Talking about about Today's Telephoto Technologies

Telephoto Lens Technology

The Telephoto lens technology is specifically engineered to deliver a big image of a remote subject in a camera system of somewhat short focal length. A telephoto lens typically contains of a positive set of lenses plus a negative set of lenses, separated by a substantial distance. The optical center of these types of lenses stretches beyond its physical edifice, such that the total lens assembly lies between it's optical center and it's focal plane. However a normal lens with a focal length which is longer than what's thought of as a normal lens dies not necessarily make it a telephoto lens.

Northern Red Tail Hawk
Northern Red Tail Hawk Photographed with a 500mm Focal Length

A telephoto lens always incorporates a special group of lenses referred to as a telephoto lens group (see comments below); however, non-telephoto lenses with long focal lengths are most often informally labeled as telephoto lenses. An angle of view formed using a telephoto is identical to that created by a normal lens of the identical focal length. A telephoto can either be a prime or a zoom and work with SLR film cameras, DSLR cameras in addition to MLIC cameras

Telephoto Lens Variations Discussed

Telephoto lenses deliver a more narrow view compared to a normal lens. They have long focal lengths plus they have narrow viewing angles.

They're available in many different focal lengths, while the longest (plus most expensive) ones challenge the capability of telescopes for magnifying images. Image magnification isn't the sole use for telephoto lenses. Their shallow field depth makes them desirable for diminishing unwelcome foreground and background entities by  making them simply out of focus. In addition, their shortening uniqueness can make portraits appear much more natural and pleasing, and can visually compact far off objects so they appear closer.

For example. he setting sun, can appear so much nearer and bigger when photographed using a telephoto lens. Magnifying images, is the most insignificant characteristic of extremely long telephoto lenses. A photographer shooting sports can acquire a photo of a pass receiver or high jumper appears as though they were hardly any distance from of the athlete. Such images are possible because of the magnifying abilities of super telephotos. The photographer might have been eighty yards away, however the close-up photo became feasible because of a high-power telephoto lens.

Sigma 50-500mm Lens
Sigma 50-500mm 10x HSM OS zoom lens. Just think of it as a 500mm telephoto lens having a reverse zoom that works with digital cameras

Precise focusing is required when using a telephoto lenses as they encompass an inherent shallow field depth. Their viewing angle is quite narrow while the lens can weigh a lot, a tripod is practically necessary to guarantee accurate, continuous, placement of the subject . These longer focal lengths can also preclude holding the camera by hand less of a choice since shutter speeds need to be fast to steer clear of subject movement or camera blur . When shooting using a telephoto with a lengthy focal length, it's essential to use a sturdy tripod to guarantee sharp photos.  Telephoto lens lengths can be divided into three categories.

Moderate Telephoto

Telephoto lenses moderate in length (85mm to 130mm lenses for 35mm cameras) (55mm to 85mm for APS-C image sensor cameras) may be held by hand with fast enough shutter speeds, and they are perfect for shooting portraits, especially head and shoulder photos or headshots. As a matter of fact, a 105mm is most often thought of as the classic lens for portraits.

A 200mm lens can even be easily held by hand when shutter speeds become faster than 1/200 second. (Take a look at Shutter speeds for particulars out using your camera while avoiding the use of a tripod.)

When you can get closer physically, these lenses are terrific for bringing landscape features nearer, and for shooting parades, including crowd scenes, school events for your children and even stage shows.

Medium Telephoto

135mm to 300mm lenses on 35mm SLR film cameras (or 90mm to 200mm on APS-C cameras) are thought of as medium telephoto lenses, making them different from moderate or super telephoto lenses.

A fast 135mm lens (90mm on a APS-C) is a no-nonsense lens for action shots and candid wedding photography when your subject is not too close nor too far off, since it's not too heavy, it can be hand held easily and is just for singling your subject out. It is also an excellent portrait lens.

