less color exaggeration, red/purple/brown shirt.

We shot Tim with RED and a 28mm Ultra Prime, with and without the 486 filter:

Tim without any filtration, RED.

Tim with the 486 filter, RED.

In my frame grabs, I’ve color-corrected both shots to match on the grayscales; seen uncorrected, the 486 filter imparts a slight green/cyan cast (as you might expect, since its visible reflectance is red/orange).

With no NDs in place, the 486 had only a minimal impact on RED’s colors; it pulled a slight bit of purple from Tim’s shirt, but the shirt still reads as blue.

Next: the PMW-EX1; RED with NDs; wide-angle lensing.

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Hi Adam-

Great article, as usual! The ND on the outdoors shots of Tim was an ND .90, in addition to a polarizer, which comes out to about 4 2/3 stops.

More to come when I stop shooting so much.

-Art

Posted by Art Adams  on  05/02  at  06:23 AM

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Hi Adam,
Thanks for this heads-up. I’m using the 486 with my EX1, and while indeed vastly improving the colour rendition in warm (tungsten / incandescent) lighting, it also adds the green cast to the image extremities (starting with just slight vignetting, ending with greenish areas along the left/right edges at full wide). It’s much more pronounced that what you’ve mentioned!

In other lighting conditions (like with pure sunlight, or with LED lamps) the negative effects are negligible, if any at all.

I’ve posted a couple of grabs illustrating this on the EX1 DVINFO forum.

Cheers, and please never stop feeding us with your invaluable insights!

Piotr

Posted by .(JavaScript must be enabled to view this email address)  on  05/02  at  07:16 AM

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Damn I missed another awesome test!!!!

Posted by .(JavaScript must be enabled to view this email address)  on  05/02  at  07:26 AM

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Adam,
Thanks again for another very informative article. There seems to be some tradeoffs under tungsten / incandescent conditions, but it apparently works great it daylight balanced lighting.

Posted by .(JavaScript must be enabled to view this email address)  on  05/02  at  08:02 AM

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Nice test.
How about doing a test outdoors in full daylight? Maybe include some foliage, sky and water.

Posted by .(JavaScript must be enabled to view this email address)  on  05/02  at  10:21 PM

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Read the entire article. If you’ll turn to page two you’ll see full daylight with foliage. Water will have to wait.

Posted by Art Adams  on  05/02  at  10:25 PM

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