Put a Subject Somewhere Else, Convincingly

How it works

Your image is scaled to about one megapixel and repainted at a high denoise with a fresh seed each run. The instruction asks for a new setting and, in the same breath, for the subject to be relit to match it — shadows moved, rim light moved, and the color of the light on skin and clothing changed to agree with the new surroundings.

The negative prompt is a list of composite failures rather than image artifacts: a cut out edge, a halo outline, mismatched lighting, a wrong shadow direction, a missing contact shadow, and a floating subject.

This is the opposite approach to the other background pages here, which cut the subject out and leave it untouched. The trade is deliberate and it is explained below.

Four things that give a composite away

Ask someone why a composite looks fake and they will usually say the edges. Show them the same composite with the edges perfect and they will still say it looks fake. The real signals are these.

Direction. The shadow under a nose, a chin, a shelf, or a shoe points away from the light. If the subject's shadows point one way and everything behind them points another, the picture contains two suns and the viewer notices in the way they notice a wrong note.

Temperature. Interior tungsten is warm, overcast daylight is cool, shade is bluer than direct sun. A subject photographed under one and placed under another is a different color from their surroundings, and skin is the thing people calibrate on most reliably.

Spill. Environments throw light back. Grass puts green under a chin, a red wall warms one cheek, snow lifts the underside of everything. A subject with absolutely no color from their surroundings is a subject that was not there.

Contact. Wherever a subject meets a surface there is a dark, tight shadow. It is small and it does almost all of the work of putting weight on the ground. Leave it out and the subject floats, however good the outline is.

Why this page repaints the whole frame

A cut-and-paste pipeline can fix none of the four, because the subject's pixels are fixed the moment they are cut. You can grade them, but grading applies one change to all of them and shadow direction is not one change.

Repainting removes that constraint. The model produces subject and setting as one picture, so the relationship between them can be right by construction rather than corrected afterwards.

The cost is honest and it is significant: the subject is being generated, not preserved. Faces drift, patterns on clothing wander, small objects change. That is the trade this page makes, and if it is the wrong trade for your image — a product that must be exact, a person who must be exactly themselves — the studio backdrop page keeps the subject pixel for pixel and gives you less freedom over the setting.

Choose a setting your lighting can support

The single most useful habit is to pick the new background to suit the photograph you have.

A subject with strong light from the left works in any scene where light comes from the left, and fights every scene where it does not. A softly and evenly lit subject is compatible with almost anything, because there is no emphatic direction to contradict.

So if you can influence the original shot, shoot it soft. And if you cannot, look at which way the shadows fall before deciding where to put them.

Publication gate

This page ships once the workflow has been run against a softly lit portrait, a hard side lit subject, a full length figure where a contact shadow is required, and a subject in a strongly colored room, checking direction, temperature, spill, and contact in every output.