This past weekend was absolutely beautiful. On top of that, it was one of my favorite times of year in Central Florida – Biketoberfest. Instead of enjoying the beautiful weather on my motorcycle in Daytona, I was sick in bed. Seriously, I slept through Friday and half of Saturday. When your head is spinning around with the flu, it's not a good idea to get on a motorcycle.
By Saturday evening, I was finally starting to get over it and I decided to recover some disk space by eliminating some unnecessary photos from my Aperture database. I was about to delete this image below when I thought I'd share it to illustrate one of the concepts I've mentioned before – how flash helps you take sharp photos.
This came up after some discussion on a photography message board. A few folks were asking about getting into studio lighting and wanted to know opinions on strobes vs. continuous lights. Some folks were proponents of continuous lighting for people learning lighting because they can see where the shadows fall before they take the picture. That's perhaps the only benefit that I could imagine.
I advocated strobes because of its flexibility, power, and duration. After all, the things we see are merely reflections of light. If you reduce the amount of time the light falls on your subject (flash duration), there is less chance for your subject to move and cause blur.
This image below is one of my experiences illustrating both flash and ambient light blur. Otherwise, I'd toss it.
I took this shot at a workshop with my friends John & Susan. The previous shot was too dark on the right side, so I slowed down my shutter speed to allow for more ambient light to enter the image. This shot was ISO 800, f/5.6 and a shutter speed of 1/8th second at a focal length of 135mm. It's pretty hard to hand-hold 135mm at 1/8th of a second. Camera shake becomes more exaggerated as the shutter speed slows and the focal length gets longer. You can see how the fixtures on the right side are out of focus, but take a look at this crop image.
You can see that the side of the model's face is clear and sharp where the flash light fell. Unfortunately, the other side (her left side) is quite blurry due to my camera shake during the 1/8th shutter speed. The ambient light falling on her is continuous light, so it reflects for the full duration of your exposure. The flash duration is shorter than your exposure, though. That's why it's sharp – there's no opportunity for it to keep reflecting light and cause any blur due to movement of your camera or subject.
Mixing ambient light and flash can provide some interesting results. You may want the ambient light to blur, such as a long exposure while traffic goes by. You may also need to re-adjust the direction of flash on your subject. The image below was taken with the same exposure settings and I was able to hold still long enough to keep the fixtures reasonably sharp, but I definitely needed the flash on my model, Megan. This image just wouldn't come together using continuous light on the model.