Everybody uses zooms today -- in fact, if you looked quickly at the photo above, you might think it is a zoom, but it isn't -- this blog is about why that is important. Zooms are practically the only type of lens most photographers use other than macro lenses, or very long telephotos if a photographer is shooting wildlife. And zooms are great -- they are convenient, practical, and offer a lot of focal lengths in one lens.
A challenge that many long-time photographers have with zooms is f-stops. Most are simply not very fast, meaning they don't have a wide maximum aperture or f-stop, and some are really quite slow. For example, a lot of compact zooms have a maximum (and variable) f-stop of f/3.5-5.6, which is very slow (especially at the telephoto side of f/5.6). For a lot of outdoor photography, that really is not critical since a lot of landscape and close up photography is shot at smaller f-stops, such as f/11 or f/16. But sometimes it really can be worth using lenses that are faster. An f/2.8 lens is four times as fast, meaning it lets in four times as much light, as f/5.6, yet while f/2.8 is fast for a zoom, it is still not considered a fast lens. Fast lenses generally start at f/2 (twice as fast as f/2.8) and often go to f/1.4 (four times as fast as f/2.8 and 16 times as fast as f.5.6).
Nikon has introduced a series of prime or single focal-length lenses that are very fast: Nikkor 24mm f/1.4, Nikkor 35mm f/1.4, Nikkor 85mm f/1.4 and the Nikkor 200mm f2. Such lenses offer some distinct benefits. One thing that a wider f-stop gives is a much brighter viewfinder in dim light conditions. That can be an amazing difference. Another benefit is the ability to shoot in lower light levels. For example, you might be able to shoot at 1/60 sec. at f/1.4 but you could only shoot at 1/15 sec. at f/2.8 -- that could be the difference between being able to get a sharp shot on the trail handheld vs. a blurry image.
Something that has become very much talked about now is the bokeh or out-of-focus background in a photograph. This is hugely affected by these wide apertures. I shot a bit with the 24mm f/1.4 and this was amazing. That's what you see above. That is not a typical look for limited depth of field photos up close. Normally, most wide-angle lenses such as this will define the background strongly, even if out of focus. By shooting at f/1.4, I got some amazing forms and patterns in the out-of-focus part of the image, forms and patterns that do not exist at f/2.8 or f/4, and look very very different than when shot with a telephoto. Another example is below. And typical of Nikon Nikkor lenses, images were sharp where focused even when shot wide open.
Another advantage of these lenses comes with shooting video. One big challenge that everyone faces with video is that you cannot shoot slower than 1/30 sec. (video typically is shot at 24 or 30 fps, which limits that shutter speed). As the light drops, you need something to allow you to keep shooting, and a high ISO is not always a good idea. With an aperture of f/1.4 you can shoot 1/30 sec. at ISO 100 when otherwise you might have to shoot f/4 with that 1/30 sec. at ISO 800.
I am glad to see Nikon putting out new, fast, prime lenses. This has not been a focus for camera manufacturers for a long time, and only Sigma has done much in this area for an independent lens company. In order to get fast lenses, manufacturers must go to single-focal length lenses. I actually like shooting with a single-focal length. It really forces you to think about what lenses do rather than simply changing composition with a zoom.
Rob Sheppard, www.natureandphotography.com