Pixel Dimensions and Image Resolution
The number of pixels along the height and width of a bitmap image is called the pixel dimensions of an image. The number of pixels per inch (ppi) printed on a page determines the image resolution.
The amount of detail in an image depends on its pixel dimensions, whereas the image resolution controls how much space the pixels are printed over. For example, you can modify the resolution of an image without changing the actual pixel data in the image—all you change is the printed size of the image. However, if you want to maintain the same output dimensions, changing the resolution of the image requires a change in the total number of pixels.
Pixel dimensions equal document (output) size times resolution.
A. Original dimensions and resolution B. Decreasing the resolution without changing pixel dimensions (no resampling) C. Decreasing the resolution at same document size decreases pixel dimensions (resampling).
In Photoshop, you can change the resolution of an image.
Example of an image at 72 ppi and 300 ppi
When printed, an image with a high resolution contains more, and therefore smaller, pixels than an image with a low resolution. Higher-resolution images can reproduce greater detail and subtler color transitions than lower-resolution images because of the density of the pixels in the images. High-quality images often look good at any print size.
You can’t improve a lower-quality image by printing it at a high resolution. Changing the print resolution of an image simply makes each pixel larger, which results in pixelation—output with large, coarse-looking pixels. Increasing the print resolution of an image doesn’t add any pixel information to the image. You can make a low-resolution image look its best by picking a print size that makes the most of the pixels it has.
Important: Video files are displayed only at 72 ppi. Even if an image has a higher resolution than 72 ppi, the quality may not be very good when it’s displayed in a video-editing application.
Printing the same low-resolution image at different sizes
A. Small print size B. Medium print size C. Large print size
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