Perspective

One of the most interesting features of wide-angle lens is "the capability to stretch perspective". What do I mean by that? I mean that when you look through a wide-angle lens, it seems that the distance between objects has extended. The objects that were not so distant could appear too far away. And the proportion of objects dramatically increases, so the one that close to the camera look enormous, but those, which are father away almost disappear in the distance.
But there is a quirk - it's not a physical thing, but an impression we get. As one of the readers (signed as FL) has noted (and thanks for that):
The connection between focal length and perspective in your explanation is false. The only thing you have done is choosing an arbitrary position in space that the three lines are to intercept at. If this position is not the same position as the camera, it only shows that you have moved. And that is exactly what has changed the perspective, you moving, not the change in focal length. Change in focal length without moving does nothing to the perspective. Moving does a lot to the perspective, also when keeping the same focal length. Perspective and moving is strongly related. Perspective and focal length is not related in any way (other than you might have to move in order to get your arbitrary position inside the frame, which in turn will change perspective).

Viewing angle on the other hand, is related to focal length, but a larger/smaller viewing angle will not change the perspective, not even a bit. Try drawing all three lines from the same point on the base line (where the camera sits) and see for yourself that the perspective does not change, only the viewing angle. Or even better, do this test: Take two pictures, from the same position without moving, one with say 28 mm focal lebngth, the other one with for example 100 mm. Crop the 28 mm image and resize it, so it has the same scale as the 100 mm. Lay them ontop eachother, and voila: The perspective is the same, despite the different focal lengts. You can also google for "focal length perspective myth" and see some examples (for example this one ) without making your own experiment (but experimenting is much more fun). You will also discover, if you examine the pages returned by google, that the exact same thing goes for focal length and DOF (depth of field).
And I have to agree with this comment. In order for the object to fit entirely into the frame - we move and as such change the perspective. So the primary driver of the change is the viewing angle and the fact that we step back or forward to adjust what gets into the frame. Though the final effect and impression is still of the "stretching perspective", which is just an impression. So, when you read my words about "stretching perspective", keep in mind that this applies only to our impression (since we have moved to achieve the desired result).
The effect caused by various focal lengths on the perspective I described in one of the previous articles. But I will try to dive deeper and describe in more details here.
Here is the basic comparison of impression between different types of lenses:

Perspective Stretch
The image shows how different lenses affect the perspective. The wider the angle the shorter the stronger the difference in the sizes of the elements in the photograph. If you look at the point where the green line with the label "wide angle" intersects with the axis, this is a point, which I would call perceptive vanish point for wide angle lens. What do I mean by that? Well, theoretically at this point and beyond (at this distance from the focal plabe) all elements would be represented as a dot or not visible at all. For normal lens (of in reallity) this vanishing point is somewhat farter from the focal plane than for the wide-angle lens — the intersection of the blue line and the axis.
What do those two points mean? They mean that the wide angle lens reduce the actual distance to the vanishing point. Which results that our brain, when judging the distance and sizes of the objects in the photograph, assumes that the distance to the vanishing point is the same as with normal lens (i.e. reality). But this assumption makes it to stretch the perspective recorded in the image to the normal one. This stretch is indicated at the right bottom corner of the picture above with the red ink.

Zoom lenses

Why carry around a whole bag of fixed focal length ("prime") lenses when you could just buy a Tamron 28-300 zoom lens for less than $400? With a twist of a ring, the Tamron will give you any focal length from 28mm to 300mm. The only problem with this idea is that, sadly, the laws of physics and common sense have not been repealed.
Photographic lenses in general are not very good. They only appear to be good because people very seldom enlarge or closely inspect images. Camera lenses are subject to many kinds of distortion, all of which are more difficult to reduce in a zoom lens design. Furthermore, zoom lenses tend to be slower (admit less light) than prime lenses. This forces the photographer into using flash and/or a tripod.
Does that mean you shouldn't buy a zoom lens? Absolutely not. The average Canon EOS photographer will own three beautiful zoom lenses: Canon EF 16-35mm f/2.8L USM (review), Canon EF 24-70mm f/2.8L USM (review), Canon EF 70-200mm f/2.8L IS USM (review). These are a great convenience for the lazy and/or pressed-for-time photographer. However, none of these are as good as prime lenses in their focal length range. Each of these zooms costs over $1000, so they won't help you out if you don't like the prices of the prime lenses.
If you can only have one lens, the Canon EF 24-70mm f/2.8L USM is probably better than the Canon EF 50mm f/1.8 II, $93 (review). But the 50/1.8 is better than cheaper mid-range zooms.

