Getting a good portrait lens is not difficult, but knowing which ones qualify is important. Before you go out and make a purchase, you should take a look into your camera bag to see if you may have a Canon portrait lens in there cleverly disguised as.. let's say a Macro lens or maybe a sports action lens.
The first issue is to determine what the qualifications of a good Canon portrait lens actually are. But in the process, keep in mind that you want to save money.
I hope this does not burst your bubble. I mean, photographers are kind of like fishermen and golfers. We are always under the impression that we need the next new camera or lens that comes out. Or, like my mother-in-law used to say, "If you don't have it, you need it." While the grass may be greener on the other side of the fence where your neighbor has a Canon EF 135mm f/2.0 portrait lens that she paid 00 for, it's possible that you can get by with something that you either already own or that costs just a tad bit less.
OK, real quick, the qualifications:
1. Image quality - this has to be really good. You do not want a lens that has poor image quality. After all, you will be shooting people, and most people are very vain about their appearance. It's not like taking a picture of a monkey or bear at the zoo. Those animals don't care what their picture looks like.
To find out whether the lens in question will qualify as a Canon portrait lens with respect to image quality, check some expert sites. But keep in mind that these guys are going to be very technical. You might just want to go to the Amazon or B & H Photo website and check user reviews. In that case, look for reviews from advanced amateurs or professionals. They will also be fairly reliable.
2. Focal length - Portraits can be taken with a lens that is as short as 50mm or as long as 300mm. Some of the pros use the extra long length to get the great bokeh, but normal portrait shooters use a lens of about 85mm to 135mm. The good news is that if you have an entry-level or mid-level digital SLR, you have what is known as a crop factor, which simply means that your camera multiplies the focal length of the lens by either 1.5 or 1.6 depending on the make of the camera. So if you have a 100mm lens, multiply it by the crop factor of, say 1.6, and you have an effective focal length of 160mm. And a 50mm lens becomes an effective focal length of 85mm. Of course, the shorter the focal length, the closer you will be to your subject. That's why a wide angle lens of 28mm will not be your best bet for a portrait lens.
3. Aperture - The aperture is really important. The wider the aperture, the better your chances for getting the nice blurry background that is desirable in this type of photography. You want a minimum of f/4.0 for longer length lenses, such as a 180mm lens, and at least an f/2.8 for the shorter lenses, such as 50mm. The larger the aperture, the better your background will be. But you also need a good sharp focus on the eyes because there is a very shallow depth of field with the wider apertures.
Generally, single focal length lenses are preferred for portraits, but that is not a hard and fast rule. Some photographers use their Canon 70-200 mm lens for this and are very happy with it.
OK, so there is a wide range of possibilities here. Going back to the first suggestion, look into your camera bag and see which, if any, of your current lenses fit the qualifications. If you still need to purchase a Canon portrait lens, proceed with patience. Getting a lens that can do two or three types of images is also a viable option.
One last thing. Third party lenses, like Sigma, Tamron, and Tokina are also great ways to save a few bucks. There are some excellent lenses made by these manufacturers, but make sure you check what the experts and others who have used them say in forums and online comment areas.
