| The focal length of your lens is it’s main | | | | Now nobody says that you have to get a |
| characteristic. It determines your angle of view, | | | | ‘correct’ perspective, certainly I |
| that is, how close or how far away you have to | | | | don’t. But for some purposes it is more |
| be from your photographic subject to capture it | | | | important than others. If you’re taking a |
| in a certain size. With a short focal length | | | | close-up photo of someone’s face for |
| (wide-angle lens) you can stand close to | | | | instance, exaggerating the perspective and making |
| somebody and still capture their full body size. | | | | their nose look huge can do bad things for your |
| Opposite, with a long focal length (tele-photo lens) | | | | popularity. Again, determine the depth of the |
| you can stand far away from somebody and still | | | | visible parts of your subject, in case of a human |
| get a close-up picture. Briefly, the wide-angle | | | | face straight-on, it will usually be about 15-20 cm |
| lenses are considered good for landscapes and | | | | from the tip of the nose to the back of the ear. |
| photojournalism since you can capture the whole | | | | Then multiply by 10 and move back until you are |
| scene in the same shot and the long tele-photo | | | | at least 1.5-2 meters away and zoom in to fill the |
| lens is considered good for sport, wildlife and | | | | frame. Your focal length will typically be in the |
| paparazzi photography, since you can be relatively | | | | area of 100 mm which is incidentally referred to |
| far away from your subject, ideal if you | | | | as a portrait lens. |
| don’t want to disturb it or be noticed. The | | | | In case of big landscapes, long streets etc. it is |
| range of lenses and focal lengths available is listed | | | | impossible to be 10 times further away from it |
| here: | | | | than the total depth of the entire scene. To |
| Fish-eye lenses: 8-14 mm | | | | capture such scenes from close to far away, |
| Ultra wide-angle lenses: 15-20 mm | | | | you’ll normally need a wide-angle lens and the |
| Wide-angle lenses: 20-40 mm | | | | perspective will as a result be |
| Normal lenses: 40-60 mm | | | | ‘exaggerated’. This has a charm of |
| Portrait lenses: 80-100 mm | | | | it’s own though. It can result in a nice sense |
| Moderate tele-photo lenses: 90-150 mm | | | | of depth in the photo. |
| Tele-photo lenses: 150-300 mm | | | | With a long tele-photo lens your perspective will |
| Extreme tele-photo lenses: 300-1000 mm | | | | often become flat since you’ll be a bit far |
| Note: The focal lengths given here are by the | | | | away and the relative distances from you to the |
| “35mm equivalent” scale. Modern | | | | subject and the background are not that much |
| pocket-size digital cameras use a different scale | | | | different. And thus, the ‘flat’ perspective |
| and you might see something like “focal length | | | | arises because the background objects aren’t |
| 2.8-9 mm” on one of these. This does not | | | | rendered that much smaller than objects a little |
| mean that everything is taken with an extreme | | | | closer to you. |
| wide-angle / fish-eye look. Refer to your camera | | | | Now about the depth of field that the lens |
| manual to see how it converts into the 35 mm | | | | provides, as I said before, strictly speaking it |
| equivalent. | | | | doesn’t depend on the lens focal length. But |
| Now the question is, what focal length is good to | | | | for practical purposes, it does! When you zoom in |
| use and in which circumstances? | | | | on something, making your focal length longer, |
| It is often said that the fish-eye and wide-angle | | | | you magnify that part of your image more and |
| lenses provide an exaggerated perspective and a | | | | more, thereby increasing what’s known as |
| large depth of field (depth of focus). Strictly | | | | ‘the circle of confusion’. It is exactly |
| speaking though, this is not true since the | | | | equivalent to cropping your short focal length |
| perspective only depends on where you stand in | | | | photo and thus, since it's basically the same |
| relation to your subject and the depth of field | | | | image, it has the exact same depth of field. |
| only depends on what lens aperture you are using. | | | | Confused? Don’t let it keep you awake at |
| But these truisms, technically incorrect perhaps, | | | | night. When you look through your camera |
| are there for a reason. The thing about the | | | | viewfinder or at the LCD screen on the back of |
| exaggerated perspective comes about since, with | | | | it, you’ll see what’s in focus and what |
| a wide-angle lens you’ll normally go closer to | | | | isn’t. |
| your subject in order to fill your frame. Taking a | | | | A more important thing to be aware of is that |
| picture of a rose, for instance, with a 20 mm lens | | | | when you zoom in and use a long focal length, it |
| you’ll need to be within one foot distance in | | | | gets more important to keep your camera |
| order to render it in a decent size on your print. | | | | steady. A tripod is best, but it can be a bother to |
| With a 200 mm lens however, you’ll normally | | | | log around with all day long. Instead, try to look |
| take a few steps back, thereby changing your | | | | around you and see if you can put your camera |
| perspective. So while the perspective strictly | | | | down on a table or a stone somewhere, making it |
| speaking isn’t determined by the lens itself, | | | | rock steady. If not, at least try to steady |
| for practical purposes it is. | | | | yourself by leaning slightly against a tree or |
| In order to avoid the ‘exaggerated | | | | something. And use a quick shutter speed. If you |
| perspective’ there is a good rule of thumb | | | | are using a focal length of, say, 300 mm, then |
| saying that you should be at a distance of at | | | | use a shutter speed of no more than 1/300th of |
| least 10 times the depth of your subject. Things | | | | a second. You might want to make it even less, |
| like the size of your final print and the intended | | | | perhaps 1/500th of a second to be sure not to |
| viewing distance also plays a role, but for | | | | let that shaky hand of yours blur the picture. |
| simplicity’s sake let’s just follow the rule | | | | Even slight hand-shaking from your pulse can blur |
| of thumb: If the rose is 10 cm across, you’ll | | | | your image when using long lenses, so be sure to |
| have to be at least 100 cm (1 meter) away from | | | | follow this rule of thumb. Some modern |
| it to avoid exaggerating the perspective. Once | | | | tele-photo lenses have a stabilization mechanism |
| you’ve decided on your distance and | | | | build into them, and this can greatly reduce |
| viewpoint, just zoom your lens to the focal length | | | | hand-shake on the lens, allowing shutter speeds to |
| that fills the frame with a nice composition. | | | | be 4 to 8 times longer. |