The smaller file is 900 x 600 pixels 150 ppi at a size of 4”x6.”. The larger file is 2880 x 1920 at 480 ppi at a size of 4”x6.”. Both files will print at the same size (4”x6”) if sent to a printer. But one has more information and will technically make a better print. Resolution (e.g. 300 dpi, 240 dpi, etc) affects how your photo ==> your actually wanted formula Lcm = 2.54 * N/(DPI) test: 300 DPI and 600 pixels give Lcm = 2.54 * 600/300 = 2.54 * 2 centimeters = 5.08 centimeters. That's 2 inches. The number 118.1 is 300 divided by 2.54 That's 300 DPI converted to pixels per one centimeter. Note: Often paper sizes are rounded to the nearest full millimeter. The quick answer is that higher resolutions lead to better scans for reproducing your images. 600 DPI scans produce much larger files but help ensure every detail in your print is recorded in digital form. If you want files that are easier to work with, 300 DPI scans would be a better choice. Dots per inch (DPI) je údaj určující, kolik obrazových bodů ( pixelů) se vejde do délky jednoho palce. Jeden palec, anglicky inch, je 2,54 cm. Někdy se také užívá zkratky PPI čili pixels per inch, pixely na palec. Zatímco DPI označuje počet vytištěných bodů na palec obrazu vytištěného tiskárnou, PPI představuje počet a. Try expanding the 300 dpi image to 600 dpi using appropriate intermpolaton (usually bi-cubic) b. Now, subtract one image from the other. You want to get the absolute value of the differences. c. The resulting image will be VERY low contrast. Normalize the contrast. d. Look at the image. ILBi.

300 dpi vs 600 dpi