Resolution has always been a tricky subject for new photographers to grasp. After all, there is not a single resolution that we talk about. The quality of the lens optics affects the resolution of the lens. The size and design of the sensor significantly influence the resolution of your camera. Even your image data file has variables that define the image data resolution.
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Day after day we sit in front of our display screens and the number of data points on the screens helps define the display resolution. But technology is changing and defining the resolution of a display isn’t so easy anymore.
Traditionally, display screen resolution is measured in Pixels Per Inch (PPI) and is quoted in the number of unique pixel elements horizontally and vertically. For example, you may have a display that is 1024 pixels wide by 768 pixels high. For a long time, you’d find that displays packed about 72 pixels in each inch of the display. Then, wow, hold on to your hat, manufacturers really upped their game by going to 96 pixels in an inch.
Because these pixel densities were pretty consistent, people began to refer to the display resolution as only the pixel dimensions. But display resolution is not just a count of unique picture elements, it must also include the space. Resolution is the density of the pixels over a set space - in our case inches.
Image ©Apple.
Newer technology has made all this a little tricky. Gone are the days of using 72 PPI or 96 PPI for display screens. Apple’s Retina displays have virtually doubled pixel densities on computer displays. And the displays on our phones have improved exponentially. The new Apple iPhone X sports a display with a whopping 458 PPI.
This technology is driving many changes. If you post to Instagram, you know that the new standard image size has more than double to 1080 x 1080.
Even more confusing is the variety of aspect ratios on the new displays. Remember when XVGA was high-resolution? Now we have HD 720, HD 1080, UHD and even 4K. But these pixel dimensions are spread out among displays with an aspect ratio of 5:4, 8:5, 16:9, and even 17:9.
If you have two 16:9 displays, one with an array of 1280 x 720 pixels, and the other with an array of 1024 x 768, they are going to look quite different. The first, has square pixels, while the 1024 x 768 array is made up of oblong pixels. The elongated pixels can certainly reduce the perceived sharpness of your image. It can also distort the image.
The good thing is that many of these new displays use special image processors to scale the image properly but it is always best to use the native resolution of the display and provide an image file that that is large enough to take advantage of all those extra pixels.