Working With Digital Images
When working with images there are several things that need to be taken into consideration. Two major things are image files sizes and file formats. What file size is best for your project? How do you know which format to use?
Image file formats
Digital Output Formats
Digital output meaning web sites, multimedia and really anything that will have a final output on a monitor. The standard rule of thumb is JPEG for full color images such as photos and GIF for line drawings and illustrations like a logo.
Jpegs show off full color images nicely, with the capability of dropping enough pixels to compress the file yet maintaining the integrity of the image. A properly saved jpeg can show all the vivid details of a photo yet maintain a reasonable file size for digital transmission.
Gifs show off line drawings well because they don’t drop pixels. Really something as simple as a line drawing can’t afford to have the loss in pixels that a jpeg would produce. In addition a gif has the capability of knocking out the background which allows more design freedom.
Print Output Formats
Print means just that, final output is through a printer on to a hard copy like paper. If you are printing a low level image to your home printer you could get away with a high resolution jpeg. If you plan on having professional printing done then you need to format images like photos as TIFF files, and line drawings or illustrations as EPS. These format requirements could vary based on the equipment your professional print shop has so it is a great idea to ask your print representative their requirements up front.
Having just the right image format for your project can mean the difference between crystal clear graphics and fuzzy graphics so take the extra time to save properly in production to save you headaches and even money later in the project.
Image file sizes
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.