The 180mm to 200mm lens is a perfect range for sports when the action happening right under your nose. If you are way high in the bleachers, you'll need a lens with more-power. This lens magnitude are also good photojournalism lenses. lens speed is critical for this focal length lens. A slow 180mm lens will be of little use, while an f/2.8 fast 200mm lens apt to be your most-often-used candid lens as it lets you to capture the action as you bring it in close using a fast shutter speed.

A 300mm lens will everything a 200mm lens does, except it brings your subjects in closer. The big issue with lenses of this magnitude is that the fastest and the best ones are acutely expensive. However, I question the merits of acquiring a 300mm lens /5.6 even /4 maximum aperture to shoot action photography, as the necessary shutter speeds are most often so slow and that a majority of the time you will be unable to acquire fast-moving subjects without image blur, even when setting a high ISO or using fast film. However, a 300mm lens with an /2.8 fast maximum aperture is extremely costly. Naturally, if you don't require fast shutter speeds then your 300mm lens doesn't have to be fast. although using a tripod still is fundamental.

Super Telephoto

High powered telephoto lenses from 400mm to 800mm and up are the most expensive, for the slowest lenses even, however they provider the ultimate in telephoto photography. Deep pockets are necessary for every lens in this category, in particular the faster varieties, as a single lens might cost as much as $9,000 or more which is more money than a typical consumer will spend on photography over their entire lifetime.

A premium 400mm /2.8 lens may be the ultimate dream lens of numerous wildlife and sports photographers, something they might save for over many years to acquire. A 600mm /4 lens may be even more fantastic, although the 16x magnification of an 800mm /5.6 lens has the ability to be used in astrophotography resulting in sharp, colorful images.

The principal users of these exotic lenses are professional photographers are. A large amount of the images seen in sports magazines and newspapers are photographed using these lenses

Telephoto Lens Construction

If an optical lens were made from a single 200mm focal length, then while the lens is subsequently focused upon an object using infinity, the lens would be 200mm distance from it's focal plane on where the image sensor or film is located. A lens center is called the optical lens center. Although building the lens from several elements to diminish aberrations, the optical center from within the construction still exists.

500mm Lens
A 500mm lens that's not a telephoto lens

As such a lenses focal length increases, the lens physical length becomes problematically long. However these types lenses aren't telephoto, no matter how tremendous the focal length. They are just simply lenses with long focal lengths. A telephoto lens operates by building the outermost (the one that gathers light) element with a much lesser focal length over the long-focus equivalent lens and then fitting in a second element set close to the sensor or film plane that lengthens the light cone so that it seems to have originated from a much longer focal length lens.

The diagram to below depicts the fundamental construction of a typical telephoto lens. It is made up using front lens elements which, contain a positive focus as a group. This groups focal length is not as long as the lens effective focal length. The rays converging from this lens group are captured by the rear group of lenses, on occasion described as a "telephoto group," which contains a negative focus. The most simple telephoto lens designs could be made up from a single element within each group, although in actual use, more than only one element is included for each group to remedy for a variety of aberrations. These two groups combined results in a lens assembly which is physically not as long as the long focus lens delivering the identical size image.

Lens Diagram

This same property can be achieved using mirrors which are combined using lenses in catadioptric type designs. The mirrors used in such designs bend the light path while a curved secondary stretches the light cone, allowing the lens to be not nearly as long as it's focal length even with the folded layout. However, lenses that incorporate mirrors are not automatically telephotos.

Compared with the opposite results employed in retrofocus lenses, occasionally labeled inverted telephotos, by having more clearance between the rear element and the film or image sensor plane of what their focal extent would allow using a conventional optical wide-angle lens layout. Zoom lenses which are telephoto at one end of their zoom range while being retrofocus on the opposite end are now common place.

Mirror Telephoto Lens Diagram

The telephoto lens that weighs the most was made by Zeiss featuring a 1700mm focal length of with a maximum f/4 aperture, with an entrance pupil of 16.7 inches. It was designed to be used on a Hasselblad 203 FE medium format camera and weighs 564 pounds.

