Why should you care about understanding DPI & Resolution? Well, if you are going to print something of quality or are ever tasked with optimizing images for the web, knowing a few things will save you time and give you the best results.
On the flip side, if you ever hire PMD Group to develop print materials or build a website for you, we have requirements that may be difficult to understand and not everyone is good at explaining them. It can be confusing and hard to explain so here’s what you need to know.
It’s important to begin with a high-quality image which means the highest resolution and image dimensions you can get. When it comes to source images, just like Texas, bigger is better. You can go down in size, but not up, without losing quality.
Definitions:
DPI: Dot’s per inch. The number of dots in a printed inch. The more dot’s the higher the quality of the print (more sharpness and detail.)
PPI: Pixels per inch. Most commonly used to describe the pixel density of a screen (computer monitor, smart phone, etc…) but can also refer to the pixel density of a digital image.
Resolution: Resolution is the measure of pixels in the display, usually expressed in measurements of width x height. For example a monitor that is 1920 x 1080 is 1920 pixels across and 1080 pixels down.
Higher resolution means more detail. Higher DPI means higher resolution. Resolution is not “size”, but it’s often confused with it because higher resolution images are often bigger, but that doesn’t necessarily have to be the case.
Print: 300dpi is standard, sometimes 150 is acceptable but never lower, you may go higher for some situations.
Web/Digital: DPI doesn’t equate to digital it’s a print measure. It was commonly believed for a long that 72dpi was ideal for web. If you hear that it’s simply not the way things work. When talking digital, we’re concerned with the actual resolution. How that image prints is another matter.
If you are creating images to use for print and the images are “too small” the odds are the resolution wasn’t high enough. The image might look huge on your computer but still print out quite small. To add to the confusion, your screen resolution will also determine how big the picture appears to you when viewing it on your computer.
Hopefully this has helped you understand DPI, PPI, resolution and why if you have someone do something for you in print there will be different requirements than for the web. It’s also why that digital camera with higher megapixels takes better pictures than one with lower (lenses and other factors being equal), because it gives you more resolution to capture more detail. Image files with higher resolution (more dpi) will also have a bigger file size because they contain more data. Start with the biggest images you can but when putting images on the web they should be set to 72dpi, it’ll save bandwidth and they’ll load faster. Yes, they’ll be smaller than the original but should in most cases be plenty big because of monitor resolution (ppi) sizes.
Don’t confuse “image size” with “file size.” Image size refers to the dimensions of the image while file size is how much space the image takes up on a hard drive (kilobytes or megabytes.)