I have taken some pictures of persons on a snow field. Unfortunately they mostly are quite dark, especcially in comparison with the surrounding snow. What is the best way to brighten them up (both on RAW-files and on JPEG-files) without destroying the details in the snow?
Note that I already have taken the pictures. The suggestions in other answers can be applied next time, but not this time anymore.
The simple Brightness tools in editors work, but are often the worst choice.
You did not mention which software tools you had, but if you have Photoshop Levels (CTRL L) or any similar histogram tool, then simply adjust the center slider for the best brighter result. it is a great tool for brightness. Or the Exposure Tool in Adobe Raw is similar (but not exactly the same).
This will not much affect the detail in the brightened result UNTIL you increase it enough to cause clipping. The Photoshop Levels center slider is "gamma" and will never cause clipping. The Raw Exposure slider can. Certainly the Brightness tools can.
If in Adobe Levels or in Adobe Raw, then holding the ALT keyboard key while moving the Levels sliders or the Adobe Raw Exposure slider will show any pixels that are being clipped, so you can judge, and you can stop if it seems a problem.
If you are using ACR (Adobe Camera Raw), it has a fill light option that should do exactly what you want, brighten only the dark areas.
