When purchasing a gobo image projector, one part of the process is figuring out what kind of projection lens you’ll need. This accessory is different from the gobo itself. It determines how far, wide and bright your gobo image is projected. Think of it more like the lens of a camera, while the gobo is the picture you’re trying to bring into focus, and the projector is the camera itself.
Technically a lens is defined by focal length, the larger the focal length, the more narrow the beam. or beam angle. In most cases, particularly in theater or enterprise projection use, beam angle is more useful as a measurement, the beam angle is calculated through the focal length of the lens and the gobo image size Taking the gobo image size out of the equation makes it easier to determine the projected image size by just using beam angle and distance.
Below are three examples that should help you determine the best lens to use for your gobo needs:
Where you are able to project and the quality of the image depend heavily on the projector lens and the true light output of the projector.Long distance projection – For projecting a gobo over large distances you’ll need the right projector first, but you’ll also need to use a lens that projects a tight, narrow beam between 5 and 15 degrees. This is best for use at outdoor festivals or events where you want to shine a gobo image on a building or landscape in the distance.
Short distance, large image – Indoor uses, such as theater stage projection or at a club, require a completely different approach. You’ll have a broader range of projectors to choose from, but you’ll need to select a lens with a much wider beam, typically with an angle higher than 20 degrees.
Brightness – How bright you want your image to appear will also factor into the lens angle, not just the bulb and projector used. The further the distance, the larger the image and the darker the projection. The image size has huge impact on the resulting brightness. For example, if you double the projection size by doubling the projection distance, you end up with only a quarter of the brightness. Likewise, if you need a brighter projection, move the projector closer or use a more narrow lens.
If you’re looking to invest in gobo images, projectors and other accessories, contact GoboSource, and we’ll help you make sure you get the right tools for whatever your image projection needs are.
