Checking light, shadows and reflections

Start with what the image shows: windows, lamps, signs, skylight, reflected light, and any flash or fill light that could sit outside the frame. Note whether the scene is indoors, outdoors, in daylight or at night.

Under one distant light, shadows on a flat surface can be compared for consistency. Their appearance in a photograph also depends on perspective, the surface, and the objects' positions and heights. Equal-looking objects do not automatically need equal-length shadows in the image.

For a street at night or a room with several lamps, the one-light assumption is a poor starting point. The terrace example above shows why. Explain the visible pools of light before deciding that a dark patch points the wrong way.

Trace a railing, table edge or row of tiles through the frame. Look at the junctions where objects overlap. If a line reappears in an unexpected position, check whether a change of angle, a different object, lens distortion or an obstruction explains it.

For materials, ask how the surface could be lit or treated. Cloth can be glossy, wood can be varnished, and metal can be matte. A surprising appearance is not enough to establish that an object was generated.

Check blur with the same care. Different depths, movement and editing can affect sharpness. Generated pictures can imitate these effects. Record a specific unexplained mismatch; avoid turning “looks too sharp” or “looks too blurry” into a rule.