Zeiss Super Tele 4/1700

Telephoto Effects

Telephoto lenses and other extended-focal-length camera lenses are best used for allowing distant objects to appear magnified. This result is similar to relocating closer to your subject, however is not exactly the same, because perspective is an exclusive function of a viewing location. Two images acquired from an identical spot, one using a wide angle while the other uses a telephoto, will show the exact same perspective, in that both far and near objects appear to be the identical relative size one another. In comparing magnification with a long lens with magnification by moving in closer, on the other hand, the telephoto image seems to compress the space between objects because of the perspective of the farther away location. As a consequence, long lenses give the photographer a substitute to the sort of perspective distortion revealed by lenses with shorter focal lengths when a photographer is closer to a particular subject, different sections of a subject within a photo can appear in disproportion to one another.

Long lenses also allow for easier blurring of backgrounds more, even as the field depth is identical; photographers will often use this technique to defocus an image background to "disconnect" it from their subject.

If you are sincere about architecture, landscapes, long telephoto images, poor light or night photography, a sturdy tripod with even a better tripod head might just be the best camera accessory you ever acquire. When you want the ultimate in image quality, having a first-rate tripod should not be underestimated .

Different Focal Lengths

Effect of different focal lengths on photographs taken from the same place: 50mm 100mm 200mm, 300mm, 400mm and 500mm The photos below were shot using a 35mm camera, using the Sigma 50-500mm lens of the given focal lengths with the tripod set in the same exact spot.  Click on an image for a larger photo,
 
Oak Grove Regional Park-Sigma 50-500 Focal length 50mm
Sigma 50-500 at 50mm
Oak Grove Regional Park-Sigma 50-500 Focal length 100mm
Sigma 50-500 at 100mm
Oak Grove Regional Park-Sigma 50-500 Focal length 200mm
Sigma 50-500 at 200mm
Oak Grove Regional Park-Sigma 50-500 Focal length 300mm
Sigma 50-500 at 300mm
Oak Grove Regional Park-Sigma 50-500 Focal length 400mm
Sigma 50-500 at 400mm
Oak Grove Regional Park-Sigma 50-500 Focal length 500mm
Sigma 50-500 at 500mm

Constant object size

A photographer often moves about to preserve the identical image dimensions on the sensor for a particular subject. Look at the comparison images shown below, while although the object in foreground stays identical in size, the backgrounds change size; consequently, perspective is dependent relationship upon the distance from the photographer and his subject. Longer focus lenses condense this depth perception, while the shorter focus exaggerates depth perception.

This technique is also used with dolly zooms. This perspective, often labeled as a normal lens, being a 50mm focal length on a 35mm SLR film format, is typically thought of as the "correct" perspective, although a longer length lens is most often favored for a more pleasurable portrait perspective

28mm
28mm
50mm
50mm
135mm
135mm

Teleconverter

A teleconverter is defined as a second lens that is installed between the primary lens and the camera. Its main function is to multiply the crucial portion of an image captured by the primary lens itself.

Teleconverters function much better mounted on a telephoto lens (over 200mm) than on a shorter focal length lens and predictably work better on a prime lens than on a zoom lens.

The attraction of a teleconverter is to select a 300mm f/4 lens which costs around $1200) and by only spending an additional $200 you have a 600mm f/8.lens. Now a 600mm f/4 lens costs more than $7,600 putting it out the grasp of everyone but the most dedicated wildlife photographers

Teleconverters work pretty much the same as a telephoto lens group of a dedicated telephoto lens. They consist of a array of lenses acting together as a single deviated lens. The teleconverter is located in such a way that the image created using the objective is situated behind the teleconverter at a distance less than its focal length. The resulting image is really a virtual entity of the teleconverter that is subsequently focused further away which result are enlarged. As an example by placing a solitary negative lens so that the resulting image created by the objective being situated half way from the lens and the len's focal point it creates the image from its focal point by enlarging it twice As a result functioning as a 2 teleconverter.

updated article Sep 24, 2011

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