Here are some of the most popular lenses around:
This is one of Canon's least expensive lenses, which is why it is so popular. It's wide open, fast, f/1.8 aperture is handy for utilizing the selective focus technique because of the very shallow depth-of-field (DOF) the lens can produce. The wide aperture is also useful when you don't have a lot of light available. Sharpest focus is obtained by using intermediate apertures, f/4 to about f/11.
Care must be taken with shallow DOF though because the DOF can get very thin, and you have to remember that the plane of focus is always parallel to the plane of the image sensor. If you want both of someone's eyes in focus in a portrait,
both eyes will need to be on a plane parallel to the image sensor.
This lens only has 5 aperture blades, and the cost of the lens is directly related to it's build quality and durability.
Nikon also has an inexpensive f/1.8, 50 mm lens. Nikon's lens has 7 aperture blades, giving a fairly smooth, somewhat creamy look to the shallow DOF blur the lens is capable of producing.
Since it is an AF lens it does not have an auto focus motor in the lens like Nikon's AF-S lenses do. It is a CPU lens though, and it sends focus information to all Nikon camera bodies so the camera can turn on the viewfinder's in-focus indicator when the lens is manually focused and focus has been achieved at the selected viewfinder focus point.
Both of these inexpensive 50 mm f/1.8 lenses are popular for doing portrait type photographs when room to back up from your subject is at a premium, and as mentioned above they can produce very shallow DOF for selective focus techniques. That can cause focus issues if one isn't familiar with some of the technical nuances of DOF and how to use these standard focal length lenses effectively.
Longer focal lengths are more effectively used for portrait type photographs, when space permits.
Many beginner digital SLR users decide they would like to have some additional 'reach' beyond the typical 18-55 mm most kit lenses provide. Reach means zooming in more, making things seem closer, or more magnification.
This is Nikon's AF-S DX 55-200 mm f/4-5.6G VR (Vibration Reduction) lens, and it is one of Nikon's best lens values when you consider that Nikon's pro grade AF-S 70-200 mm f/2.8G VR II lens costs $2200 or more.
This lens is more compact and much lighter in weight than the pro 70-200 mm version, making it much more of a walk-around, keep it on the camera most of the time kind of lens.
The VR (vibration reduction) is very handy because it compensates for camera shake to produce sharper, clearer pictures in unsteady or poorly-lit conditions.
Canon also has a lens in this focal length, and price range, the EF-S 55-200 mm f/4.0-5.6 IS.
Canon calls the system they developed to compensate for camera shake and to produce sharper, clearer pictures in unsteady or poorly-lit conditions, IS, for Image Stabilization.
Like Nikon, Canon also makes a much higher priced EF 70-200 mm professional level lens, so this EF-S Canon version is also a good lens value.
You may want to note that Canon EF-S lenses cannot be used on Canon's higher end EF cameras. Canon's EF only cameras are not beginner digital SLR cameras in any event.
Next in out lineup of popular lenses are the superzoom, 18-200 mm lenses . This lens focal range is very popular, and is considered a very handy 'walk-around' lens because of it's convenient focal length range.
The 18-200 focal length range is like having 2 lenses, an 18-55mmm and a 55-200 mm, in one, but without having to actually carry, and change, between two lenses.
The Nikon 18-200 mm also looks really good on your Nikon camera because it is somewhat bigger around than a 55-200 mm lens.
There are 3rd party lens makers like Sigma and Tamron that also make superzoom lenses for both Nikon, Canon, Pentax, and Sony digital SLR cameras.
Next on our lens hit parade are the longer reach 55-300 mm lenses. These lenses appeal to nature and sports photographers. The additional 100 mm of focal length can be quite handy.
With longer focal lengths Image Stabilization and/or Vibration Reduction become even more important since any extraneous camera movement can negatively affect getting sharply focused photographs.
Since most digital SLR camera owners camera's have a crop image sensor lens focal lengths have a 1.5, 1.6 or 2.0 focal length multiplier applied to the field-of-view (FOV) any lens provides, the FOV a 300 mm lens provides is equivelent to 450 to 600 mm.
At a later date I'll cover some of the other lenses for more specific uses, like shooting landscapes, or action sports.