If you have doubts about how a particular image will print you can zoom in to view it at 200% scale aka the 200% test. This will give you good idea of how the image will look in print. Here's how to view your image at 200% using the Preview feature on a Mac.
- Open the image in Preview on your Mac.
- Add the scale box to your Preview toolbar if you don't see it by going to View > Customize Toolbar and dragging the Scale item to your toolbar.
- Enter 200% in the Scale box and inspect your image for grain, blurriness, and pixelation. If you see any of these issues at 200% scale, then the image will look that way or worse in print, and you may want to avoid using that image.