The Misconception That Flash will Always Freeze Motion
How to shoot motion using flash, or letting the flash do the heavy lifting. It is a misconception that flash will always freeze motion. Why?...because when using flash the image is being exposed by two light sources. Both ambient light and flash are contributing to the final exposure. The trick here is to kill the ambient part of the exposure as much as possible, and let the flash be your dominant light source. So, in essence, you are significantly underexposing the ambient with your shutter speed selection...the above image was shot at 1/200 sec. (just be aware of your camera's sync speed and not go beyond that, unless, however, you have your flash/camera set for high speed sync, but enough of that for now) Needless to say, all this needs to be done in full manual mode and not in the auto or semi auto modes. This, and many of my dance shots were done with never changing the camera settings, all at f/4.5 and 1/200 second with the speedlight flash set to eTTL mode.
A further explanation of a combination of both ambient light and flash's contribution to the final image. The normal default setting on most cameras is first curtain sync. In that mode the flash will fire when the shutter curtains are fully open, and that flash pulse is very fast, maybe as fast as 1/10,000 second, but your camera's shutter at say 1/60 second will continue to add light for that time even after the flash has fired. This is what I mean about two light sources in flash photography. Now, getting back to freezing action which can often be difficult in events like weddings. So, if you are using a slower shutter speed with flash such as 1/60 which many cameras will default to in the various auto modes you can wind up with what's known as "ambient blur," and your flash actually did not stop the action. Remember, it fired at that very moment when the shutter curtains were fully open, say at a 1/8000 pulse of light, but the shutter was still remaining open and letting light and therefore motion into your final exposure, and you wind up with a not so sharp image, very frustrating to say the least. So, kill that ambient light from the shutter by using a faster shutter speed, and as long as your within the range of your flash unit set in TTL mode it will provide 80-90% of light, and at 1/8000 second, it will freeze the action. Hope this provides a better understanding of using flash to freeze action!
The Misconception That Flash will Always Freeze Motion
How to shoot motion using flash, or letting the flash do the heavy lifting. It is a misconception that flash will always freeze motion. Why?...because when using flash the image is being exposed by two light sources. Both ambient light and flash are contributing to the final exposure. The trick here is to kill the ambient part of the exposure as much as possible, and let the flash be your dominant light source. So, in essence, you are significantly underexposing the ambient with your shutter speed selection...the above image was shot at 1/200 sec. (just be aware of your camera's sync speed and not go beyond that, unless, however, you have your flash/camera set for high speed sync, but enough of that for now) Needless to say, all this needs to be done in full manual mode and not in the auto or semi auto modes. This, and many of my dance shots were done with never changing the camera settings, all at f/4.5 and 1/200 second with the speedlight flash set to eTTL mode.
A further explanation of a combination of both ambient light and flash's contribution to the final image. The normal default setting on most cameras is first curtain sync. In that mode the flash will fire when the shutter curtains are fully open, and that flash pulse is very fast, maybe as fast as 1/10,000 second, but your camera's shutter at say 1/60 second will continue to add light for that time even after the flash has fired. This is what I mean about two light sources in flash photography. Now, getting back to freezing action which can often be difficult in events like weddings. So, if you are using a slower shutter speed with flash such as 1/60 which many cameras will default to in the various auto modes you can wind up with what's known as "ambient blur," and your flash actually did not stop the action. Remember, it fired at that very moment when the shutter curtains were fully open, say at a 1/8000 pulse of light, but the shutter was still remaining open and letting light and therefore motion into your final exposure, and you wind up with a not so sharp image, very frustrating to say the least. So, kill that ambient light from the shutter by using a faster shutter speed, and as long as your within the range of your flash unit set in TTL mode it will provide 80-90% of light, and at 1/8000 second, it will freeze the action. Hope this provides a better understanding of using flash to freeze action!