A misty scene need not have the same contrast as a photograph in harsh sunlight. Yet a histogram with empty ends can tempt you to stretch the tones as far as possible. Black and white points are tools for an intended rendering. They are not instructions to force both pure black and pure white into every photograph.
Distinguish endpoints from midtones
The black point determines which dark values map to black. The white point sets the bright endpoint. Moving these limits too far into existing image values can merge distinct dark or bright details into the same output brightness. In a finished JPEG, that loss cannot simply be undone.
A dark face therefore cannot always be brightened sensibly by changing the black point. An exposure or local tonal adjustment may be more appropriate. Likewise, improving dark midtones should not require sacrificing texture in important white fabric. Separate the question of endpoints from the brightness of tones between them.
Examine a subject with dark fabric
Consider a black jacket against a grey wall. Lowering the black point may give the jacket more depth while leaving folds visible. Going farther removes seams and merges separate areas into one untextured shape. Compare normal and enlarged views to identify where this transition begins.
Small dark gaps may appropriately become black. The aim is not to preserve every pixel distinction, but to retain important information about the material. A clipping display helps locate these areas; deciding whether they matter remains a visual judgement.
Preserve deliberately soft contrast
In fog, snow under diffuse light or a bright product scene, empty histogram ends may be appropriate. Aggressive stretching would change the atmosphere and exaggerate small imperfections. Check whether subtle tonal differences already describe the necessary shapes.
Reassess endpoints after substantial colour or contrast adjustments. Another curve or stronger saturation can push individual channels to their limits. Preserve an editable version and inspect the actual exported file, since a small preview can easily conceal missing detail.
