What is the reflectivity in photography? How big is the contrast?

What is the reflectivity in photography? It should be said that the main body refracts light, and the reflection is strong and weak.

How big is the contrast? If the contrast between light and backlight is large, the details will not remain so much. We need fill light to reduce the contrast. Stop and shoot. Look at Fuji's super CCD. ..

At present, digital counter-orders can only explode. One gear failed to explode.

Fuji's S2..S3 S5. The shooting record has strong details.