For this composite, I combined a pure white costume in Venice with a snowy landscape in Japan. I had to lighten all the shadows that were in the original shot of the model so it reflected the very soft lighting conditions of the snowfall scene. I also had to match the color tones. The original portrait I took in San Marco Square had a slight yellowish tint from the stonework of the architecture, while the wintry landscape had a slight bluish bias. I also lowered the opacity of the layer containing the model to 82% to blend the two images in an ethereal way. Photoshop is often trial and error. You try various approaches until the results work. I photographed the snow scene with a 500mm lens plus a 1.4x teleconverter, giving me 700mm of focal length. The settings were 1/1000, f/10, and 800 ISO. Interestingly, I captured the model with a 14mm lens, and the settings were 1/250, f/8, and 1600 ISO. When compositing images, the lighting always has to match, but the lens choice doesn't always have to be similar.