Choice of lens for the portrait.
For tight head close up zoom lens is a must. But for head and shoulder portrait you can still use standard lens which has finer glass elements and will give the picture superb look.
Especially i have found that after sun goes down if u change iso speed to 200 to 400 depending upon luminosity of the environment your standard lens can give u excellent pictures with fine color in low light.
I am in love with 50mm perhaps the cheapest and the fastest lens in the world which is when rightly use in low light with large aperture can give stunning pictures with fine detail.