Prompting Product Photography: Light, Surface and Reflections

Product generation seems easier than portraiture: no face, no anatomy, no likeness. In fact it imposes its own set of demands, the chief one being physical credibility of surfaces.

What matters in a product frame

A viewer judges an object by three attributes: form, material and how light sits on it. The first is reproduced confidently for common objects; the second and third need explicit description.

Materials and their behaviour

• Matte surfaces (ceramic, raw wood, fabric): scatter light, soft transitions, easy to generate.
• Glossy (lacquer, plastic, glaze): produce crisp highlights whose position must match the light source.
• Metal: reflects the whole environment, not just the source. The hardest material.
• Glass and transparency: requires correct refraction and what is visible through the object.
• Textured (concrete, stone, coarse fabric): benefit from raking side light that emphasises relief.

Light for objects

Unlike portraits, where soft light is almost always safe, the choice for an object depends on its material.

1. Matte — soft diffused light from above or the side, a light shadow for volume.
2. Glossy — a large soft source giving an extended highlight; a point source produces a hard white dot.
3. Textured — directional side light at a shallow angle to the surface.
4. Transparent — lit from behind or below so the form reads.

Shadow and surface contact

The commonest error in product generation is an object floating above the surface. There should be a contact shadow between object and base: a darker area directly beneath it.

State it directly in the request: "a soft contact shadow beneath the object", "the object rests on the surface". Without it the model often leaves the object hovering, and the frame looks assembled in an editor.

Background and surface

For product work the background should almost always be simple: not competing with the object, not distracting.

• "A plain light grey background with a gentle gradient" — the universal studio option.
• "A concrete surface, soft shadow" — a popular contemporary look.
• "A wooden table, natural window light" — a warm domestic scene.
• "A white background with no shadows" — the catalogue standard, requiring an explicit note about the absence of shadows.

Angle

Three working options: straight overhead (flat lay), three-quarter (the most informative) and at object level (emphasising height and form).

The choice depends on the object: flat items read from above, three-dimensional ones in three-quarter, tall ones from their own level.

What will not work

• Exact geometry of a specific product: the model builds a similar object, not that one.
• Logos and lettering on packaging: they turn into pseudo-text.
• Complex mechanisms with fine detail.
• Accurate colour for a catalogue: the shade will be approximate.

Hence a practical boundary: generation suits image and atmosphere shots, but not product cards where a buyer decides from the picture.

Compositions with several objects

Each additional object complicates matters disproportionately: relative placement, scale and a shared shadow all have to agree.

The practical limit is two or three simply shaped objects. Beyond that the composition starts to fall apart: objects intersect incorrectly and shadows run in different directions.

Checking the result

1. Is there a contact shadow, and does it match the light direction?
2. Are highlights on glossy surfaces where the source should be?
3. Is the object symmetrical where it should be?
4. Does the material read unambiguously — does metal look like metal rather than grey plastic?