# Difference between the scale and the size of a light in cycles?

To adjust the shape of area light in cycles, there is the Scale, or there is size in the light properties.

What is the best way?

• As far as I can tell, there seems to be no visible difference. Whatever works best for you. – gandalf3 Aug 26 '13 at 19:51
• I think since the object of the light does not carry any significant information for rendering (except position and orientation of course!), changing the scale doesn't have any impact. Adjusting the size will alter the light data object though, which will transfer its attributes to the renderer. – LiMuBei Aug 27 '13 at 14:36
• @LiMuBei changing the scale (S in 3D view) does impact the render, I just tested it. – gandalf3 Aug 27 '13 at 18:58

My observation from Blender 2.68:

Changing the size from the properties also changes the size in the 3D viewport.
Changing the scale in the 3D viewport does not change the scale in the properties.

The rendered result is the same in both cases. The only difference is in how you see the light in the 3D viewport.

Conclusion:
Either use one or the other, but don't mix. If you mix, the actual size of the light is different from the one you see in the 3D viewport. Though it will not crash anything, it may become confusing.

• Good answer. There's one thing I would like to add: with scale you can make the light rectangular instead of square. – jasperge Aug 27 '13 at 14:56
• @jasperge you can make it rectangular in the properties too, change the dropdown above the Size parameter to Rectangle. BTW, from what I saw, scaling in the 3D view will change the way it is drawn in the viewport, the same as changing the size in properties. – gandalf3 Aug 27 '13 at 18:56
• @gandalf3 scaling does affect the visible size, but not the size in the properties. – krivar Aug 28 '13 at 14:57
• @krivar Then I'm not sure I understand.. "The only difference is in how you see the light in the 3D viewport." I thought they both effected the way the lamp was drawn in the viewport, so they would not be different? (The only difference I can see is scaling does not effect the Size in the properties) – gandalf3 Aug 28 '13 at 18:54
• @krivar I also checked again. The actual size of the light is Size multiplied by Scale. This is also the size shown in the 3D View. So in my opinion you should leave the scale at 1, so Size shows exactly the size of the light. – jasperge Aug 28 '13 at 19:22