Lapland is mostly located above the Arctic Circle, which gives the daylight a unique and distinctive tone all year long.
Most remarkable effects of the northern location can be seen during midsummer and midwinter.
Summer stands for constant daylight around the clock. This provides opportunities for long shooting days and atmospheric sceneries that are possible only above the Arctic Circle. In Lapland's northernmost point, Utsjoki, the sun does not set for 75 days during summer.
Lapland's location above the Arctic Circle also means that during the winter season, there is a period of "Polar Night" when the sun remains under the horizon allowing hardly any daylight. This period lasts for a few weeks depending on location.
During this period called "Kaamos" in Finnish, the variance of day and night can still be clearly noted, but the amount of light is very limited. In practice, dusk begins before dawn turns into day, making the light conditions artistically interesting (but technically quite challenging).
Here's a daylight chart for Rovaniemi: