I am a portrait photographer and currently am using the 50mm Lens (1.8) for the Canon Rebel t5i. I want to excel in my photography (quality wise) I've been researching about other lenses but Im still unsure as to which lens I should purchase next. I don't want to spend a ridiculous amount on money for a lens that doesn't specialize in what I photograph. What lens do you recommend I get next?
As to focal length lens used for portraits: The most common error made by inexperienced portrait photosphers is working in too close. Things close to the lens reproduce large and things far from the camera reproduce small. We are talking perspective. If the photographer works in too close, the nose is reproduced too large and the ears too small. This is not a focal length thing; it’s a camera to subject distance thing.
It’s an easy thing to mitigate but human nature abhors leaving empty space around our subject, so we move in and fill the viewfinder. To avoid this Catch-22, best to use a longer that “normal” lens. The lens of choice is a moderate telephoto.
First you need to know what a “normal” lens is. For the full frame (Fx) the image area measures 24mm height by 36mm length. This format, when fitted with a lens about equal to the diagonal measure of the format, delivers a “normal” view. This is a view that captures the human perspective. For the Fx, this a lens about 45mm, however this value by tradition is rounded up to 50mm. A shorter is lens is said to be wide-angle, and a longer lens is considered a telephoto. For portraiture, experts agree, the ideal portrait range is 2 thru 2 ½ times “normal”. That works out to 90mm thru 110mm. Many portrait lenses were intentionally made 105mm.
Now the compact digital (Dx) format is 66% of the Fx (1 ÷ 1.5 crop factor x 100). The frame size averages 16mm height by 24mm length. The diagonal measure of this rectangle, and therefore the normal focal length for the Dx, is 30mm. The focal lengths that fit the portrait range are 60mm thru 75mm.
The 2 thru 2 ½ “normal” has a basis. By tradition, portraits are made large and hung on the wall or placed on the mantel. These must be enlargements as the Fx and Dx deliver minuscule images. The magnification used to produce a portrait will be 8x or more for the Fx and 12x or more for the Dx. The 2 thru 2.5 times the “normal” rule of thumb takes the enlargement factor into account making it unlikely that the finished portrait will display facial distortion (nose too big – ears too small).
Keep in mind that art has few rules, if any; you are free to follow your heart when selecting a portrait lens.