Understanding camera lenses to more creative (PART.1)

By Rephopy Mar 14, 2010 0 comments
Understanding camera lenses can help add more creative control to digital photography. Choosing the right lens for the task can become a complex trade-offs between cost, size, weight, lens speed and image quality. This tutorial aims to improve understanding by providing an overview introduction to concepts related to image quality, focal length, perspective, prime vs. zoom lens and the aperture or f-number.


All but the simplest cameras contain lenses which actually consists of several "lens elements." Each element of directing the path of light rays to create images as accurately as possible on a digital sensor. The goal is to minimize the aberrations, while still utilizing the elements of the least and most expensive.

Optical distortion occurs when the dots in the image does not translate back to a single point after passing through the lens - causing blurred images, the contrast is reduced or misalignment of the color (chromatic aberration). The lens may also suffer equally, radially reducing image brightness (vignetting) or distortion. Move your mouse over each option below to see how this can affect image quality in extreme cases:

Each of the above problems are present to some degree with any lens. In the remainder of this tutorial, when the lens is referred to as having a lower optical quality than other lenses, this is expressed as a combination of some of the artifacts at the top. Some artifacts may not be approved lens of others, depending on the subject.


Lens focal length determines the angle of view, and thus also how much the subject will be enlarged to a certain photographic positions. Wide angle lenses have short focal lengths, while telephoto lens has a focal length longer be appropriate.

Many people would say that the focal length also determines the perspective of an image, but strictly speaking a change of perspective, with only one location relative to their subject. If someone tries to fill the frame with the same subjects using both wide angle and telephoto lens, the perspective is changed, because one is forced to move closer or further away from their subjects. For this scenario only, wide-angle lens exaggerates or stretches perspective, while telephoto lenses compress or flatten perspective.

Perspective control can be a powerful tool in photographic composition, and often determines one's choice in focal length (when a person can shoot from any position). Move your mouse over the image above to see the exaggerated perspective because a wider angle lens. Notice how the subject in the frame remains almost identical - and thus require a closer position to a wider angle lens. The relative size of the object changes that are much smaller door to be relatively light nearby.

Other factors can also be affected by lens focal length. Telephoto lenses are more susceptible to camera shake due to the small hand movements become magnified, similar to the experience shakiness when trying to see through binoculars. Wide-angle lenses are generally more resistant to flare, partly because the designers thought that the sun is more likely to be in the frame. Final consideration is that the media and a telephoto lens generally produce better optical quality for the same price range.


The focal length lens may also have a significant impact on how easy it is to achieve a sharp handheld pictures. Longer focal lengths require shorter time to minimize exposure to blurring caused by shaky hands. Think of this as if someone tries to hold the laser pointer is stable; when the pointer is shining bright spot on a nearby object that usually jumps around less than for more distant objects.

This is mainly due to the rotational vibration very little magnified by distance, whereas if only the top and bottom or side to side vibration is present, the point of the laser light will not change with distance.

A general rule of thumb for estimating how fast the exposure necessary for a given focal length is one of the focal length rule. It states that for a 35 mm camera, the exposure time needs at least as fast as one of the focal length in seconds. In other words, when using a focal length of 200 mm on a 35mm camera, the exposure time needs at least 1 / 200 sec - if vague it may be difficult to avoid. See the tutorial on reducing camera shake by hand-held photo for more on this topic.

Keep in mind that this rule only for a rough guide, some may be able to hold his hand shot for times longer or shorter. For users of digital cameras with cropped sensors, one needs to convert into the equivalent focal length 35 mm. Sharing is sexy

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