"dispassionate light" is correct and usable in written English.
You can use it to refer to a kind of light that is not emotionally charged or overwhelming. For example, "The dispassionate light of the moon cast an eerie glow on the street below."
The event that finally persuaded Mr Forbes to see his candidacy in the same light as most dispassionate Americans was his third place position in Tuesday's Republican presidential primary in Delaware.
Only Japhy Weideman's lighting, somber and dispassionate, seems to separate us from them.
Nonetheless, to forge a long, dispassionate film about a man lit by passion above all else is a curious enterprise; Roberto Rossellini was not far from this, in his bio-pics of Pascal and St. Francis of Assisi, but he was a man with "Stromboli" and "Rome, Open City" to his credit, so his acquaintance with the anatomy of the passions was well attested.
In answering this question Stiglitz casts the light of a powerful, dispassionate and compassionate mind, thoroughly informed by his years in international development agencies and as an adviser to the Clinton administration who often found himself at odds with the president's habit of serving individual commercial interests at the expense of hundreds of thousands of third world farmers.
Though she maintains a surprisingly dispassionate tone, this is not an account that paints humanity in an especially flattering light.
Clegg outlines an oddly dispassionate view of work as an activity that can be flipped on and off as easily as a light switch.
He bears dispassionate scrutiny.
He is ineloquent and dispassionate.
Nonetheless he proves himself a dispassionate narrator.
Jurgen's eyes were clear, dispassionate.
