I went for a walk at sunset today on Damarakloof farm, where I am currently staying and took a few photographs with my Canon 7 D as I went. I will show you a few examples of the pics that I took with and without flash. I used the pop up flash on my 7D to show that you do not actually need a high powered flash to get breathtaking images (although it certainly can help). I used aperture value with the natural light pics and switched over to manual exposure when using flash.
The important thing to remember when using flash is that the shutter speed controls ambient light and the flash and aperture value exposes the subject that is within range of the flash. The ISO speed will determine how powerful or how far the flash range extends. For a really dark sky and background, use a shutter speed of 1/200 to 1/80. For a brighter background or if the ambient light is quite dark then use a shutter speed of 1/40 to 1/80 seconds. You also need to use negative flash compensation to tone down the power of the flash if the subject is quite close.
These pics are unedited and are as shot.
Please let me know what you think of this post and if it inspired you to get creative with flash.
This pic was taken without flash. 24mm F9 1/10sec ISO- 800 (Notice how flat and lifeless the image is)
For this pic I switched to manual exposure, dialed in minus 2 stops of flash compensation. F5.6 1/80sec ISO-320 (Notice how moody the sky looks, with the foreground exposed as well.
No flash, Exposure 28mm F4 1/30 sec ISO-1600
F4 1/200 Sec ISO-800 with pop up flash set to no flash compensation.