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If you have ever looked at a camera lens, you will have noticed that they have a series of numbers and letters inscribed on them. These data are all the information of the objective, such as its technical data sheet or business card. With those numbers and letters the objective tells you who it is and gives you more information on how you can get more out of it.

Although each brand uses its own nomenclature, you will usually find four fundamental pieces of information in all objectives: millimeters, aperture, motor and diameter . Let’s see each of them and where to locate them.
Table of Contents
Millimeters
This data is easy to identify. You will see a number followed by “mm”, as in the example:

Los milímetros del objetivo se refieren a la longitud focal que puedes lograr en tus imágenes, es decir, el campo que puedes capturar en la foto o el video. Una manera de descifrar esta información para saber cómo puedes sacarle mejor provecho al objetivo o en qué situaciones te resulta mejor usarlo, es saber que mientras menos milímetros, mayor longitud focal; y viceversa.
Let’s go with two examples to make it clearer:



In other words, a lens with a longer focal length captures a wider scene than a lens with a shorter focal length. With a longer focal length you will be further away than you photograph, with a shorter focal length you will be closer.
And since we are talking about moving away and closer, it is also important that you know that millimeters are different for prime and zoom lenses .


What is the difference? Very easy: on a fixed objective, the millimeters are thus fixed 🙂
In a zoom lens you have a range of millimeters and therefore a range of focal length, indicated by two numbers separated by a dash, as you can see in the example.
Aperture
This data can be found as a proportion in the lens, you will see “1:” followed by other numbers, like this:

¿Qué significan estos números? La cifra que sigue al 1: te indica la apertura máxima que que te permite el diafragma del lente. Como en otros aspectos de la fotografía (y de la vida), menos es más: mientras más pequeño sea el número, mayor será la apertura posible del diafragma. Mira estos ejemplos:

These They are 50mm lenses and differ in the aperture that each one has: 1.2, 1.4 and 1.8 . All three have fixed millimeters and the aperture varies depending on what you program in your camera, reaching the maximum that these figures indicate (1.2, 1.4 and 1.8).
In the case of these fixed lenses, the aperture is also fixed. On some zoom lenses, however, the aperture can be variable and, like millimeters, you will see it represented as a range, like this:

In objectives such as kit lens , or default lenses of some cameras, the aperture may vary depending on the zoom you use. The more you zoom, the smaller the aperture the lens will allow and, therefore, less light will enter.
Tanto los objetivos fijos con mayor apertura como los objetivos zoom con apertura fija son mucho más costosos.
HSM – USM – STM
No, the cat did not go through the keyboard, These acronyms designate the different types of motor that the lens has . Yes, the lenses have motors 😉

First of all, this is what each of them means:
- HSM: Motor hipersónico
- USM: Motor ultrasónico
- STM: Motor de pasos
Now in Spanish. What does all this mean? In short, HSM and USM engines are engines aimed at more professional photography jobs, while STM engines are ideal for hobbyists and video, as they make less noise when you use automatic zoom.
Diameter
This information, which is represented by the lifetime diameter symbol (Ø), is also measured in millimeters:

This measurement is important to buy filters and other accessories since each lens has a different diameter. Even if you have two 50mm lenses, for example, their diameters can vary.
Summary and guide!
Aunque los objetivos puedan incluir más información que estos datos, los cuatro que acabas de leer son los básicos para identificar y diferenciar objetivos. Manejando esta información tendrás más herramientas para sacarle provecho a los objetivos y sabrás mejor en qué ocasiones usarlos.
Remember that:
- El diámetro se refiere a la longitud focal que te permite el lente, mientras menor el número, mayor la longitud focal posible y viceversa.
- La apertura puede hacer toda la diferencia en el precio del lente. Una mayor apertura o una apertura fija en lentes zoom significa un lente más costoso.
- Si estás empezando a tomar fotos, un motor STM es más que suficiente 😉
- Antes de comprar filtros o accesorios ¡asegúrate de que los diámetros coincidan!
And since I don’t want you to forget anything, I leave you this guide so that you always carry it with your camera:
FULL FRAME | CROP SENSOR | IMAGE STABILIZER | SILENT ENGINE | OBJECTIVE PRO | |
---|---|---|---|---|---|
CANYON | EF | EF-S | IS | USM-TSM | L |
NIKON | FX | DX | VR | SWM / AF-S | |
Sony | FAITH | AND | SSM | G / GM | |
SIGMA | DG | DC | YOU | HSM | EX-ART |
TAMRON | GAVE | DI-II | VC | USD | SP |