This is one example of matching light to your subject. I often recommend that, when the light is bright and high-contrast, photographers should seek low-contrast subjects, and this is an example of the opposite: a high-contrast subject shot in low-contrast, near overcast lighting. The shadows are kept under control, but more importantly, the highlights don’t get too strong and start to wash out the colors, or worse, bleach out entirely to white. Delicate textures and contours can be seen easily, and all of the different colors still fall in the middle registers, being rich without fading towards white.
Shooting at f4 helped keep the two lower blossoms isolated in focus from background leaves, but the natural white edges of the primrose petals helped delineate them as well. Though it’s not like they would have gotten lost against the background colors otherwise…