The report photographer or the filmmaker, especially if geographically and naturalistically orientated, must be able to deal with every kind of situation and should know how to respond technically (and creatively) to challenges. Seeing that his equipment often coincides with what can fit into a travelling bag, he will have at his disposal just a selected and limited lenses kit suitable for coping with the various needs that can occur during his work.
However he must show ability in every photographic genre using what he has available in that moment.
Knowing exactly how the same scene will react if captured by a lens with an ultra wide-angle rather than a short telephoto , this provides photographer with a whole range of expressive options from which he can select the best one.
However, those who think that the telephoto lenses are used to film far positioned objects while the wide angle lenses are suitable for filming the nearer ones, they have no idea what it means to take a picture.
Having available in only one instrument a focal length range that can go from 17 to 40 mm, or from 24 to 70 , or from 28 to 300 , is definitely a great comfort. This advantage, however, does not exempt the report photographer to be fully aware that, acting on the ring or on the zoom button , it will change both the prospective and the extension of the Depth of Field (PdC, see the dedicated post). Only this awareness will allow him to choose the best perspective and focal length.
The wide-angle lenses are the ones with the shorter focal length (in mm).
They reduce the distance between the nodal point of lens (the outer lens) and the focal plane (the digital sensor or film), when the focus is set to infinity.
If referring to the standard frame format Leica 35 mm, their upper limit would technically be represented by the length of 43 mm (see the next section on "normal lenses") but are conventionally considered wide-angle lenses the ones that come up to 35 mm.
These lenses have very high field angles (from about 60 ° up to 180 ° of the Fish -eye) and therefore they allow the fixing of very large frame parts, they will be just as greater as the focal length employed will be shorter.
Their main characteristic is to accentuate the perspective effects, enhancing the elements upfront and making the ones which are right behind them smaller and farther.
However, they have several problems of perspective distortion, starting from the disturbing effect of the falling lines.
Under 24 mm we enter the sub-category of the ultra- wide angle lenses.
The lenses called "normal" are the class of lenses that have a focal length range that go from 40 to 70 mm. As most experts know, the real normal lenses are the 50 mm ones because they faithfully reproduce the perspective of the human eye (hence the attribute of "normality") .
It seems to be an approximation because, technically, the same prospect of that of the human vision seen at the same focal length coincides with the length of the diagonal of the frame, and because in the standard format of 35 mm the diagonal of the frame (24x36mm) is 43 mm , the true "normal " should have a focal distance of that length.
Actually, only this objective deserves the title of " normal" !
However, the main characteristic of this class of lenses is to reproduce the elements of the scene while maintaining, between them, the same proportions and the same relative distances that appear to the naked eye.
But, given the great proliferation of sensors of different sizes, it is important to remember that a 50 mm will be "normal" only if used on Full- Frame machine (FF-sensor size corresponding to the traditional 35 mm film). It will become a medium -telephoto when coupled with an APS-sized 16.7 x 30.2 mm. In order to have a normal with this type of sensor lens of 40 mm must be used. The reference is always to consider the diagonal of the sensor.
Above 70 mm we are in the telephoto category. They represent the optics with the greater focal length and the angle of reduced view.
Contrary to the wide-angle, they photograph only part of the scene, to fill the frame with just one or a few elements, thanks to their ability to "approximate" what is far away. Prospectively they represent the inverse of the wide angles, compressing the various prospective plans and reducing the relative distance between them.
From 70 mm to 150 mm the lenses are called medium-telephoto lenses and they are considered the most suitable for portraits. When bigger than 300 mm they are called ultra-telephoto lenses and they are the most used in the photographic hunting... and by paparazzi!