how dslr focuses

How DSLR Camera Focuses?

You must have read the tips for buying  your first DSLR in the last post. Now, I will tell you that how DSLR camera focuses? To understand the functionality of your DSLR, you need to get back to the basics that how a human eye functions.

See, your DSLR camera functions similarly the way your eye functions. Once you understand this simple concept, you can make well focused shots. The human eye has a wider range and broader perspective. In the same manner, you can enhance the dimensions of your DSLR camera with lenses. I believe, all the innovations have drawn inspiration from the mechanism of human body. It is the most sophisticated machine. DSRL focus system is also based on human eye. 

How Focal Points Determine The Focused Area?

When you wake up in the morning, you take some seconds to focus on things. Similarly, your DSLR camera does not focus immediately. It needs time to recognize the thing with in a scene. You have to tell your DSLR camera what is to be focused and what is to be left out.

For that matter, there are several focus/focal points in your camera. Some DSLRs have 9 focus points or 16 or 19 or more. These are small square boxes. These square boxes tell the DSLR that which specific area is required to be focused in the whole scene.

You have to select the focal/focus point and press the release/click button half way down only. Keep your finger half-pressed on the button. Once your targeted subject is sharp in the viewfinder, you hear a beep sound then press the button more tightly. If you choose the right focal point, you will get sharp and focused image. In case, you chose the focal point away from your desired subject, your subject will not be tack sharp. These small square boxes turn red once they read and lock the focus on the subject.

how DSLR camera focuses

There are 11 focal points in this photo. Red focal points determined the focused area.

Make sure, your lens is on auto focus mode. There are four different modes in a DSLR camera, dedicated to auto focus area i.e. (i) AF-C: Auto Focus Continuous (ii) AF-A: Auto Focus Auto (iii) AF-S: Auto Focus Single (iv) MF: Manual Focus. How these modes work? We will talk about it in future posts. For a time being, you can set your camera on AF-A mode.

DSLR Camera Functions Similar To The Human Eye:

DSLR camera has a beautiful feature to stand out the focused subject from its surroundings. To understand this, raise your any finger in front of your eyes. Keep it very close to your eyes. You will see whole image blurred. Now, move your finger little away from the eyes. Your finger will start getting sharp and focused. It means, there should be a smallest distance from the lens of your eyes to see the things clearly, Right?

how DSLR camera focuses

Similarly, the lens of a DSLR camera works. If You have mounted 18-55 mm lens to your camera. The smallest distance between your lens and the required subject should be at least 18mm. If the distance is below 18 mm like 15 mm or 17mm, the subject would not be focused.

Now, get back to the basics again. Once your finger is focused then the background is blurred. Now shift the focus of your eyes from the finger (foreground) to the background.

how dslr camera focuses

Shifting focus from foreground to background.

You will see that your finger has turned blurry and background is tack sharp. Though, finger is on the same distance from your eyes. In the same manner, you need to focus the subject by pressing the release button half way down with the help of focal points. That is how, DSLR camera creates a blurry background to stand out the focused subject. The lenses play an important role in this science. We name it as shallow depth of field or defocused area. There are different lenses to achieve this kind of specific results. What lens you should buy for your specific need? We will talk about it later.


Many broader technical details/jargons have been left out purposely to avoid the confusion for beginners. Feel free to ask for more suggestions through comment box.

Siddharth Malkania

Siddharth Malkania is a journalism graduate from Indian Institute of Mass Communication. Having worked as a photojournalist for two years, he traveled to Tokyo and brushed up his skills of photography there. Currently, He is a professional wedding photographer based in New Delhi, India.

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