One potential problem that can occur when using a custom gobo and projector is "ghosting." This phenomenon occurs when stray light "bounces around" within the projector and creates a blur or halo at the edges, rather than a crystal clear image with sharp edges as intended. This effect is typical especially for theatrical projectors that use lower quality lens systems.
Also referred to as a halo or stray light, "ghosting" is preventable through several measures:
- Use a lower wattage bulb – Using a lower bulb can reduce the intensity of the light, which will help the image come through clearer.
- Use a donut – A donut is a thin sheet of metal with a smaller hole cut in the center that helps blocking the stray light and enhance projection quality. They are specifically design to reduce a halo effect and sharpen the image. The smaller the hole, the better the effect but a smaller hole will also further reduce the projection brightness.
- Use a higher-quality lens – The lens itself can also be the issue. Installing a higher-quality projection lens can provide a clearer image by heightening the sharpness and contrast of your design. For example, we carry "EDTL" lenses for the popular Source Four theatrical fixtures.
You can create a test donut yourself out of cardboard by cutting a one-inch hole in the center and placing it in front of the lens. If this improves the effect, you should consider purchasing a high-quality, permanent donut. If it doesn't, you may need to use one of the other approaches to solving the issue. The type of donut, lens and bulb used will depend on the brand of projector you are using. They are usually only available for theatrical lights but you could make your own for almost any projector. We carry bulbs, lens and donuts at GoboSource.com for all your projection needs. We can also assist with any custom gobo design needs, helping you get the image that will best serve your lighting needs.
