The skeptic in me sees source images that appear to be blurred with heavily sharpened after images which don’t tell the tale of what really happened. It makes no sense to me how an image could get better on upsizing, but I do see how upsizing could improve to get closer to the original source image by with improved algorithms that understand what data is lost on downsizing. To help separate fact from fiction, I decided to take an engineering approach to do an analysis of how the resizing tools I have at my disposal really perform.
To do this I started with an original image at full size, then created scaled down versions at 50 percent and 25 percent in Photoshop. Photoshop CC 2020 21.1.2 Save for Web Settings I then took these smaller files and upsized them at 2x and 4x to see how they compared with their original file to better understand what was lost. I took the full-size original JPEG’s and downsized them in Photoshop using the Save for Web (Legacy) feature with the settings shown in the above screen shot with the percentage set to 50% and 25% using Bicubic Sharpener. Its been my experience that this technique works best for downsizing in Photoshop, but your results might vary if you chose a different technique.
