One of the things that most take away the dream of every photographer who begins to take his first steps in the world of reflex photography are, neither more nor less, than the objectives. Soon after acquiring your first SLR camera, it is very likely that you will begin to feel the need to acquire whatever objective you cross in front of you in order to make your photographs more impactful, even without really knowing clearly which ones differentiate from one of these. Don't worry, it has all happened to us! If you are taking your first steps in the world of reflex photography, it is very likely that given the anxiety generated by the search for the perfect photo, you start to buy lenses without really having the utility to give them and how to maximize their potential. In today's article I will explain what is the focal length and viewing angle, the differences between the different types of objectives according to their focal length and in which situations it is convenient to use each other so that you can get the most out of them . You can not lose this!
WHAT IS THE FOCAL LENGTH OF A TARGET?Of all the possibilities offered by a certain objective, in today's article I will concentrate on explaining in detail one of the fundamentals: its focal length. If you are not familiar with this concept, here is a simple explanation so you can make the most of this article: The focal length of a lens is the distance that exists, expressed in millimeters, between the sensor (focal plane) and the optical center of the lens. What is the optical center? To avoid getting into many technicalities, the focal length is not measured from the sensor to the front lens of the lens, but is the point where the rays of light intersect within it and are directed towards the sensor. This point is very close to where the diaphragm is. Keep in mind that, depending on the size of the sensor your camera has, the focal length that your lens brings factory printed may vary. Don't worry, I'll explain later how to calculate the actual or effective Focal length. So that you can understand perfectly what the focal length is, it is not enough for you to know that they are each of the symbols that they bring , but that you need to understand what they are used for and what use you can give them when making your Photographs.
EFFECTIVE FOCAL LENGTHThe focal length of a lens, whatever the brand or model of the lens, uses as a reference the sensor size of a Full Frame camera (35mm). Why is this important? Because according to the size of your camera's sensor (Full Frame, APS-C, 4/3, etc.), the effective focal length of the lens will vary. If you have a camera with an APS-C sensor that is smaller than the full or Full Frame format, such as a Canon 700D or a Nikon D3100 , a 50mm lens on those cameras, it will equal 75mm if you use Nikon or 80mm if You use Canon. Why? The focal length of a lens depends on the size of the camera sensor in which it is placed and as the APS-C sensor is smaller than the Full Frame standard, to know the effective focal length, you must multiply the original distance of this by a multiplication factor. This factor is 1.5 for Nikon, 1.6 for Canon, for example. How is this multiplication factor calculated? It is very simple, just simply perform the following operation: Sensor width Full Frame (35 mm) Sensor width of your camera If you don't know what the width of your camera's sensor is, you can check it on the manufacturer's page. It is usually expressed as follows: 23.1 × 15.4mm. The first part (23.1 mm) being the width of the sensor. How does this affect your photographs? Imagine that you acquire a lens with a focal length of 16mm because you intend to go on a trip and portray incredible landscapes, but your camera has an APS-C sensor: the effective distance of it will not be 16mm but 24mm (Factor of 1.5). Result: The objective is not as angular as you might have imagined and the angle of view of it (now I will explain what this means) will allow you to capture a smaller portion of the scene than yes, the effective focal length, was the same as The manufacturer printed on this factory.
FIXED OR VARIABLE FOCAL OBJECTIVES?The objectives of fixed focus are those that, as the name implies, do not allow to vary the focal length for which they were designed, instead, the objectives of variable focus allow to cover a greater path when displacing the position of the lenses and varying the focal distance. But which one should be used? Each type of objective, whether fixed or not, has advantages and disadvantages so choosing the ideal will depend on your tastes and needs as a photographer. Here is a small list so you can evaluate what type of objective you prefer: Fixed focal lens Its advantages:
- Higher optical quality which translates into greater clarity in your photographs.
- Being built with fewer moving parts, they are more resistant and robust.
- Being optimized for their focal length, they produce fewer aberrations.
- Higher brightness that will allow you better shots in low light conditions and less depth of field when working with more open diaphragms (f / 1.4, f / 1.8, f / 2.8).
- Many of them are cheaper than the variable versions.
- They are less versatile since their focal length is fixed. Anyway, I see this as an advantage, since they will force you to move around the whole scene in order to achieve the perfect framing.
- For certain types of photographs, lack of versatility can really be a problem.
- They are very versatile, comfortable and will allow you to adjust the frame without scrolling.
- They are essential for certain types of photographs where you require a greater focal variety, such as nature or sports photography.
- You gather in a single objective a large number of focal ranges so you will avoid constantly exchanging lens in your camera gaining speed and avoiding bumps and dust on the lenses and sensor of your camera.
- They are usually much more expensive than prime lenses, especially those that cover a large focal length such as 18-200 mm.
- By having much more moving parts, they are more fragile in the face of any blow or accident.
- Its weight and size is considerably greater.
- They are less bright, especially in the longer focal points.
VISION ANGLEFocal length is not the only element that you should keep in mind when evaluating an objective, but also, you must pay attention to their viewing angle. In this way you can understand the different possibilities that will allow you to exploit a certain objective when making your photos with it. The viewing angle is something like, the "portion of the scene" that the target can capture from this, but measured in degrees. The more angular the objective, the greater the portion of the scene will allow you to capture in the same photograph, and the more zoom or tele this is, the smaller the portion of the image that you will be able to capture in a photo. For example, a 300mm focal length lens (effective focal length) offers a viewing angle of approximately 8.15 degrees so if you use one, you can fill the entire sensor with a much smaller portion of the scene (sensation of zoom in or out) that if you used, for example, your camera's kit lens at 18mm (76 degrees of view angle), where the same portion of the scene would occupy a much smaller size in the frame. While the objectives are classified and marketed according to their focal length, what is really important is the viewing angle of each of these. Anyway, each focal angle corresponds to a focal length, so if you know both factors well, it's almost like talking about synonyms. If you want to see how this works in practice but you do not have enough objectives to try it yourself, I recommend that you take a look at the lens simulator that Nikon made available to perform all the tests you want, without spending a penny . Objective classification according to your viewing angle :
- Super wide angle: these fisheye lenses can cover a viewing angle 180 degrees or even more.
- Wide Angle: those objectives that cover a viewing angle of between 110 and 60 degrees, which would represent an effective focal length of approximately 10 to 25 mm.
- Standard: are all those objectives that cover a viewing angle of 60 to 25 degrees. From 25 to 65 mm approximately.
- Short tele: are those that cover a viewing angle of 25 to 15 degrees, that is, 65 to 100 mm focal length.
- Telephoto lenses: cover a viewing angle of 15 to 10 degrees, which corresponds to a focal length of 100 to 160 mm.
- Super telephoto lenses: those that cover a viewing angle of 10 to 1 degrees, that is, 160 to 600 mm focal length.