Hey guys

Ive got this texture (had to cut it due to the size) but this is huge. I mapped it onto a plane for displacement and got this result.

Ok what I wanted ive achieved. But i have to do this on a much bigger scale. Meaning that etxture has to be made smaller and copied so its tileable.

However, when i do this it greatly reduces the quality of the texture.

My quesiton:

How can i reduce an image in photoshop so the quality isn't reduced?

Thanx