A group of compact, lightweight all-in-one zooms—Sony DT 18-250mm ƒ/3.5-6.3, Nikon AF-S 18-200mm ƒ/3.5-5.6G ED VR II, Sigma 18-250mm ƒ/3.5-6.3 DC OS Macro, Tamron 18-270mm F/3.5-6.3 Di II VC PZD.
Evaluating Distortion: Most superzooms exhibit barrel distortion at the wide end and the telephoto end. There are some that have the most distortion at intermediate focal lengths. It's best to test a potential superzoom purchase on your camera to see how it performs for you. You also can check out The-Digital-Picture.com, where there are a number of published tests using ISO 12233 resolution charts. Always buy from a store that allows you to return an unsatisfactory lens. As far as sharpness goes, if you shoot handheld, or at moderate or higher ISO settings, you probably won't notice a big difference between a superzoom and a shorter-range zoom or prime lens. If you work from a tripod, focus manually and use a low ISO setting. You'll see the difference between a superzoom and more costly lenses when you make big prints.
AF Vs. Manual Focusing: While today's AF systems are terrific, able to handle all sorts of quick action, many landscape pros prefer to carefully focus manually, especially when great detail is important and large prints are to be made. Using live view lets you zoom in on the area of interest to check critical focus. Some cameras offer focus peaking, where in-focus edges are highlighted in a color. A helpful accessory is the Hoodman HoodLoupe and the Flashpoint Swivi, which fit over the LCD monitor, blocking extraneous light and providing a magnifying eyepiece. If you don't use such a device, cover yourself and the monitor with a jacket or dark cloth, as view-camera landscapists do, for easier viewing in bright lighting. Note that live-view manual focusing is best done with the camera on a tripod; if you shoot handheld, use the eye-level finder.
Of course, when optimal sharpness is required, as in landscape work, a tripod is a necessity. It's a pain to lug a tripod into the field, but camera shake will negate the sharpness you paid for when you bought your lenses.
Adding Primes To Your Kit
A good prime lens will outperform a zoom that includes its focal lengths because it can be optically optimized for just the single focal length. A zoom must be corrected for a range of focal lengths, and something that makes things better at the wide setting might make things worse at longer focal lengths, and vice versa. A zoom lens also contains more elements than a prime lens, and each element adds weight and additional surfaces that can cause reflections and a loss of contrast. Prime lenses also can be much faster than zooms, often ƒ/1.4. Landscape shooters generally will be shooting stopped down, but travel photographers, and especially sports and wildlife action shooters, appreciate the faster shutter speeds possible with faster lenses.
Once you've shot with your outdoor zoom(s) for a while, you might find yourself gravitating toward certain focal lengths. If a large percentage of your images are made at or around a specific focal length, consider getting a good prime lens of that focal length and supplement with zooms.
The AF motor (for lenses that contain one) also can be optimized for a prime lens. Wildlife and sports photographers will find that the 300mm ƒ/4 telephotos from Canon, Nikon and Pentax outperform zooms that include 300mm, both in sharpness and AF speed.