I want to do a landscape 70cm * 100cm of the exhibition board requires 300dpi I want to know how big the picture needs to be when looking for material on the Internet to be able to

This try to find a big picture, but 0.7 square picture is not too big, to ensure that 72DPI can see clearly, you call 300DPI, this also has to do with the printer and paper resolution, you figure again, the printer resolution is not enough (inkjet photo machine), that is also useless, in addition to the resolution of the paper has a relationship with the fine and rough print out is not the same, of course, the design of the draft! The more fine nature is the better.