Sunday, August 01, 2004

Look cool with lens shades

Mark M. Hancock / © The Dallas Morning News

Hall Office Park in Frisco features the Texas Sculpture Garden throughout the front four acres of the complex. This sculpture is a big steel piece titled "Blanco #17" by Ovilla artist Mac Whitney.

I wrote a long entry about lenses and filters. Since the actual entry would be huge, I'm breaking it apart to make each entry manageable for average readers. Today I'll discuss lens shades (also called lens hoods).

Lens shades are one of the easiest and cheapest ways to improve images. Even a cheap shade is better than none.

Most SLR lens shades screw onto the front of a lens or mount on the barrel exterior. Inexpensive rubber shades will perform well for most PJs. As the lens quality and expense increases, some PJs may opt for metal or hard carbon-fiber shades.

Carbon shades are very expensive but provide better light control and lens protection. They also don't interfere with other screw-on lens filters. For studio shooters, there are bellows-style hoods, which offer superb light control and flexibility, but are more delicate.

Lens shades are sold in different sizes (measured in millimeters). This is a measurement of the diagonal distance of a lens filter mount. Some lenses have this information printed on the front near the objective lens (the most forward lens element).

If ordering online or via mail, this is a critical fact to know. For example, I have four old Nikon lenses (28mm, 50mm, 100mm and 80-200 f/4) which can all use a 52mm lens shade. Modern lenses typically have dedicated barrel-mounted shades.

The best bet is to take all the lenses to a local camera shop and get assistance. If in doubt, ask for the cheapest shades. You can always upgrade later.

The shade's purpose is to block stray light from entering the lens and keep the image's appearance sharp (extremely well focused). By blocking stray light, image contrast is increased. The shade keeps the dark areas dark by removing stray light particles, which gives the overall image a washed-out ("flat") look on a non-shaded image.

Shades also take the brunt of impact damage when the camera hits something or is dropped. I have a box full of broken and bent ones to prove this point.

A shade helps keep rain, snow and side-blowing dust away from the lens or filter. It doesn't eliminate these problems; it lessens the effect.

If the lens is facing into the wind during a storm, the lens still gets soaked. Whenever possible, PJs shoot with the wind to our backs while covering news during a storm and the shade helps keep water drops off the lens.

As with raindrops, the lens shade helps with most lens flare. Lens flare occurs when light from a strong source (the sun, spotlights, a strobe, etc.) directly hits the lens from an oblique angle (see photo above).

Flare aberrations appear in the image area as bluish polygonal areas (matching the number of aperture leaves). One aberration is typically present for each actual internal lens element the light penetrates.

Often, lens flare ruins an image. If used wisely and with knowledge, it can become a cool effect. As a rule of thumb, avoid it whenever possible.

To avoid other problems, make sure the lens shade is appropriate for the lens it's placed upon. There are wide-angle, normal and telephoto (long-lens) shades. Each is designed to give maximum shade while allowing the proper angles of light to enter the lens.

If the wrong shade is used, a "vignette" or "keyhole" effect occurs. The vignette can produce a darkening and diffusion of light at the edges of the frame. A more profound vignette actually intrudes into the image area and blocks out all light from large areas around the corners of the frame.

Since shades are often one of the cheapest accessories PJs purchase, I suggest putting a dedicated shade on each lens. Over time, PJs learn to feel for the shade in the dark to know which lens it is.

As a bonus for the pros who suffered through this entry, when the exterior band of a rubber shade rips off, it's the perfect size to wrap snugly around a flash head to hold color-correction gels or softboxes.

Enough for now,

1 comment:

Mark M. Hancock said...

Test comment section.