Makeup that looks correct in a mirror can look grey, ashy or heavy in a photograph taken minutes later. The camera is measuring light differently from the eye in several specific ways.
Flashback comes from ultraviolet filters
Some mineral sunscreen filters reflect light strongly in the region a camera flash emits, including wavelengths the eye barely registers.
Under ambient light the effect is invisible. Under a direct flash the reflected light overwhelms the recorded skin tone and produces a pale cast.
The effect concentrates wherever the product is thickest, which is why it shows most under the eyes and across the centre of the face.
Undertone errors amplify on camera
The eye compensates automatically for lighting colour, so a foundation slightly too pink or too yellow can pass unnoticed in a bathroom mirror.
A camera applies a single white balance to the whole frame and does not adjust locally, so a mismatch between face and neck records as a visible boundary.
Matching along the jaw in daylight rather than under artificial light removes most of this, because daylight is closer to what a camera assumes.
Powder removes the cues that read as skin
Skin looks like skin partly because it reflects light unevenly, with some sheen and some translucency across the surface.
Heavy powder scatters light uniformly, flattening those variations and producing a matte surface that the camera records as an even, slightly artificial plane.
Photographic lighting is usually diffuse and already reduces shine, so the powder that controls it in person can be unnecessary in front of a lens.
Contrast collapses under strong light
A camera has a narrower dynamic range than the eye, so subtle shading is compressed and light contouring can disappear entirely.
The compensation, applying more product, works only for that lighting setup and looks heavy everywhere else.
This is why makeup for a photographed occasion and makeup for the same event experienced in person are genuinely different jobs.
Lenses change the face itself
Short focal lengths, including phone front cameras held close, enlarge features nearest the lens and compress those further away.
Proportions shift as a result, and makeup shaped to the recorded proportions can look unbalanced when seen normally.
Checking a look in a photograph taken from a normal distance rather than at arm's length gives a far more accurate picture of how it reads in a room.