The eyedropper (pipette icon) allows you to sample from anywhere in the Blender window. The eyedropper can be used to select different kinds of data:
- This is the most common usage.
- Color Ramp
- Dragging the cursor over the window to sample a line which is converted into a color-ramp.
- This is used with object buttons such as parent, constraints or modifiers to select an object from the 3D View.
- Camera Depth
Number buttons effecting distance can also use the eye-dropper.
This is used to set the camera’s depth of field so the depth chosen is in focus.
- E will activate the eye-dropper while hovering over a button.
- LMB dragging will mix the colors you drag over, which can help when sampling noisy imagery.
- Spacebar resets and starts mixing the colors again.