It is important to understand how to size image files accordingly to how you plan to use them. For example you would have a larger file size for print output so the image would remain crisp and clear throughout the entire process. For digital output you would have smaller file sizes so the image would transmit faster. For example you want the images on a web site to load quickly or a visitor might get tired of waiting and leave without seeing a thing.
For digital output you need to look out for two things. First make the image the exact size that you are going to use it. So if your web page has a space for an image that is 200px x 100px (px stands for pixels), then you need to open the image in a photo editing program and make it exactly 200px x 100px. Of course apply this theory to whatever size the image is being used for.
The second thing to look out for is setting the dpi correctly. The standard is 72 dpi, but I have had some less than perfect quality images that didn’t look good at 72 dpi so I made them 150 dpi instead. Use your best judgment, obviously the smaller image file size will open faster but we don’t want to sacrifice quality or really what point is there for even having the image.
The standard rule of thumb for professional printing is to set your images to 300 dpi, however some digital printers work better with 250 dpi. As you can see this is a much larger size than digital output and it should be. Printers are made to take the larger files size and in fact require it to produce a crisp clean image. As always I recommend asking your printing representative what file size they recommend since different printers can vary in requirements.