Fill flash outside is photography technique in which the camera flash is deployed to illuminate the darker areas of an image, especially the subject. You should use fill flas when there is a shadow on the subject, the light behind the subject more than in front, and if you close enough to use fill flash. For portraits focus on keeping it subtle, place the subject in an angling position with the sun, and make use of a reflector. For macro photos think over the flash gun, adjust natural light with the flash, and ponder over the flash bracket. And for landscape photography make use of the fill flash to sparkle the foreground, gels are conducive for the color temperature adjustment, and focus on the natural look.