Teleconverters

A teleconverter is a small lightweight intermediate optic that will increase the magnification of a lens, while reducing its effective aperture. So a 2X teleconverter turns a 300/2.8 into a 600/5.6. A lot of times new photographers ask me if they can save money by buying a teleconverter and sticking it onto their 28-70 zoom to get a 140mm lens. Sadly, good teleconverters cost $400 or $500 and they only work optically on expensive lenses. With a typical zoom lens, you'll get vignetting (darkening of the corners) when using a teleconverter.
Teleconverters are for professionals who own expensive lenses and want to save weight by not carrying two lenses. They are also useful sometimes with specialized tilt-shift lenses so that you don't have to buy these in lots of different focal lengths.

Telephoto Camera Lenses

Telephoto Camera Lenses

Telephoto lenses are high-magnification devices. These are for when you are photographing something from far away either because you want to flatten perspective or because you are unable to approach your subject.
It is difficult and expensive to produce a high-quality telephoto lens. In fact, only in the last couple of decades have manufacturers been able to design really high quality 300mm and longer camera lenses.
Telephoto lenses can be useful for portraits, most often in the 85-180mm range. Photography of large animals is facilitated by 300-600mm lenses. Photography of birds starts with a 600mm lens and goes up from there.
Telephoto camera lenses that serious Canon EOS photographers buy include the following:
• Canon EF 100mm f/2.8 Macro USM, $529 (review), capable of focusing down to 1:1, useful for both macro and portraits
• 85-135mm super-fast portrait lenses, e.g.,
◦ Canon EF 85mm f/1.8 USM, $380 (review)
◦ Canon EF 85mm f/1.2L II USM, $1999 (review)
◦ Canon EF 100mm f/2 USM, $435 (review)
◦ Canon EF 135mm f/2L USM, $999
• 180-200mm macro or portrait-only lens, e.g.,
◦ Canon EF 180mm f3.5L Macro USM, $1370 (review)
◦ Canon EF 200mm f/2.8L II USM, $769
• Canon EF 300mm f/4L IS USM, $1269 (review) + 1.4X teleconverter lightweight wildlife kit ($1,500)
• Canon EF 300mm f/2.8L IS USM, $4499 (review) + 1.4X teleconverter heavyweight wildlife kit ($5,000)
• Canon EF 600mm f/4L IS USM, $8050 (review) + 1.4X teleconverter bird photography kit ($10,000)
For the equivalents in the Nikon system, please see our Nikon System Explained page.

Wide angle camera lenses


With a full-frame digital SLR or 35mm film, a wide angle lens is generally considered anything with a focal length of 35mm or less.
Here are a couple of snapshots taken with an ancient Canon 20-35/2.8L zoom lens (replaced by Canon EF 16-35mm f/2.8L USM, $1520 (review)). Note that the image on the left, at 20, appears to be significantly distorted if you view it from far away. But try clicking on it so that you get a monitor-filling JPEG. Then move your face in close to the monitor so that you are viewing it from a few inches away. The distortion disappears, right? A wide angle lens does not distort perspective but, if the viewer of the ultimate image does not adjust his viewing position, it appears to do so.
As a practical matter, most people these days aren't impressed by a wide-angle effect until you get down to 24mm. Wide angle camera lenses start to get expensive at 20mm ($500) and wider. So good compromises these days are are probably a fixed 24 ($250) or a high-quality 16-35 zoom ($1500). See the Canon and Nikon system pages for an idea of what's available.

Canon EOS Digital SLR System

The Canon EOS system of digital single-lens reflex (SLR) bodies and lenses is the standard choice among professional photographers worldwide. This page makes it easy to shop for Canon digital bodies and EOS lenses. Every component manufactured by Canon is covered, plus a few exceptionally good third-party components. If you are new to photography, you might want to start with our article "Building a Digital SLR System".

This article goes through every section of the Canon EOS system and concludes with some starter system recommendations.


Canon Eos body


Small sensor bodies are good for telephoto work, such as wildlife photography. A 100mm telephoto lens that would be ideal for portraits on a film or full-frame sensor body gives a 150mm equivalent perspective on a small sensor ("APS-C") body. The full-frame sensor bodies are good for wide angle photography, low-light photography, and ultimate image quality.
EOS-1Ds Mark III EOS-1Ds Mark III
EOS-1D Mark IV EOS-1D Mark IV
EOS-1D Mark III EOS-1D Mark III
EOS 5D Mark II EOS 5D Mark II
EOS 7D EOS 7D Digital
EOS 50D EOS 50D Digital


Normal lens

A normal or standard lens is light in weight and approximates the perspective of the human eye. Normal lenses have large maximum apertures, indicated by small f-numbers such as f/1.4 or f/1.8, and thereby gather much more light than zoom lenses. It may be possible to take a photo with a normal lens in light only 1/8th or 1/16th as bright as would be required for the same photo with a consumer-priced zoom lens. Another advantage of the large maximum aperture is that the viewfinder will be correspondingly brighter and therefore easier to use in dim light. (SLRs keep the lens wide open for viewing and stop down to whatever aperture you have set just before taking the picture; this is why the viewfinder always looks the same even if you switch from f/1.4 to f/8 to f/16.)