How to overpower bright sunlight with on-camera flash
The photograph on the left shows one of the toughest lighting conditions you get to deal with. Your subjects are half in the sun / half in the shade ... and there is no way you could interrupt and change things in your favor. There is no way to have the flower-girls move. No way to bring in additional, off-camera lighting. You can't scrim the sunlight either with large reflectors.
There are these times when your options are limited, but you still have to get the best out of this challenging situation. There is one viable option Read more inside...
Flash photography: applying the Sunny 16 Rule & Flash Guide Number
In essence, if you know the GN of your flash, then you could use (bare) off-camera flash to match the sunlight, without even metering!
There is a super-useful shortcut built into those two simple values: Sunny 16, and the Guide Number.
Now, I am pretty sure that when you hear mention of the Guide Number of a flash, you're most likely switching off already, thinking that it is just an arcane list of numbers - different apertures against different power settings. But hang in there - this is very useful stuff Read more inside...