A Keystone Effect occurs when the gobo light source isn't perpendicular to its intended destination. The result is an image — shaped like a trapezoid — that’s similar to an architectural keystone, from which it derives its name.
Apollo MFG gobo keystoned for 70° horizontal angle.
The angle of the light, artwork aspect ratio, and distance to its destination are critical. Keystoning, as it's called, corrects the unwanted distortion, and is typically required when the projection angle exceeds 30 degrees.
By warping the image on the gobo, the projected gobo design appears undistorted.
Apollo MFG has developed a standardized method for solving your keystoning challenges.
The following details are required to effectively keystone a gobo, or to resize the image:
- Lens Degree of the Fixture
- Desired Projection Size
- Distance from Fixture to Projection Surface
- Projection Surface (i.e. wall, floor, ceiling)
- Distance of Fixture below or above and/or left or right of Image Center
The graphics below demonstrate the last three items:
Understanding the Projection Surface allows us to determine the type of correction needed, which is especially crucial for Vertical Corrections.
When the Projection Surface is the floor, as the graphic above illustrates, adjustment for Vertical Correction consists of different manipulations than if the Projection Surface is a wall, as shown in the graphic below.
A Vertical Keystone Correction is necessary if the image is above or below the Fixture. The graphic below demonstrates the two measurements required: 1) Distance of Fixture to Projection Surface; and 2) Fixture Distance above or below Image Center.
A Horizontal Keystone Correction is necessary when the Fixture is left or right of the desired Projection Surface Image Center. The graphic below demonstrates the two measurements required: 1) Distance of Fixture to Projection Surface; and 2) Fixture Distance left or right of Image Center.
Some keystoning challenges require Vertical and Horizontal Correction. In these circumstances, please include the measurements for the distance of the Fixture left or right and up or down in your keystone request. Apollo will correct for both alignments for a perfectly corrected keystone.
If your circumstances don't match these diagrams exactly, do not worry. Apollo has decades of experience solving complex keystoning problems and is prepared for yours.