Every pair below came out of this site. Original on the left, result on the right, nothing retouched and nothing cherry-picked. The source material is public-domain historical photography; the credit and licence sit under each pair.

One photograph, only the target age changed

These three use the same 1863 portrait of Lincoln and the same settings. The only difference is the age asked for. Side by side you can see how the gap in years turns into change on the face.

55 → 68　Lincoln (1863)13 years on: the beard and temples turn grey and fine lines appear around the eyes, with the bone structure untouched. The expression here is a little more relaxed than the original — see "One limitation this set shows" below.Source: Lincoln (1863) · Public domain · photo by Alexander Gardner (origin)

55 → 75　Lincoln (1863)20 years on: deeper lines, whiter hair, the eyelids beginning to drop. Clothing, tie, background and framing are unchanged.Source: Lincoln (1863) · Public domain · photo by Alexander Gardner (origin)

55 → 85　Lincoln (1863)30 years on: deep lines across the face, slackening at the jaw and neck, hair almost fully white. This one also kept the original stern expression. Same source photograph, same settings, only the target age differs.Source: Lincoln (1863) · Public domain · photo by Alexander Gardner (origin)

Other results

30 → 70　Chaplin (c. 1920)A 40-year jump: lines, slackening and white hair all arrive at once, but the eye shape and face shape hold, so he is still recognisable.Source: Chaplin (c. 1920) · Public domain · photo by Strauss-Peyton Studio (origin)

40 → 70　Frida Kahlo (by her father)The female path: sex changes how the facial structure is described. Pick the wrong one and the jaw and brow ridge grow in the other direction.Source: Frida Kahlo (by her father) · Public domain · photo by Guillermo Kahlo (origin)

70 → 30　Einstein (1947)Running it backwards: the lines disappear and the hair darkens, but the moustache and hairstyle keep their shape.Source: Einstein (1947) · Public domain · photo by Photograph by Orren Jack Turner , Prin (origin)

60 → 35　Mark Twain (1907)Another one going younger: eye bags and nasolabial folds go, eyebrows and beard stay as they were.Source: Mark Twain (1907) · Public domain · photo by A.F. Bradley, New York (origin)

One limitation this set shows

In the Lincoln set, the 68 and 75 year versions are more relaxed than the original: the eyes narrow slightly and the mouth turns up. The original is stern and that should not have changed.

The instructions already say that the expression, eyes and mouth must match the original, and that lines are carved into the skin rather than smiled into it. Adding a harder version of that rule (do not narrow the eyes, do not smile if the original is not smiling) produced the same result on the same random seed. So the problem is not the wording. The model drifts a little at this fidelity setting.

The 85 year version kept the stern expression, so it is not tied to how large the change is. It looks random. If the expression wanders, run it again — each generation uses a different seed.

What to look at

• Whether the bone structure moved　The shape and spacing of the eyes, the shape of the nose and the outline of the face should be identical. Only skin, slackening and hair colour change. This is the most reliable way to judge whether it is still the same person
• Whether the background and clothing changed　They should not have. The instructions require the camera, lighting, background and clothing to stay put
• Whether the beard and eyebrows survived　This used to be a problem: push the going-younger instruction hard enough and the model treats a moustache as something to smooth away. There is now a line specifically holding it in place

Try it with your own photo