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I want big document size but I couldn't. about Zapplink

ZBrush Usage Questions
#1

Hello. Now I am using Zapplink to make a texture.
I intend to make 4k texture, so I want to get big document size in photoshop.
I made front, back , left and right Zapplink views, pressing F key and export it, but the document size is too small to make a 4k texture. How can I get big document size in Photoshop?
Do I need to make a special setting before using Zaaplink?

Thank you.

#2

Have you tried changing the ZBrush document size (in the Document palette) to 4096 before drawing anything on the canvas and using ZAppLink?

#3

yes. I changed document size.
But pressing F key makes my mesh pic really small.
How to avoid it?