Surprisingly, dinner with the governor was a low-key affair.
If you say that something is low-key, you mean that it is on a small scale rather than involving a lot of activity or being made to seem impressive or important. The wedding will be a very low-key affair He wanted to keep the meetings low-key. not intended to attract a lot of attention to an event, subject, or thing
A dark image (possibly underexposed) that contains important detail in the shadow area
A low key image is distinguished by overall dark tones To obtain an effective low key picture, it is important that subject details should not melt into the dark background; the black parts should provide contrast to the few white parts or highlight areas