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Basic

Intensity

Exposure

Specifies the exposure of the area light as a power of 2. Increasing the exposure by 1 will double the energy emitted by the light source. A value of 0 produces an intensity of 1 at the source, -1 produces 0.5. Real world lighting has high energies and typical exposures are low values while you may have to type a really large number for equivalent  Intensity . This is also comfortable to artists familiar with photographic measurements. The intensity is reset to 1.0 so the result starts darker than above because of the physical falloff of the light.

Color

The color of the emitted light.

Enable Temperature

Turns color temperature on or off.

Color Temperature

Refine

Emission Focus

Off-axis cosine power exponent to shape the emission. This controls the spread of the light. Higher numbers will start focusing the light towards the center and thus narrowing the light spread.

Emission Focus Tint

Off-axis light color tint. This tints the emission in the falloff region starting from the off-angle direction of the light towards the center. By default, the tint color is black (none). In addition to tinting, values greater than white will also increase the intensity of the falloff region. Notice when using White the emission focus nearly appears to be off.

Specular Amount

Amount of specular light that is emitted. This is a non-physical control. You could use a light with  Specular Amount  0.0 to act purely as a source of diffuse light for your scene objects and avoid adding highlights. This scene has subtle reflections but you can notice the light disappears from the reflection in the chrome ball far right.

Diffuse Amount

Amount of diffuse light that is emitted. This is a non-physical control. You could use a light with  Diffuse Amount  0.0 to act purely as a source of highlights for your scene objects.

Intensity Near Dist

Near distance between the point being illuminated and the light at which the sample doesn't get brighter. This may help you avoid hot spots and sampling issues where a light is near a surface. These values are based on your scene scale/distance so this is just an example.

Cone Angle

Angle of the virtual flaps on the light to turn it into a spot light. This does not affect IES Profiles (should you be using one).

Cone Softness

Softness of the cut-off of the Cone Angle. The regular range is from 0 (hard cut-off) to 1 (smooth transition), but it can be set higher than 1 for additional gradation. Above in the Cone Angle you notice how hard the edges look, this parameter improves that result to be more pleasing.

Light Profile

IES Profile

Name of an IES light profile. Below makes use of three different IES profiles and some dark mood lighting.

Profile Range

Shadows

Enable Shadows

Enable raytraced shadows.

Shadow Color

The color of the shadows cast by emitted light.

Shadow Max Distance

The maximum distance of the shadow starting from the position of the point being shaded. -1.0 is unset which will use the distance between the point being shaded and the point on the light. You may use this control to artificially reduce the distance shadows are cast. This may also increase render speed by not calculating shadows outside this distance. Here it's used to remove the shadow off the back wall from the flashbulb effect of the light.

Shadow Falloff

The distance from the light at which shadow falloff begins. -1.0 turns off shadow falloff. This is used along with  Shadow Max Distance  to create a false fade for shadows that are reduced or cut off by the  Shadow Max Distance  parameter. Below is an example with both parameters being used and the falloff is increased. Note this parameter may impact performance on complex lighting setups.

Shadow Falloff Gamma

The gamma of the shadow strength in the falloff zone. This requires the use of  Shadow Max Distance  and  Shadow Falloff .

Trace Subset

Set of geometry to consider for traced shadow intersection. If this is not specified, all geometry are considered for traced shadow intersection.

Don't Trace Subset

Set of geometry to ignore for traced shadow intersection. If this is not specified, all geometry is used for traced shadow intersection.

Advanced

Normalize

When normalize is enabled, the amount of light contributed to the scene will not change as you scale the light source. This makes it easier to adjust highlight size without changing scene lighting.

Trace Light Paths

Enable light and photon tracing from this light. This value enforces a physically-based light and as a side-effect disables the above  Shadows  controls. Users may use this feature to selectively decide which lights emit photons when using the PxrVCM or PxrUPBP Integrators.

Thin Shadow

Enable thin shadow and disable refraction caustics for this light. This parameter will ignored if  Trace Light Paths  is enabled. This is a non-physical control that creates "fake" colored shadows for transmissive objects without needing to generate photons for caustics. Notice we lose the colored shadows and interior colored reflection choosing Off, but we gain some render speed instead.

Light Samples

Specifies an override of the number of light samples to be taken for this light source. If set to something other than zero, it will override the sampling performed by the integrator. It's recommended to leave this at the default unless you experience unsolvable noise from the light.

Light Group

Specify the light group name used for light group LPEs. This is useful to generate per-light AOVs for later adjustment in compositing.