Vignetting with flash - The Royal Albatross.

On-camera flash is a marvelous tool that can be used to shoot in dark areas and fill shadows.  Its ability to light up areas close to the photographer is limited due to its power and inability to alter dispersion patterns.   Since it is so close to the lens two additional issues pop up.  The first is the occurrence of the notorious "red-eye."  The second is what this blog is about, vignetting.

Vignetting, in photography, refers to the darkening of an area.  Most lenses suffer from some degree of vignetting where the image becomes darker as it progresses to the outside edges.  It tends to be most noticeable in corners as they are the farthest away from the center.  Fortunately, this problem is often mitigated with onboard software inside the camera or with a pixel-editing program such as Photoshop.

The second type of vignetting occurs with flash and can be seen in the above photo.  Since the lens sticks out in front of the camera, just underneath the flash, there is a chance that it may block the progression of light in lower aspects of the shot.  This likelihood is compounded in situations where a lens is physically long, a wide-angle focal length is selected, the subject is close to the camera, or a lens hood is mounted on the end of the lens.  Each of these by themselves represents a risk in creating vignetting, but a combination of them increases the probability significantly.

In the above photograph, a Panasonic FZ2500 all-in-one camera was used to capture the photo.  It has a relatively large lens in its own right, even when the widest angle focal length is selected.  Since it projects so far in front of the camera's flash there is a good chance that it will block some of the light from hitting the image, creating a vignette.  Shoot near a subject with a lens hood on and the likelihood becomes a certainty. 

There are several ways to prevent this or reduce the effect.  Photographing a subject farther away with a bit of zoom will help.  Since a flash's ability to illuminate a scene is reduced by distance and decreased aperture size (increased f/number), the camera's ISO may have to be increased to compensate if the shot is coming out underexposed.  Taking off the lens hood also helps. 

Two additional solutions are somewhat costly.  An external flash sits higher atop the camera and vignetting becomes all but moot.  It also addresses power and red-eye issues.  A shorter wide-angle lens, such as a prime 24 or 28 mm, is stubby enough that it won't get in the way of a built-in flash, unlike some of the multipurpose zooms out there which are very long.

Thanks for reading.   www.ericspix.com