Exposure is not simply brightness
Exposure describes the amount of light recorded when the photo was captured. An editor's exposure control shifts tones in the stored image; a brightness control often changes them by a different curve. Neither can reconstruct clipped sensor detail. The photo panels above are display-brightness illustrations, not a simulation of camera exposure.
Contrast and tonal regions
Contrast increases separation between light and dark tones. Highlights affect bright detail; shadows affect dark detail. Whites and blacks set the brightest and darkest endpoints. Lifting shadows can reveal stored detail, but it can also reveal noise; pushing blacks too far removes separation in dark fabric or hair.
A flat white area contains no recoverable texture in this exported image.
Use a histogram as a warning
A histogram counts pixels by brightness from dark on the left to bright on the right. A pile-up hard against an edge can suggest clipping, but the scene may intentionally contain true black or white. Inspect the actual image too: a white lamp can clip without the whole photo being overexposed.
A practical check
Compare a bright window and a dark sleeve separately. If the window is a flat white patch, lowering display brightness will only make it gray; it will not recover texture. Pixlena does not currently offer exposure controls, so make tonal corrections in an editor before using its export tools.