The Sweet Zone is the period of time when the sky begins to light up before dawn or the light fails at dusk when the flash on your camera still functions at the same time. Your camera uses both the flash and the natural light to create a unique image that cannot be caught at any other time of the day. The Sweet Zone only lasts about 10 minutes. Before that time there is usually not enough light for your camera to pick anything up or for your flash to function. After it the flash stops functioning completely and natural light takes over in the shots. You can force the flash to remain on, but it is only in that brief zone that you can pick up some very intriguing outdoor images.
The sweet zone does not function when taking just distant skyline images. There must be objects close up to reflect the flash and enough sky to show through from behind. Here is an example:
This is an untouched image. No enhancements or changes made. You can see how the close proximity of the nearby tree and spanish moss is illuminated by the camera flash yet the deep blues of the emerging dawn sky show through clearly.
If you catch the image too soon you basically capture very little detail as shown here:
In this case the sweet zone had not quite arrived and the camera was basically relying only on its flash to supply light. The tree was also a bit far away so picked up very little of the flash.
Here you see a finished image which has gone through digital post processing:
The flash reflected off the brick structure while still allowing the daylight to come through behind. Another 2 minutes and this shot probably would have been impossible.
Now I am sure there are technical names for this, but I am not writing this entry for tech savvy camera people. I am writing it for the artist who is also the photographer and looking to enhance their work with something different.
The countess variety of images I've gotten during the sweet zone has been a joy to me as a photographer. I hope it is for you also.