An image with a high resolution contains more, and therefore smaller, pixels than an image of the same printed dimensions with a low resolution. However, increasing the resolution of an image scanned or created at a lower resolution only spreads the original pixel information across a greater number of pixels and rarely improves image quality. To determine the image resolution to use, consider the medium of final distribution for the image. However, using too low a resolution for a printed image results in pixelation output with large, coarse-looking pixels.
File size is proportional to the pixel dimensions of the image.
Images with more pixels may produce more detail at a given printed size, but they require more disk space to store and may be slower to edit and print. Photoshop supports a maximum file size of 2 GB and maximum pixel dimensions of 30,000 by 30,000 pixels per image. This restriction places limits on the print size and resolution available to an image.