There are very few lenses that cannot be used as portrait lenses. Lenses with focal lengths ranging from 14mm through 800mm can be used to capture the world's most valuable (but not always the most cooperative) subject - people. Still, not all lenses are good choices for all portrait situations, and some lenses truly excel for portrait photography.
The first portrait photography concept you need to be aware of is perspective. If you move in too close to your subject, the part of their body closest to the lens is going to appear drastically enlarged relative to the rest of their body - due to the perspective. That body part is usually the nose - and few people want their nose enlarged - and doing so can make them uncooperative. The subject may also be uncomfortable with you in their personal space - an uncomfortable subject will not likely photograph well.
The converse is also true. If you are too far away from your subject, their features become compressed in appearance. I find this look far more attractive than the big nose look and often prefer to use longer focal lengths for my people subjects, but be aware of what is happening in your images. Being too far from your subject makes communication difficult. Physical obstacles (such as a wall) can also inhibit the use of longer focal length lenses.
The portrait lens focal length decision should be based on the perspective you want, the subject framing desired and the working space available. A wide angle lens makes the most sense when used for environmental portraits - where your subject is in the environment they are to be photographed with - such as a workplace. And conversely, a long telephoto lens should be used for a tight head shot - to keep the nose nicely-sized.
Conventional teaching is that the 85-135mm focal length range is ideal for portrait photography (field of view crop factor included). I generally agree with this teaching, though I will often use wider focal lengths - such as 50mm for full body portraits or 24mm for large group pictures. And I prefer a longer focal length for tightly-framed portraits - such as head shots.
A blurred background will make your portrait subjects pop. Longer focal length lenses will make blurring away a distracting background easier, as will wide apertures. The wide apertures will of course reduce depth of field. The right balance of depth of field and background blur must be achieved - the mouth & both eyes in focus is often my minimum standard.
Are you shooting in a studio with a special background (such as rolled paper) and using studio strobes? You will probably be using narrow apertures such as f/8 or f/11. In this scenario, your lens choices increase dramatically. Most decent lenses in the focal length you need will perform reasonably well for you.
The sample portrait included at the top of this page was captured with an 85mm focal length and an f/1.4 aperture using a full frame body. The background is almost completely melted away while a pleasing perspective has been captured.
With that background, let's get to some recommendations.
The Best Canon Portrait Lenses - My Recommendations
My Favorite Portrait Lens
The 70-200 f/2.8 L II IS Lens is the best zoom lens I've ever used. This completely professional grade lens has incredible image quality, fast and accurate AF and a late-generation image stabilization system in a solid, weather-sealed, fixed-size body. The wide-as-it-gets-in-a-zoom-lens f/2.8 max aperture over the entire focal length range allows the background to be blurred away and delivers a great bokeh (background blur quality). This is one of my most-used lenses - I would be lost without it - especially for portrait shoots.
My Other Favorite Portrait Lens
The shallow depth of field look that an 85mm focal length and an f/1.2 aperture delivers will set your portraits apart. While I typically use multiple lenses in a shoot, I can shoot entire portrait sessions using this lens alone. Photos taken with this lens usually end up in the selects pile even when other lens captures are included as options.
This lens does not have the fastest AF and the electronic manual focusing is not my favorite. I rarely use MF when shooting portraits, but must be careful to not accidentally adjust focus manually as this is easy to do with this lens. To prevent accidental manual focusing after autofocusing, I disable electronic manual focusing in camera - when using cameras supporting this feature. This is an L lens with the build quality you would expect from such. Chunky with some heft is how I would describe the feel of the 85 L II.
A less expensive alternative to this lens is the Sigma 85mm f/1.4 EX DG HSM Lens. The sample portrait at the top of this page was shot with this lens. I really like the Sigma, but my hesitancy to give the Sigma 85 a full blown recommendation is due to the less-accurate AF. Plan to shoot extra images to cover this inaccuracy issue if opting for the Sigma.
Excellent Image Quality from a High-Performance Lens
The 24-70 L II leaves little to be desired - except perhaps image stabilization - and perhaps a lower price. Expect sharp images, very fast & accurate autofocus along with nice build quality including weather sealing. This lens is an exceptional choice for your wider-than-head-shot portraits, including environmental portraits through head & shoulder portraits.
