Does a Canon 18-135mm have a wider field of view than a Canon 24mm?

A 18 thru 135mm zoom is the focal length Canon markets as an entry level lens for its line of APS-C format cameras. This format is the digital counterpart of the film camera system known as the Advanced Photo System – Classic format. The sensor (film size is 66% of that of a full frame 35mm format. Don’t be upset by the fact that this format is smaller than the full frame which is 24mm height by 36mm length. Your camera’s image sensor is 15.1mm height by 22.7mm length.

We fit lenses base on need keyed off by corner to corner (diagonal measure) of film or digital sensor. If we mount a lens with a focal length that is equal to the diagonal measure, the angle of view obtained is approximately 45°, camera held in the horizontal (landscape position). Such a lash-up is said to deliver a “normal” angle of view, some say it replicates the perspective we think is “normal”. The diagonal measure of your camera is 27 ¼ mm. Zoom to about this focal length and you have set your camera to “normal”. OK to round this value up to 30mm and call it your normal.

If you zoom twice normal = 60mm, you enter into the realm of telephoto. When set to 60mm your camera images objects double size. Based on 30mm being “normal”, mount 8 x 30 = 240mm lens, your view is approximately the same if you were viewing with 8x binocular. Likely you have discovered that when you do a head shot and the camera is too close, facial distortion creeps in. The nose reproduces too large for the ears. The solution is simply to step back. For portraits we use as zoom setting of 60 – 75mm. This forces us to step back.

Wide-angle starts at 70% of “normal” = 20mm = 60° angle of view Zoom to 18mm lens delivers 64 ½ ° angle of view Mount a 24mm and the angle of view is 50 ½°

Hope this helps!

If you are getting an APS-C camera, the 18mm setting of the 18-135mm will indeed be wider than the 24mm.

A 24mm prime that is full frame capable and used on a full frame camera, however, will be wider than either on APS-C, and wider than an 18mm used on a full frame camera that has been configured to only use an APS-C sized section of the sensor (as would happen if you were to use the 18-135mm on a full frame camera).

Lenses are often discussed using their "35mm equivalent", that means the effective focal length on a 35mm film or full frame camera.

The 35mm equivalents for these lenses are:

18mm on APS-C: 28mm* - the shorter of the two focal length considered "standard" wide angles.

24mm on APS-C: 35mm* - the longer, less wide of these two. Used by some as a "wide normal" since the perspective still looks very natural.

24mm on full frame: 24mm - considered a STRONG, but not yet extreme, wide angle - there will be pronounced visual effects due to a perspective that is markedly different from a human eye.

However, we all have gotten very used to wide angle perspectives these days due to cell phones - these tend to have 22mm to 26mm equivalent focal lengths installed. If you want to have a strong impact from wide angle perspectives in your images, indeed consider going even shorter (=wider). This gets you into so called "ultrawide" or "extreme wideangle" lenses though (20mm equivalent and below), which require some care to use - anything that is not either precisely aligned/level or intentionally shot to make good use of the perspective distortion will just look warped and sloppy.

Be aware that short focal lengths come in two basic types: "rectilinear" and "fisheye". You want "rectilinear" unless you know you don't.

*rounded to the closest "well known" focal lengths.