Barn doors are opaque moving panels attached to the sides of a light's opening. They are typically used in theatrical and film lighting for additional control over the shape of the light beam. This tutorial shows you how to use the Barndoor light filter and demonstrates various settings.

The Barndoor light filter introduces four barn door flaps. Each barn door flap has three parameters. The first two parameters position the two ends of the flap across the face of the light. The third parameter (Edge) controls the softness of the edge. This light filter can only be used with spot lights.

The following steps explain in more detail how to use barndoors.

• Create a Spot Light and a polygon plane. Point the Spot Light at the plane. Increase the Cone angle so that you can see the effect of the light.

• In the Material Manager, create a barndoor filter - Create> Arnold> Light filter> barndoor. Drag and drop it onto Light filters in the Details tab of the Arnold spotlight. Increase the Exposure to around 3.

_{Drag n drop barndoor onto Light filters}

• Increase the Top Left value to 0.2. You should notice that the Top flap of the barn door is now clipping the effect of the spot light.

_{Top left barndoor}

• Increase the Top Right to 0.2 to match the Top Left value. Notice that the barn door effect is more prominent. A value of 1.0 for both Top Left and Right would completely obscure the spotlight, and we would not see any visible light effect.

_{Top right barndoor}

• Now that we are happy with the position of the Top flap, let us increase the Top Edge slightly to 0.05. Notice how it softens the effect of the top barn door. Now we can repeat this effect for the Bottom flap.

_{Top edge barndoor}

• The bottom values, however, start from 1.0. To position them equally to the top flap reduce the Bottom Left and Bottom Right values to 0.8. Use the same value that we used for the Bottom Edge, that we used for the Top Edge 0.05.

_{Bottom barndoor}

• We now want to square off the Right edge of our spotlight. Repeat the above steps for the right barn door at the bottom.

_{Right barndoor}

• We can control how much light appears on the left side of the screen using the left barn door. Increase the Left Top and Bottom values to around 0.1. To pull the light in, even more, we could increase these values even further. However, we do not want a hard edge. Instead, we can increase the Left Edge to 0.1. This has the effect of gently graduating the light as it falls off.

_{Left Barndoor Edge}

That concludes this short and simple tutorial on how to use the Barndoor light filter.