Light Weight, Impressive Image Quality, Fast/Accurate AF, Image Stabilization, Excellent Value
Yes, it is a macro lens - that feature is a bonus. The 100mm focal length works very well for portraits - and it works well for tight portraits on an APS-C body. The image quality from this lens at any focus distance is very impressive. An f/2.8 aperture will create a nice background blur and image stabilization will help you capture sharp images even when you are tired - though the weight of this lens will not be a big contributor to that tiredness.
Impressive Lens in All Regards
The 200mm focal length requires some working distance for portraits (especially on an APS-C/1.6x body), but the look that this lens delivers at f/2 is very impressive. Also impressive is this lens' AF performance, image quality, build quality and image stabilization. Perhaps equalizing all of this impressiveness is the size, weight and price of this lens. This lens will work double duty as an excellent indoor action lens.
Wide f/2 Aperture, L Lens Build Quality & Performance
The 135mm focal length is still a slightly long focal length for a general purpose portrait lens, but this lens is dramatically smaller, lighter and less expensive than the 200 f/2 IS. And it will produce memorable portraits. Though this is one of Canon's older (but still current) lenses, it performs very well in all regards. Again, this lens will work double duty as an indoor action lens.
Impressive Image Quality, Great Build Quality, Fast AF, Image Stabilization, Compact & Light, Great Value
If you don't need the 70-200 f/2.8 L II IS Lens' f/2.8 max aperture, the 70-200 f/4 L IS will give you everything else in a smaller, lighter and less expensive package. Without the f/2.8 aperture, you will need twice as much light to stop subject motion (at f/4) - and you will not be able to create a background as diffusely blurred. But, you also give up a substantial amount of size (still fixed) and weight - and your wallet will remain heavier. You give up very little in image quality or other pro-grade features including solid, weather-sealed build quality.
Incredible f/1.2 Aperture, Great Build Quality, Nice Size
The 50mm focal length falls below the classic 85-135mm range, but it still has great value for portraits - especially mid-to-full body portraits. And when used on an APS-C body, the field of view closely approaches the 85mm bottom of that range. This is a pricey lens and it is not tack sharp at its widest aperture, but the look of 50mm f/1.2 in portraiture is very sweet.
Canon IS "II" big white telephoto lenses are all spectacular and perform especially well in action scenarios. One of the wider focal length versions of these lenses is the 300mm f/2.8 L IS II. 300mm is relatively long focal length for portraits, but the images this lens delivers completely rock. You will probably find this lens best used outdoors or in a large public venue.
10. (APS-C Only) Canon EF-S 17-55mm f/2.8 IS USM Lens
Wide Aperture, Great Image Quality, Fast Ring USM AF, Image Stabilization
Framing like a 27.2-88mm lens on a full frame DSLR, the excellent 17-55mm f/2.8 makes a very good portrait lens on an APS-C format (only) body. The 88mm angle of view is not long enough for tight head shots, but the rest of your portrait framing needs should be covered. The image quality from this zoom lens is very good as is the AF performance. Image stabilization is icing on the cake. The EF-S 17-55mm IS Lens is one of the ultimate general purposes lenses.
Great All-Around Lens, Good Value
The 24-105 L is one of my favorite general purpose lenses, but it also works well for portraits. I would stay back slightly farther than tight head-shot framing distance with this lens on a full frame camera, but there is plenty of portrait usage remaining in this lens. The f/4 aperture is not going to create background blur as strong as the wider aperture options.
The Best Affordable Canon Portrait Lenses - My Recommendations
Excellent Value, Very Good Image Quality, Pro-Grade Build Quality, Fast AF
The 70-200 f/4 has an entry level price, but its performance is completely pro grade. It has a solid range of portrait focal lengths with image quality that will please. For its quality level, this is a rather compact/light, fixed-size telephoto zoom lens with great multi-purpose utility.
Just a Nice Lens
The Canon 85 f/1.8 is a nicely-priced, wide aperture compact prime lens with very good image quality and fast autofocus.
Another Nice Lens
Basically, the 100mm f/2 is the same as the 85mm f/1.8. Add 15mm and reduce the max aperture 1/3 stop. Both are nice lenses.
Extremely Sharp, Fast & Accurate AF, Great Value
The 100mm macro delivers exceptional image quality - especially for the price. This lens will give you great portrait perspective and adds macro capabilities as a bonus.
Low Price, Small Size, Light Weight, Impressive f/2.8 Image Quality
While this lens is not sharp at f/1.4, it is razor sharp at f/2.8 - which is still a rather wide aperture. This price, size and weight of this lens are all very attractive attributes. Build quality and AF speed are not.
Visit the Canon Lenses page for more recommendations.