A filter to map almost black to 0?

[0x80]

Hi,

I'm working with some footage which has white subjects against a black background. I'm using a second layer with a solid color and multiply to color these objects. The problem is the background color is not entirely 0, so the color gets mixed into that a little as well. I would like to use a filter to map almost zero values to absolute 0.

I found the threshold effect but its output seems to be binary. I need the lighter shades of grey and white to stay unaffected. How can I best achieve this?

[Sadler]

I can get a reasonable result using Automask, Brightness & Contrast and Levels effects all independently within Resolume. If you're applying a flat colour why not save a layer and use Add Subtract. Of course all this depends on the nature of your footage and whatever you're trying to achieve. You might be better off luma keying your footage before Resolume.

[0x80]

Ah yes I need a luma/chroma key. Forgive me for the noob description =)

I can't adjust contrast or levels since I need to keep the lighter colors intact. I found luma key as a layer blend mode but not an effect, but I figured it out. The v opacity slider adjusts the threshold. I'd rather apply it to the clips directly I think but maybe I should then pre-process the movies in fcp or something.

[Joris]

When you tweak the parameters on the Levels effect, you can pull down the lows only and keep the mids and highs intact. Of course you are always going to lose some dynamic range.

For a quick luma key effect, look at Auto Mask.

[0x80]

The levels and auto mask are exactly what I needed thanks!

One thing I don't quite understand is how multiplying with a solid color works. If you have a solid color on the top layer the color also affects the black when the layer opacity value is above 0.5. Why is that? Just curious. I would expect that even with opacity 1 the solid color is still multiplied by 0 in the black areas?

[Joris]

If the solid is on the top layer, it is blended with the layers underneath based on the blend mode chosen for that layer. Since you are expecting multiplication, I assume you are using the Multiply blend mode.

Multiply works that at 100%, only the layer is visible, at 0% the layers underneath are visible. No blending happens on these extremes. At any value in between these extremes, the layer is multiplied with the layers underneath. At 0.5, the multiplication happens exactly as you would expect. Moving the fader up from 0.5 will gradually fade in more of the layer and multiply less. Moving the fader down also multiplies less, but gradually shows more of the layers underneath.

I hope that makes sense.

Btw, for this simple colorizing of black and white footage, take a look at the colorize and / or tint effects.

[0x80]

Thanks Joris, I think I get how it works.

The colorize effect is much more convenient for what I'm trying to achieve since it doesn't require and extra layer. Wonderful