In the article “How to display a large image using multiple projectors?” , we explained that picture quality is perceived according to viewing distance and pixel pitch. While, pixel pitch is calculated by dividing the image size with system resolution.  But what is system resolution? It 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. That is, if your input resolution is only full HD or 4K, you are not going to have higher than 4K system resolution even you edge blend multiple projectors with native 4K resolution.  

When system resolution is limited at 4K, if you want to have good enough image quality on a 10m wide wall, pixel pitch will need to be kept at no more than 2.5mm, so user can watch at minimum 2.5 meter away. However, if system resolution can be increased to 8K, the finer pixel pitch allows for improved imagery from shorter viewing distance and improves larger, multi-projector display images. (Refer here for 8K input timing setting procedure.)