digital prints and resolution-quality issues

[alinas50784287]

I'm creating digital art in photoshop which is printed in big sizes also(18"x24" 300 ppi).When I create the art I give this dimensions to the image(18"x24" 300 ppi)

Now there are additional graphics and elements I want to add to the image-the graphics I want to add are 300 dpi but smaller in image size-so I need to scale them-so they fit my big docoment-I'm afraid that during the scaling of the outer graphics their quality will be lost-I'm trying to understand what happens to resolution if scaling-My main concern is the quality of the digital art-the final product-I need it to be 300 ppi at big size(18" 24")so just want to understand the wise way to use external graphics -and how to scale them without harm to the resolution and quality-I'm trying to understand what happens to the quality when I scale this external graphics-do they lose their quality? Does their resolution change ? Does resolution in general changes during scaling?

[Peru Bob]

Can you create your graphic as a vector graphic with Illustrator rather than a raster graphic in Photoshop?

I think that is the only way you won't lose resolution.

[D Fosse]

Any raster graphics you import will align to the base document pixel grid. One pixel for one pixel.