From the image description, there isn’t enough information to know the exact tool used. The community suggestions point to a few plausible options: an off-camera strobe/flash, car headlights, or natural twilight/moon/moonlit cloud illumination, possibly with a blended foreground/sky exposure.

For this kind of effect, the most useful approach is usually not precise metering of each tree, but controlled test exposures. With flashlights/LEDs, exposure depends on beam spread, distance, angle, and how long you “paint” each subject. So instead of calculating a single exact value, keep your camera exposure fixed and adjust:

• light-to-subject distance
• how long you light each tree
• beam width/aim
• number of passes

If using flash or headlights, a quick burst can create broader, more even illumination. If using continuous light, closer trees will naturally get brighter, so spend less time on them and more on distant trees.

A practical workflow: tripod, long exposure, make a test shot, review brightness, then refine the lighting time and position until the trees balance the way you want. Multiple exposures blended later can also help if the sky and foreground need different treatment.