i have AF NIKKOR 35-70 MM 1:3.3-4.5 and NIKON DX AF-S NIKKOR 18-135 1:3.5-5.6G ED
You are fine with what you have.
With the Nikon 18-140 (the 18-135 is a Canon lens), you are set up for everything from a large family/group portrait, to a TIGHT head shot.
That is the lens that I use.
Here is the other angle that I hinted above.
WHAT is YOUR definition of a portrait picture?
The reason is this affects the lens choice:
- Single person
- - A TIGHT head shot
- - A head and shoulder shot.
- - A waist up shot.
- - A 3/4 length shot.
- - A full length shot.
- A 2nd person in the shot/couple shot
- - Head and shoulder
- - Waist up
- - 3/4 length
- - Full length
- Multi-person/family pic
etc. etc. etc.
There is NO
ONE definition of a portrait.
The closest is the traditional head and shoulder shot.
But what about a wedding couple's shot, isn't that also a portrait? What about your daughter at her piano, that is an environmental portait. See what I mean.
The next factor is the distance from the camera to the subject.
Example1, I do not have the space of the old traditional portrait studio, so I cannot back up as far. So for a full length or group pic, I would have to use a wider lens than if I had more space. I've shot indoor group pics where my back was literally up against the wall, I could NOT back up any further.
Example2. If you are shooting an "environmental portrait," such as your daughter at her piano, you may be even more space constrained, and have to go to a wider lens, or a tighter composition.
Each of the above shots call for a different lens, to capture the desired image.
Today a zoom (or two) is often used rather than a set of prime lenses, that was used in the past.
- In the FX world, it would probably be the 24-70/2.8 + 70-200/2.8, or Tamron 35-150
- in the DX world, it would be the 16-80/2.8-4, or similar (18-70, 18-105, 18-140).
Now, as for primes:
The 50/1.8 is often advertised as a DX portrait lens. But if you look at that list of shots above, and compare the 50 to a 16-80 zoom, you will see that it is a rather limited lens.
The 50 on a DX camera is equivalent to a 75 on a FX camera, and this is shorter than the film era portrait lens, the 105/2.5.
Back in the film days, the Nikon 105/2.5 was considered "the" portrait lens for Nikon 35mm camera.
But like the 50/1.8 on a DX camera, it is limited to only a few of the shots in the list.
IF that is primarily what you shoot, then a prime of the appropriate focal length is fine.
But if you are like most of us, shooting everything from head and shoulders to full length, a zoom is more practical.