It is a poster of 13.5M*5M. What size should the material used in the picture be? And how to determine whether the material or text is too large?

Although inkjet printing does not need high definition from a distance, 2000* 1200 pixels is far from enough.

Generally speaking, this size of inkjet printing, there are few such large materials on the Internet, and they are usually shot or made by themselves.

In principle, the larger the material size, the better, at least 5000x5000 pixels or more (don't use Baidu Google search), and the post-amplification processing is barely possible.

Determining the size and effect of material or text depends on experience, and you can also preview the whole picture in a way suitable for the screen in PS to see the effect.

In addition, you can also look at other people's works of similar size for reference.

Finally, let me remind you that the resolution of such a large size is 50, which is similar to the resolution of 30.