Aperture, ISO, Exposure, What does this mean?

How to learn basic concepts about digital photographySure to buy a camera with minimal controls we’ve all asked these questions.

It is logical that at first many concepts frighten us, but quiet, go talk to them slowly and in detail.


The first thing we will discuss is exposure. Basically the show is the amount of light that reaches our sensor. The lighter, the more it will clear the picture and vice versa. For exposure cameras have an element called Exposure Meter. In many manuals and books to refer to the exhibition stands EV (Exposure Value) are used. If we measure the light and the EV value is 0, it means the camera captures the image as it sees it. If instead EV is greater than zero appear clearer picture, and EV is higher against the brighter. This phenomenon is called overexposure. Conversely negative values ​​generate EV darker or underexposed photos. This is a quick definition to understand these concepts. As said, ideally exposure EV = 0, but this depends on the type of photos you want. A photo with a “wrong” exposure can produce images with a high artistic impact.

The next thing to try is how to control exposure, the amount of light reaching my sensor. To do this we have three tools: the aperture, the exposure time and ISO.


Aperture is a basic parameter of the objectives and can make the price of a lens is very high. The aperture is a hole through which the camera can increase or decrease, which allows me to let more or less light. In photography nothing is free and the amount of light that we let the sensor, a new concept called depth of field appears.

A high depth of field indicates that there will be many parties focused on it. In a shallow depth of field, there will be less focused parts. And this is it good or bad? The answer is it depends. For example, in a landscape interests me a great depth of field, to see as much detail as possible. Instead I’m interested in a portrait a depth of field small enough that the person focuses but blur the background to highlight the model.

The depth of field is controlled easily, with more apertures, less depth of field and vice versa.

Each lens has a maximum aperture and minimal. Depending on the price of the target we can have a wider aperture. For the opening of our goal we can read it in your body. Corresponds to an F and a number. For example F4.5 . Funny thing is that against smaller the number, the more open is and not vice versa.

Typical values ​​of openings are:

2.0 2.8 3.5 4.0 5.6 8.0 16 22

Are examples only and there are objectives that are able to close and open to different sizes.

In the body of the lens may appear two maximum apertures. This means that the largest aperture (smallest number) is only available within zoom size, and smaller aperture (higher number) is the maximum aperture at full zoom. As the length of the zoom is greater, the objectives tend to have smaller aperture. There are also targets its maximum aperture is constant at the expense of a higher price.

Exposure time:

This concept is simpler than the previous one. Basically tell the camera how long you should be capturing the image. The more light, the less time you have to be doing the show. The time can be from 1/1000 seconds to minutes. The more time doing this exposure will capture more light, it is easy to understand. So, what should I know?

The exposure time also has its counterparts. If you use a very low time, the picture will freeze but there is a risk that appear underexposed. If time is high, they can appear correctly exposed but move. Here the answer is simple, if the exposure time is greater than about 1/10 second, it is best to use a tripod. Using a tripod is typical indoor or night photography. Using high exposure times may be of interest for example for photographing a seascape, in which an exposure of several seconds is allowed, leaving rocks and well-defined static items and water with an ethereal effect. Here everything depends on our creativity.


ISO is the light sensitivity of the sensor. Against a higher ISO value, the sensor captures more light. Typical values ​​are ISO 100,200,400 to 12,800. High sensitivity is a serious problem. “Noise” appears in the images. Noise is a kind of “texture” (different analogue grain in my opinion) makes the picture loses quality. Avoid the use of high ISOs, but sometimes is a must, especially in low light conditions. Note that the camera manufacturers work very hard to solve this problem, but be aware that depending on which more modest houses, the noise level will be considerable.

In summary, exposure is the amount of light reaching the sensor and thus to be represented in the final photograph. Controlling exposure has aperture, shutter speed and ISO. Each parameter provides an effect that we must consider depending on the type of photography you want.

Post in the following we discuss other basics of photography.


About David Cucalón

About me: I began to make shots in 2008, with Olympus E-510. I like a several kinds of photos, but my favourites are motorsport, first plane, macro and urban shots. I think that digital age make more easy and accessible photography for a lot of people. I’m expect you enjoy with my gallery and feel free to make constructive critics. Welcome to my world. Sobre mí: Empecé a tomar fotografías en el año 2008, con una Olympus E-510. Me gustan diferentes tipos de fotos, pero mis favoritas son competiciones automovilísticas, primeros planos, macros y ciudades. Pienso que la era digital ha hecho más fácil y accesible la fotografía a muchas personas. Espero que disfrutes con mi galería, y siéntete libre para hacer críticas constructivas. Bienvenido a mi mundo
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