Apa Itu Focal Length? | Mengenal Focal Length Pada Fotografi

What is Focal Length? | Getting to Know Focal Length in Photography

Focal length is the ability of the lens to see and capture an event . Usually the focal length is written in mm, 22mm, 50 mm. The shorter the focal length, the farther the event is from the lens, the wider the event can be seen by the lens. Conversely, the longer the focal length, the closer the event is to the lens, but the narrower the event can be seen by the lens.

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Each image shows a different focal length. The smaller the focal length number, the farther the object is, but the wider the event that can be captured, and vice versa.

With this type of zoom lens, there are several focal lengths that you can use in one lens. For example, on the 18-55mm kit lens, you can use a focal length of 18mm to 55mm. The process of moving the focal length from short to long is called zooming in, while from long to short it is called zooming out. If a lens only has 1 focal length, it is called a prime lens/fixed lens.

Lenses with a short focal length are categorized as wide lenses, while lenses with a long focal length are called telephoto lenses.

The focal length affects the aperture, focus and blur intensity. Let's discuss together, what are the influences?

1. Effect of focal length on aperture

If the focal length changes, the aperture changes too. For example, on the Canon 18-55mm lens, f/3.5-5.6 IS STM, if you use a focal length of 18mm, then the maximum aperture you can use is f/3.5, but if you use a focal length of 55mm, then the maximum aperture you can use to f/5.6. The way this changing aperture works is called variable aperture. However, there are also lenses that have a single aperture whose aperture does not change when the focal length changes, which is called a fixed aperture/constant aperture, for example the Sigma 18-35mm f/1.8 DC HSM Art lens.

2. Effect of focal length on focus

There are 2 types of lenses, varifocal and parfocal. The difference is with varifocal, when you have locked the focus at a focal length of 35mm, and then change it to a focal length of 100mm, then the focus that has been locked becomes out of focus and you have to adjust the focus again. But with parfocal lenses, you don't need to adjust the focus again when you change the focal length of the lens.

3. Effect of focal length on blur intensity

The intensity of the blur in the photo (background and foreground) can be influenced by the focal length. The longer the focal length, the greater the blur produced by the lens, and vice versa.

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