It depends on many factor. Usually, 20% to 40% is recommended. This resolution is calculated from the pojector native resolution. The image size will be also one of the major factor. The projection image size from the projector will be determined by the native resolution. For example, WUXGA image is 16:10 and Full HD is 16:9. If user requires 3m image height, then the minimum projection image width will be 3/10*16=4.8m. When the screen size is 8m width, then the overlap region will be 4.8*2-8=1.6m width. it will be 33.3% overlap ratio. If user wants to keep 20% overlap ratio, the image size for each projector will be 4.44m*2.78m. It means the maximum image height will be only 2.78m but not 3.0m. The overlap region will be 0.88m.
In summary, the overlap region is not a fixed number, user can have higher image and use GeoBox geometry alignment to draw the image to the required height but can't enlarge the image beyond projector optical range. It can be drawn back but not extended to outside.
Below are the advantages to add pure hardware edge blending system:
The setting can be stored inside the Box and recalled at any time.
The projector should have good gamma correction and accurate color to avoid the difficulty in image quality fine tune. Usually, commercial projector above 5000 Lumens from famous brand names should be OK to use.
If the environment is in dark room, user needs to select a higher native contrast ratio projectors to reduce the banding issue in the overlap region due to projector optical light leakage. Usually, DLP projector will have higher native contrast ratio than LCD projector. This contrast ratio should be NATIVE but not DYNAMIC contrast ratio.
The life of the lamp is important for public display for long hours. Conventional lamp will last for 3000-4000 hours and Laser can last for 20,000 hours. User needs to choose based on the application and the budget.
If user wants to increase the image height, to do portrait direction edge blending should be considered. In this case, user need to select laser projector. Conventional projector will shorten the life time if it is installed at portrait direction.
If the screen is curved, user needs to consider the throw ratio of the projector. Short throw ratio will cause more image distortion although the installation distance can be shorter. The image distortion should be controlled under 30% to get good text quality. Ultra-short throw ratio will cause too much image distortion. It is not recommended for curved screen applition.
Most of Laser projector has accurate color with high contrast ratio. It should be the best choice for edge blending application.
VNS has provide prodct selection guide for each application category--edge blending, video wall, multiple function video processor. Please check the Product Tab to find out more details.