It does loose all contrast on dark images. Saving battery they brighten the displayed image and lower the back light. This lowers 100% white to maybe a 80% white and makes for horrible contrast.
For those affected:
- you can test if you have this issue here: http://tylerwatt12.com/dc/
- for a fix you can go through the comments here: https://github.com/advancingu/XPS13Linux/issues/2
But be warned, the leaked firmware someone posted does not always work right (but fixed it for me).
If I read the latest comment right there might be an official patch now (after years of this issue). (at least it doesn't say QHD in the file name) (this is what the last comment links to: http://www.dell.com/support/home/us/en/19/drivers/driversdet... )
Want another dell display goodie? Their "display manager" for external displays downloads updates via http, through your browser, from a domain other than dell.com, as an exe, signed by their contractor.