Think You Might Change Sizes? Make It A Smart Object!
If you’re building a collage, or some other document that has images on different layers, and you think you might wind up resizing some of the images, rather than just dragging-and-dropping opened photos into your main document, make them Smart Objects. That way, when you resize them (especially helpful if you increase their size), it calls upon the original image to make a clean resize (instead of a blurry, pixelated version). To create a Smart Object, you only have to change one thing—instead of opening the photo, go under the File menu and choose Place instead.