The screenshot here shows some of the different file types you can use to store and send images: jpg, psd, eps, ai, cpt, gif, tif, mac, pct, png… The list goes on.
Here are the questions you need to ask yourself:
Who will be using the file?
If you’re sending the file to someone else, you’ll need to be sure that they can open your file. That means you have to send it in a form they can open with the software that they own. AI means Adobe Illustrator, and EPS or PSD means Photoshop. Chances are your graphic artist or web pro will be happy with one of those; most graphics programs will open one or the other or both.
However, many people don’t own these programs and won’t be able to open those files. If you are sending a file to a casual computer user, go with JPG. More unusual types of files like CPT (Corel PhotoPaint image) should be exported into a more common format, as you see in the screenshot. Corel may be just as good as Adobe, but fewer people have it. Corel can open Adobe files, but not vice versa, so an Adobe file type is a safer bet.
If you’re using the file yourself or sending it to someone who can open all kinds of files, you’ll need to ask another question:
What will the file be used for?
Different kinds of files are best for different kinds of things.
- JPG or JPEG is good for photos. It’s also good for sending to people with limited software options or uploading to online tools. It handles the most colors and is best for things that don’t rely heavily on clear lines.
- GIF is good for illustrations with simple shapes and solid colors, like logos. It can have a transparent background for the image, and doesn’t lose quality when you compress it. GIF can be used for animation, though that’s not common nowadays, since there are better options now.
- PNG is sort of a newer version of GIF. It allows transparent backgrounds and compresses well, which is to say you can make smaller, optimized files without losing quality.
All of these are raster files, which is to say files that you can’t manipulate much. Your graphic artist and web pro would generally rather have vector files.
Raster files are made out of pixels: little dots of color. If you change the size much, you can end up with an image that shows its pixels.
Vector files are made of digital representations of lines and points, so they can get quite big without losing their shape. You should always have your logo in a vector format, so you can use it as your gravatar or on the side of a truck, should the need arise.
You should also send images, except for photos, to your graphic artist or web pro in vector format if possible. A vector image can be manipulated: it can be turned around and stretched and twisted and otherwise changed in ways that a raster image cannot. Vector formats include SVG, AI, CDR, and DRW.
What about layered images?
Images are built in layers. The image below was built as an EPS image. It had a white background layer. The “special offers” icon was on another layer. The photo was on another layer. The words were on another layer. Then I rasterized the whole thing and made it into a JPG, with just one layer.
If I want to change the words on the text layer of the EPS image, it’s very easy — I just go in and type, as if I were using a word processing program. But if I want to change the words on the JPG, it’s more complicated. I can’t really remove or change them. I can paint over the parts that are on a white background with white, but the part that’s over the photo — well, I’d have to paint over them to match the photo. And I charge by the hour.
This is why people working on your website ask you for a layered file.
If you are yourself a graphic artist or a web pro and for some reason you read all this, you should be thinking right now of how much easier it will be for your clients if you send their files to them in a clear format, and ask for exactly what you want.