The possibility of artificially approaching something through a telephoto lens has always seemed fascinating, almost magical. To be able to transform a point in the distance into the precious image of a little bird in a branch, or to be able to capture details and close-ups at distances, never ceases to amaze me.
What is a super telephoto lens?
We consider that a telephoto lens becomes a super telephoto lens when it has a focal length equal to or greater than 200mm.
These are the most commonly used telephoto lenses, the ones with the most variety and the most affordable prices, so it will be about these focal ranges that I’m going to talk to you about today.
The main feature of telephoto lenses
Each focal length is associated with particular characteristics, not only according to what they are capable of bringing us closer or further away from what we want to photograph but also other aspects such as the angle they cover, the distortion, the depth of field or the distance between the different planes of an image.
Angle of vision
It is the portion of the scene that the target is able to capture but measured in degrees. A wide-angle lens, for example, is capable of capturing a large angle of view (around 60°-100° depending on the exact focal length).
On the other hand, a telephoto lens captures much less portion of the scene (smaller viewing angle). As you can see in the graph below, this decreases as we increase the focal length.
Depth of field
The super telephoto lenses are also characterized by having a very reduced depth of field which, translated to the image, means that the background of what we are photographing will always be out of focus.
The longer the focal length, the more this effect is accentuated, which can also be accentuated by playing with the diaphragm opening. Remember that the more you open the diaphragm, the more light will enter the sensor and also the more the depth of field will be reduced (less area focused on the image).
Distance between planes
Another feature of telephoto lenses is how they reduce the distance between planes. That is, the longer the focal length, the more the main figure seems to overlap the background. Look at the following image and you will see how the planes come together as the focal length increases.
What should I keep in mind when choosing one?
There are as many goals as there are needs you may have. But my main advice is that before looking at anything, establish the maximum budget you are willing to spend and once you have it, you start looking at the rest of the features. Because this is as always, the more expensive, generally, the better, there is not much secrecy.