For anyone who has ever been confused about high resolution, low resolution and dpi, you are not alone. Just reading a few of the countless articles out there even on the “basics” can make your eyes get blurry and your head feel like it is going to explode. As a newcomer to the web design business, I was given the task to research and write on the subject of resolution and dpi, and let me tell you, I don’t know how you guys keep it all straight.
Just when you think it’s broken down into the simplest form, you find fifty sub headers about how dpi doesn’t actually mean “dots per inch” if it’s used within a certain context (what the heck, I’m lost again). So, I will try to give an amateur and basic explanation on high and low resolution along with what it means when an image is dpi.
Essentially, resolution means the detail that is in an image. Higher resolutions will contain more detail than lower. If you’ve ever looked at a print ad or even a photo online that was blurry and undefined, that means it is low resolution. Images that are clear and detailed are high. Low is best for online, due to the fact that a lot of web graphics and online photos are normally created at 72dpi (dots per inch, which we will get into next). It’s suited best on here because it makes file sizes smaller, therefore pages load quicker. Computers generally capture images at 72dpi, but then once someone tries to print the same picture, though it may by clear on the screen, it will print out jagged and hazy. 300dpi is used for print publications or commercial printing. This is the resolution you see when pictures are clear, glossy, and detailed. One exception is newspapers, due to the fact that they are in black and white, so they can be a lower resolution than color photos.
So, now what is dpi? Well, dpi stands for “dots per inch” or the amount of pixels per inch of an image. The more pixels it contains, the sharper it looks, which is why 72 unlike 300, will be blurry if printed. Dpi sometimes gets confused with pixels per inch (PPI), but that is different. Wikipedia breaks it down into layman’s terms;
Dpi-is the measure of spatial printing or video dot density, in particular the number of individual dots that can be placed within the span of one linear inch.
Ppi- or pixel density is a measurement of the resolution of devices in various contexts; typically computer displays, image scanners or digital camera image sensors. Ppi can also describe the resolution in pixels of an image to be printed within a specified space.
It is important to note (or maybe just for myself since I know I’m guilty of this) that trying to expand or stretch an image that is low resolution will not suddenly make it high resolution. It will only make it larger, while still retaining the blurriness.
What I found to be the best example for those of us who are still confused, was on the website; http://www.mmprint.com/highres_photos.cfm . This shows the 72dpi screaming baboon versus the 300dpi screaming baboon. It is obvious in which resolution it is easier to make out the details. Along with the baboon, another good example, if you head to the website, http://dx.sheridan.com/advisor/image_resolution.html, there is a photo that you can change from high to low resolution to view the difference.
Finally, it is crucial to know the guidelines for your situation. You should never be sending out pictures to be printed that are grainy and not ascetically pleasing. Paying attention and understanding what resolution is expected is the first step to creating impactful and successful advertisements, websites, or photographs.