How to get rid of light reflections on wall?

February 24, 2010

Hi there,

Has anyone got any smart advice on how to get rid of these reflections on the wall behind the man with the torch?

http://www.youtube.com/user/PoisonedLightChannel#p/a

In the first half of the clip you can see the problem. In the second half you can see my unsuccessful attempts at defeating this problem in Photoshop by exporting the clip as layers and then working on each layer individually painting out the reflections. Before re importing the clip back into Final Cut Pro.

The problem seems to be that each frame looks good when viewed individually but viewed as a sequence the repainted frames are just as distracting as the original problem that I was setting out to solve! What should I be doing.

Does anyone have an idea. I have Final Cut Pro, Photoshop, Motion - It it possible using this software to cure this problem?

Thanks in advance.

Satsuki Murashige · February 24, 2010

Sorry, but what do you mean by "reflections"? Are you talking about the lens flare? I think you're doing the only thing you can do, paint it out frame by frame. You just need a way to maintain consistent density from one frame to the next. Possibly putting all the frames into one Photoshop file, but in layers. Then toggling the opacity back and forth to check. I'm sure there's a more clever way to do this, but I don't know what that would be.

The flare is really not so bad though - at least it's motivated by the flashlight. I would just live with it if possible.

Brian Dzyak · February 24, 2010

Those are reflections. It's a flare caused by direct light being refracted through the various elements in the lens. Some expensive professional (read: expensive) lenses help to reduce flares, but whenever that kind of direct light enters the front element of the lens, you'll get a flare and there's not much you can do about it.

One way to reduce the flare is to soften the light coming from the flashlight (torch). The way the shot looks now, the light level is brighter than it truly needs to be to sell the idea that the character is holding atorch and shining a light out into the darkness. Try placing a small circle of Neutral Density gel over the torch's front lens to reduce the amount of light it shines. You could also try to place a bit of diffusion material over it too.

The only reason you might need a high intensity light in a shot like this would be if you wanted to see a beam of light, in which case you'd create "fog" so that the light had something to shine against. You'd also be able to enhance this look by using Xenon flashlights, though typically, they need to be powered externally, so your Actor would carry the unit and the cable would be hidden up his sleeve and would trail behind him as he walked.

As far as fixing a flare in post, as you've discovered, there's not much you can do effectively.

Kai Hsieh · February 27, 2010

He's talking about the wall with the bricks behind the guy beside the window. You can see a slight reflection from the light, and in the attempts to remove it, it "sparkles."

Thomas Tamura · February 27, 2010

Those reflections on the wall are specular highlights. A post solution may be to generate a luma-matte then slip the wall behind it to eliminate the problem area. Painting it out wasn't a bad idea, but i can see why you're not happy with it. If you use Apple's Shake, or similar node based compositor, there ought to be a 'clamp' or 'compress' operator that you can use to isolate only the pixels above a certain value. A good old Luma-key ought to do the same thing. Ounce you have your holes cut it is just a matter of putting something behind that will match the wall -- or you may be able to use the wall its self.

Basically the this is caused when you reach a complementary angle to light source. In your clip it's worse in the middle, and as you mover more perpendicular to the building the effect is decreased. To avoid on location, careful where you put your lights, use flags, maybe dulling spray. Those are just suggestions, I'm sure someone on here will have better solutions than I.

Chris Millar · February 27, 2010

As has been stated ITS A FLARE

Internal reflection - sure its 'on the wall' but only in the footage not in the original scene...

Calling them reflections or specular highlights (although not incorrect in some sense) just serves to confuse. The post solutions are valid whatever the cause, but if you are going to reshoot the scene the distinction much be made clear.

Jim Hyslop · March 1, 2010

As has been stated ITS A FLARE

Well, you're right that there is a lens flare, but that's not what the OP was asking about.

Here's a frame grab:

The lens flare is on top of the actor's face. The reflections the OP is asking about are the specular highlights on the brick wall camera right. They don't start until about 5 seconds into the clip.

--

Jim

Chris Millar · March 1, 2010

ha ha

oh poop !

whoops!

but, there's still something in that the flashlight flare is so distracting I didn't see the actual issue ... :lol:

Will Earl · March 1, 2010

The way to deal with the specular reflections on the wall would be to paint up the fix on key frames so you have a clean patch, then track the clean patch so it moves with the wall and you don't get variance between frames (you may need to paint up multiple clean patches to deal with the flare passing in front of that part of the wall). Depending on how much noise is in your image you'll also have to denoise the plate first before painting the clean patch and then renoising it after you've tracked the clean patch in so it matches the rest of the scene.