During my January trip to Oahu, I captured a sunrise at Waimanalo Beach in Honolulu. It rained throughout my hour long drive to the beach in the dark. I arrived at the beach well before sunrise. The chances of getting to see the sun through the thick cloud cover seemed bleak.
About fifteen minutes before sunrise I started taking pictures. For the first picture in the sequence I set the camera for a long exposure. The long exposure helps to smooth out the water.
Just before sunrise, the clouds cleared enough at the horizon to allow the sun to appear. I captured a second exposure right at that moment. For this exposure, I dramatically underexposed the shot so that the sun wouldn't completely blow out that portion of the sky. I also selected an aperture of f/20 for this frame to help reveal the sunburst.
A few minutes later, I was thrilled to see that the sunlight was radiating into the clouds above. The golden reflection in the water also made its appearance. So, I captured a third exposure to include these critical elements into the scene.
Finally, I captured a fourth exposure of the darker clouds in the sky. Here's the final image:
And here's a basic illustration of how the four exposures were used within the frame:
I used Photoshop to blend these four images. Basically, each of the exposures is placed onto its own layer. A black mask is applied to each layer and then a white brush is used to reveal the appropriate segments of each picture. Of course, it's important that all four pictures are aligned. My camera was secured to a solid tripod during the entire photo shoot.
Without using the power of post processing, I would be limited to selecting just one picture to capture the scene. I would probably select the frame when the sun first appeared on the horizon. To help illustrate the power of blending the moments in time, following is the file (straight out of camera) of that one picture. Of course, I would do some basic adjustments (i.e., brightness, contrast, etc.) to this file--but without using multiple exposures I would lose the smooth water and the light rays on the clouds. For me, the light rays on the clouds is the most important element of the photograph!