The Image optimization is active by default in ifolor Designer. The Image optimization automatically improves the image quality for physical printing. Only switch it off if you have edited the images yourself.
If the photos have been edited by your photographer, such as wedding pictures (mostly color space, contrast, etc.), it is important that you switch off image optimization when designing one of our products. Otherwise, the activated image optimization would completely overflow the photographer's processing (images are too light/dark, color casts, etc.).
If you have "normal" unedited images, such as smartphone images, it is important that you leave image optimization active when designing one of our products.