More on Fill Flash

Fill Flash helps bring out details in the shadowed area of high-contrast subjects. This photo of the left front of a truck tractor without flash doesn’t have much detail under the fender. (Click on image to enlarge, then click on back arrow to return.)

Left Front of Truck with No Flash (ZEISS Milvus 50 mm macro lens on Nikon D850.)
To bring out some detail, a flash was added at a reduced power output. Fill flash isn’t intended to light the entire image frame, but only to lighten very dark areas.
Left Front of Truck with Medium Fill Flash (ZEISS Milvus 50 mm macro lens on Nikon D850 with Nikon SB-910 flash.)
While there was a little more detail in the suspension and frame, raising the flash power added even more light under the fender.
Left Front of Truck with More Fill Flash (ZEISS Milvus 50 mm macro lens on Nikon D850 with Nikon SB-910 flash.)
Before you make any photograph, look for areas that are too dark to show details you may want. By varying the power of the flash, you can bring out as much detail as you choose, without affecting the overall exposure.