You may often hear the terms ‘fast’ or slow’ to describe a lens or aperture. This has nothing to do with the speed of operation, but to the size of the maximum possible apperture (usually quoted as a suffix to the name of a lens). A Lens with a maximum aperture of f/1.4, for example, is ‘faster’ than similar lens with f/2.8. Because the aperture is larger, faster shutter speeds can be used, which is especially useful in low light conditions.

Another practical benefit of a larger aperture is that the extra light that enters the lens leads to brighter viewing on the camera’s viewfinder-again, useful in low-light conditions.

Zoom lenses often quote two maximum apertures, for example, 18-70mmf/2.8-4. This means that the maximum aperture at the 18 mm end is f/2.8, while the maximum aperture at 70mm if f/4. In reality, the actual hole is the same size but the added focal length (and the maths) changes the f-number. There are several lenses available with a fixed maximum aperture that doesn’t change throughout the focal range, such as Sigma’s 70-200mm f/2.8 lens. These lenses are usually expensive though, and because of the large optics needed to perform the trick, quite heavy as well.

Nikon introduces the Speedlight SB-600, a compact flash packed with impressive functionality inherited from the renowned SB-800. It serves as a solid base for the Nikon Creative Lighting System when used in combination with Nikon D70 or D2H digital SLRs.

When used in combination with Nikon’s latest digital SLRs, the D70 or D2H, the SB-600 supports Advanced Wireless Lighting as a remote Speedlight that can be positioned as one of multiple remote flashes to significantly extend creative possibilities. To assist in such situations, the Speedlight SB-600 also has two Ready Lights located on both the left and right of the front that can be easily seen from a distance. The SB-600 can also emit an audible alert for further assistance.

Auto FP High-Speed Sync enables the use of Fill-Flash even in bright daylight with wide aperture settings for the achievement of outstanding results and new creative possibilities, including the effective blurring for of out-of-focus background elements. An optional color filter set SJ-1 is also available, allowing imaginative shooting to be pushed even further.

White balance is optimized through the use of flash color information obtained by the Speedlight. The SB-600 also features FV lock, which gives the user the convenience of being able to maintain the measured flash value while recomposing the shot to achieve the appropriate flash output for the subject.

It also offers uncomplicated operation made simpler by an easy-to-view LCD with only six buttons, each of which is backlit and simple to understand.

The Nikon Speedlight SB-600 also delivers plenty of style, both in its compact dimensions and a triangular motif consistent with the Nikon D-SLR theme.

The Nikon Speedlight SB-600 comes complete with a Speedlight stand and a soft case, while two flash cables (the SC-29 and SC-28) and the Color Filter Set (SJ-1) are available as options.

Major Features of the Nikon SB-600

• Supports the Nikon Creative Lighting System.
• Supports i-TTL (for automatic balanced Fill-Flash), D-TTL, TTL, Manual.
• Easy-to-view LCD with 6 simple-to-understand backlit buttons.
• Guide Number of 30/98 [ISO100,m/ft], 42/138 [ISO200,m/ft] (at 35mm zoom).
• Auto zoom of 24 to 85mm, extendable to 14mm with built-in wide-flash adapter.
• Same Wide area AF Assist Illuminator as the popular SB-800.
• Advanced Wireless Lighting available with D2H or D70 when used as a remote.
• Auto FP High-Speed Sync (with D2H only); use with fast shutter speeds achieves effective lurring of out-of-focus background elements.
• Flash Color Information – optimized white balance makes use of data from the Speedlight.
• FV lock holds flash value, enabling recomposition prior to shooting.
• Accurate i-TTL flash control achieved through flash exposure monitoring control.
• Design consistent with those of next-generation D-SLRs, with a triangular design element on the top that complements the D-SLR motif.
• Supports optional Color Filter Set (SJ-1).
• Ready light located beside the LCD on the back panel – highly visible even when used as a remote.

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Interchangeable lenses are not unique to single lens reflex cameras, of course. Film cameras that use optical viewfinder windows (called rangefinder cameras), such as the Leica, also have interchangeable lenses. Early in my career I used a Mamiya twin lens reflex camera, which allowed unhooking both lenses (one for viewing, one for taking the picture) and substituting another set.

Swapping lenses lets you change the “reach” of a lens, from wide angle to medium telephoto to long telephoto. Interchangeable lenses let you choose a lens optimized for a particular purpose. Using an SLR lets you choose a lens, whether it’s a zoom or a fixed focal length lens (called a prime lens) that does a particular thing very well indeed. With the availability of interchangeable lenses, you can select a very fast, f1.4 lens when you need one, or choose a lens that’s particularly good in a given zoom range (say, 12-24mm). As you know, however, lenses aren’t infinitely interchangeable. Lenses designed to fit on one particular vendor’s brand of camera probably won’t fit on another vendor’s camera (although there are exceptions), and it’s highly likely that you’ll discover that many lenses produced by the manufacturer of your digital SLR can’t be used with current camera models.

The first thing to realize is that lens compatibility isn’t even an issue unless you have older lenses that you want to use with your current digital camera. If you have no lenses to migrate to your new camera body, it makes no difference, from a lens standpoint, whether you choose a Nikon, Canon, Minolta, Olympus, Pentax, or another dSLR. You’ll want to purchase current lenses made for your camera by the vendor, or by third parties such as Sigma or Tamron, to fit your camera. In that case, you’ll be interested in whether that older lens will fit your new camera.

It’s easier to design a whole new line of lenses for a new camera system than to figure out how to use older lenses on the latest equipment. Some vendors go for bleeding edge technology at the expense of compatibility with earlier lenses.