amehta wrote:
The key to doing portrait photography is figuring out your style and tastes. A part of how you create your style will depend on the equipment, but the equipment should follow the style, not the other way around. Since you asked about lenses, there are two major aspects of the style which can be expressed differently by different lenses: perspective and depth of field (DoF).
When taking a full-body shot, we're making a 2-dimensional, 1 inch image of a 3 dimensional, 6 foot person. If the focal length is short, you need to be fairly close to fill the frame with the person, and angle between the head and the foot is quite apparent, giving a sense of curvature. If the focal length is long, the subject will be much further away, the angle between the head and foot is much smaller, so the image looks flatter. The same effect happens with closer portraits, though smaller, but it's more apparent because we notice this in the face more than in the whole body.
The depth of field is about what is visibly in focus and what is not in focus. Some portrait shooters like things in front of and behind the subject in focus so they can include things which help define the subject. If you're doing a portrait of an athlete, for example, shooting on their field or court could give context for what is important to the person. Having more of the area in focus is good, because it is integral to the portrait. This is a "deep" DoF. Alternatively, the portrait could be all about the person, with the setting secondary, so you want it out of focus, since the viewer's attention is drawn to things in focus. This can be done with a "shallow" DoF. One pro photographer friend described this as "incorporate vs isolate". There is no right or wrong on this, it's about your style.
To the question of which lens to use, let's say you're using the Canon 5D Mark III, and you want to take a full body standing shot of someone which fills the frame. The if we then pick a focal length for the lens, the distance to the subject is set. With these factors, perspective is simple: a shorter focal length has more sense of curvature, a longer focal length is flatter. Meanwhile, DoF depends on two more things: the focal length and the aperture, but the dependence is not simple. With a longer focal length, the DoF is also longer, and a smaller aperture (f/8 instead of f/4), the DoF is deeper.
To the question of specific lens choices, the main question is whether you want a shallow DoF? One thing associated with DoF is bokeh, the character of what is out of focus. It can be smooth and creamy or harsh and distracting. This isn't a big factor for deep DoF since everything is supposed to be in focus anyway. For shallow DoF, however, the prime lens has two advantages: for comparable level lenses, the prime will tend to have a larger maximum aperture, and their design can concentrate on good bokeh. Meanwhile, zooms offer a lot more versatility.
If you want to isolate your subjects, consider primes. If you want to include the environment in the portraits, zooms are an easy choice.
The key to doing portrait photography is figuring ... (
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An excellent dissertation Anand ... you are very knowledgable!
Your namesake.