Higher-end photo-editing software includes more sophisticated upscaling routines. For instance, change Resolution to 300 and Width to 12 inches for a 12-inch-wide print, and Preview calculates that it will need to upscale the image by 119 percent. In step 2 above, you might change both resolution and unit dimensions if you know the output size and required resolution. (With “Scale proportionally” checked, Preview automatically resizes the other dimension in proportion to the image ratio, avoiding you having to calculate that).

Either enter a new dimension in units (inches, cm, or mm) or a new pixel width or height.

To “upscale” an image, follow steps 1 to 4 above, and then:

It can only fill in new pixels that average adjoining ones. The results will often look blurry when zoomed in at 100% because Preview can’t add new information where it doesn’t exist. If you need more image data than is present in a file, typically because you cropped an image, you can resize in Preview. You can change the density in the built-in Preview app in macOS:Ĭhange the Resolution value with “Resample image” deselected and the relative dimensions change without any loss or gain of information. (Because screen pixels represent millions or even billions of colors, and because printer dots can only reproduce a few colors-as few as black plus cyan, magenta, and yellow on an inexpensive ink jet-higher printer-dot density is required to simulate the color of the original.) For instance, printer software might recommend 300 ppi from an input image to produce a 6-color or 8-color 1,200 dpi ink-jet print. Instead, you need to modify the scale so that it maps in a way a website, printer driver, or service accepts it.

In many cases, the right amount of information is in the image and you don’t need to modify that. (You can also map per centimeter, of course.) Most images are captured at 72 ppi, which makes an iPhone image with the above dimensions 42 by 56 inches (107 by 142 cm) if printed or displayed at 72 ppi.

The pixel density, or dots or pixels per inch (dpi, ppi), which maps pixels against a preferred display size.

Each pixel represents information captured, a sample of the hue and light intensity that passed through a lens onto a camera sensor element.

The dimensions of the image in pixels, such as 3,024 by 4,032 for a modern iPhone photo.

How to change image resolution on mac