@shelley - For portraits you'll want a lens that's capable of obtaining an aperture between f/1.4 to f/2.8. Lower f-numbers produce a shallow depth of field (small area in focus) that allows you to capture isolated subjects against silky smooth backgrounds.
In addition to the need for low aperture's, you'll also want a lens that has a focal length between 50mm and 150mm. If you try to shoot portraits with a focal length wider than 50mm, you'll end up with features that just don't look right (large noses). If you shoot longer than 150mm, you'll end up with flat looking faces.
With those two necessary ingredients, my advice is to start with the Nikon 35mm f/1.8G. Both lenses are capable of obtaining an aperture of f/1.8 and their "effective" focal length falls into the ideal portrait focal range.
Now it may sound confusing, considering I recommended the 35mm lens and said the ideal focal length range is between 50mm and 150mm. Well, actually the 35mm lens has an effective focal length of 52mm when attached to the D3100.
The D3100 has a crop factor of 1.5x, which means the image sensor is smaller than that of a full frame DSLR (or film SLR). This difference in size results in a "crop factor". So any lens you attach to the D3100 will have to be multiplied by 1.5x in order to get the effective focal length.
Have I lost you yet? Ok, stay with me. :)
The "crop factor" is especially important when it comes to wide-angle (landscape) lenses, because the field of view isn't as wide when compared to full frame DSLR's (or film SLR's).
In regards to recommended landscape lenses, generally you'll want a lens with a focal length between 10-24mm to capture super wide views. Low aperture's aren't as important as they are for portraits. In fact, you'll end up using higher f-numbers in order to put the entire scene into focus.
Now before your jaw drops, I want to preface that wide-angle lenses can be fairly expensive. The Nikon 10-24mm f/3.5-4.6 (see here) is Nikon's "cheapest" wide-angle lens. If that price point is beyond your budget, then the next best option would be a comparable lens offered by Tamron (see here) or Sigma (see here).
The suggestion is that an L bracket is good for shifting from portriat to landscapes. This kind of accessory is quite useful for changing from horizontal to vertical, such as this:
Comments
In addition to the need for low aperture's, you'll also want a lens that has a focal length between 50mm and 150mm. If you try to shoot portraits with a focal length wider than 50mm, you'll end up with features that just don't look right (large noses). If you shoot longer than 150mm, you'll end up with flat looking faces.
With those two necessary ingredients, my advice is to start with the Nikon 35mm f/1.8G. Both lenses are capable of obtaining an aperture of f/1.8 and their "effective" focal length falls into the ideal portrait focal range.
Now it may sound confusing, considering I recommended the 35mm lens and said the ideal focal length range is between 50mm and 150mm. Well, actually the 35mm lens has an effective focal length of 52mm when attached to the D3100.
The D3100 has a crop factor of 1.5x, which means the image sensor is smaller than that of a full frame DSLR (or film SLR). This difference in size results in a "crop factor". So any lens you attach to the D3100 will have to be multiplied by 1.5x in order to get the effective focal length.
Have I lost you yet? Ok, stay with me. :)
The "crop factor" is especially important when it comes to wide-angle (landscape) lenses, because the field of view isn't as wide when compared to full frame DSLR's (or film SLR's).
In regards to recommended landscape lenses, generally you'll want a lens with a focal length between 10-24mm to capture super wide views. Low aperture's aren't as important as they are for portraits. In fact, you'll end up using higher f-numbers in order to put the entire scene into focus.
Now before your jaw drops, I want to preface that wide-angle lenses can be fairly expensive. The Nikon 10-24mm f/3.5-4.6 (see here) is Nikon's "cheapest" wide-angle lens. If that price point is beyond your budget, then the next best option would be a comparable lens offered by Tamron (see here) or Sigma (see here).
Hope that helps and happy shooting! :)
http://www.amazon.co.uk/FITTEST-Release-Bracket-Arca-Swiss-Compatible/dp/B00D3VSWA8/ref=sr_1_14?ie=UTF8&qid=1372844145&sr=8-14&keywords=l+plate+nikon