How to display a large image using multiple projectors?
Using multiple projectors to show one large image
By combining and and warping images from multiple projectors, you can create projection on a larger and even irregular surfaces. You can choose projectors featured of warping and edge blending function, or use external solution- hardware or PC software, to combining projected images from multiple projectors. We’ve talked about the detail of what to consider and the pros & cons of each different type of solutions in the previous article: How to plan for large projection system. In this article, we want to touch base on all the essentials you need and planning tips if you want to perfectly edge blend multiple projectors:
- Multiple projectors
We’ll dive into this part in below paragraph of “How to decide spec and quantity of projector”. - The capability to crop content into multiple pieces and distribute them to each projector
If you want to scale single image to multiple projectors, it’s necessary that the image has to be divided into multiple pieces. You can choose to play the image from PC with multiple output graphic, however, if you don’t want to play source from PC, for example, media player or live stream from digital camera, a hardware image controller (or so-called video wall controller) is a much better solution in terms of stability, flexibility and ease of use. Please click here for the detail about this topic. In short, with hardware image controller, you can utilize any input source, and you can keep the whole system simple and robust without worrying about compatibility issue of PC or it’s operating system. Besides, it’s not necessarily more expensive, and even cheaper considering future maintenance cost. - A solution to seamlessly blend projected images at the edge
- A solution to geometrically adjust each projected image
Regarding above #3 and #4 points, you can use projectors with built-in “edge blending” and “geometric adjustment” functions (for example, some high end Epson or Panasonic projectors), but they are usually quite pricy. More and more people tend to use projectors without such functions but do it through standalone solution, which can be either edge blending software (need to run on PC) or edge blending controller box. You can refer to following article for more detail comparison :How to plan for large projection system
What is pixel pitch?
An important concept to share: picture quality is perceived according to the viewing distance and pixel pitch. The closer the viewing distance, the smaller pixel pitch it has to be. That’s why the pixel pitch of outdoor LED walls can be quite big, but still looks fine from far away. In our experience, when watching from a distance of one metre, the pixel pitch needs to be equal or less than 1mm. Pixel pitch is calculated by dividing the image size with its resolution. Here’s an example: if the viewing distance is 5 metres and the image size is 20 metres wide, then in order to achieve a 5mm pixel pitch, system resolution needs to be at least 4K – and that means the whole system needs to support a resolution of 4K or above. To summarize, depending on the viewing distance and expected image size, we know how big the pixel pitch should be, then we can decide the first important factor: system resolution. System resolution isn’t just about your projector or source resolution. It equates to the lowest resolution resulting from the whole system: from signal source, controller, transmission devices like connectors and cables, all the way to projectors.
How to decide the spec and quantity of projectors?
With the above concept in mind, we know how to decide minimum system resolution based on image size and space limitation, including viewing distance And if you know the application, you would know the required LUX* based on ambient light. (*LUX means the final brightness on screen. It’s different from ANSI lumen). Then, the next step is usually a series of calculations in order to decide how many projectors are required and in what spec (resolution, brightness and throw ratio). But, here’s a good news: we have developed a handy simulation tool to help you! When you enter the attributes (image size, planned projector quantity, projector brightness, etc) into the tool, it simulates the result of the final image for you, so you don’t need to do all the complicated calculations. Below video shows how the tool works.
Our offerings
GeoBox has a series of non-PC hardware edge blending controllers for the use of combining the projected images from multiple projectors. The high quality image processing technology (4K2K@60hz or 8K1K@30hz, 4:4:4 color sampling, 10bits processor) is designed for professional AV applications. No special PC software is required, a truly robust solution. Please download the document GeoBox edge blending application examples to quickly check which GeoBox solution fits your project.
For more information, please visit our edge blending product page. More news and reference cases can be found on our LinkedIn page and Reference cases page.
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