For cropped frame sensor cameras, what lens would work best for taking portraits close to the face? If the focal length is approximately 2 ft between the subject and the camera, what lens would work best for these portraits?
Art has few rules. You are free to work the human face from a distance of 2 feet. If you do, the nose will image too large and the ears too small. We are talking facial distortion that will result in images that are unflattering. That’s OK if you truly want to induce facial distortion.
The “normal” lens for the compact digital is 30mm. If distortion is your goal accentuated by working in close, then choose a 30mm. To intensify the distortion, use a shorter lens as this delivers a wide-angle view.
If classic portraiture is your goal, you would be wise to mount a moderate telephoto. Such a lash-up will force you to step back and this act will mitigate facial distortion. Best would be a focal length 2X thru 2.5 X “normal”. Now we are talking 60mm thru 80mm. Stepping back and using this focal length range will deliver portraits that flatter.
To pick a good lens, there are a couple things you want to consider.
The first thing that you want to check is the minimum focal distance. Some lenses (for example) can only focus at distances of more than 1.5 meters.
Second, you need to think about focal length. Shorter focal lengths tend to give more distortion.
A favorite among photographers (for cost and quality) is the "nifty fifty lens"; a 50mm f/1.8 lens. Canon and Nikon both have an equivalent for relatively low cost, the results are better than anything you can get for the cost, and the low f/stop number allows for a great artistic feel.
If cost is not an issue, there are many other lenses that work great. The best focal range for portraits (this is subjective) is between 50mm and 150mm. Those provide good results.
Hope this helps.