Changing the pixel dimensions of an image is called resampling. Resampling can degrade image quality. Downsampling decreases the number of pixels in the image, while upsampling increases the number.
The detail in the original image (left) is crisp; the detail in the upsampled version (center) is slightly blurred; and the detail in the downsampled version (right) is lost.
|Pixel dimensions||Size||File size|
|Left image||470 x 1000||2.75" x 4.75" at 240 ppi||1.34MB|
|Center image||940 x 2000||2.75" x 4.75" at 480 ppi||5.38MB|
|Right image||157 x 333||2.75" x 4.75" at 80 ppi||153K|