What is exposure? A Beginner’s Guide to Exposure Photography

Exposure is one of the first concepts to learn when entering professional photography. Let’s learn about exposure photography for beginners with Tnhelearning.edu.vn in the article below!

What is exposure?

Exposure is a term in photography that refers to the amount of light the sensor receives during the process of taking an image . This is a decisive factor to the brightness of the image , assessing whether the photo is overexposed or underexposed.

There are three factors that affect the exposure of a photo: Aperture, shutter speed and ISO sensitivity, these three factors are called the exposure triangle.

To take a good photo, from sharpness to depth of field, you need to balance the exposure triangle . To do this you have to go through a real training process.

On most cameras today, the above parameters are automatically adjusted in the camera’s presets, but these settings only work in certain environments .

In low light, overexposed shooting conditions, or in harsh conditions such as shooting in the rain, capturing fast movement and wanting to create a beautiful artistic effect you have to adjust the exposure triangle manually.

In cameras the brightness of a photo is expressed in EV (Exposure value) . EV = 0 means that the image is exposed for 1 second at f1 focal length, each step up and down (stop) increases or decreases EV by half.

Exposure triangle

The three values of aperture, shutter speed and ISO are closely related. When you adjust one value, the other two must also change. Below is a brief overview of these three factors.

1. Shutter speed

Shutter speed is the amount of time it takes for the camera to take a photo. For example, on the Nikon D850, you can shoot with any shutter speed from 1/8000 second to 30 second, as well as a time mode for longer exposures.

Shutter speed is crucial when it comes to exposure because:

– A long shutter speed allows a large amount of light to pass through and conversely a shorter shutter speed allows less light to pass through . As you can imagine, if you take a normal daytime photo with a shutter speed of 30 seconds, you will get a completely white photo, whereas if you take a picture at night with a shutter speed of 1/8000 second. , the image will be completely black.

To make it easier to understand, you can refer to the image below:

– Shutter speed creates motion blur effect for photos . A long shutter speed (such as five seconds) will capture anything that moves during the exposure. If one were to pass by, they could appear as an extraordinary light streak across the image. This is called motion blur.

Using a fast shutter speed makes it better to capture fast motion . For example you can take a picture of a waterfall at 1/1000th of a second and see the water droplets in mid-air without the camera being visible to the naked eye.

You can see the difference in the image displayed when changing the shutter speed as shown in the image below, the scene taken on a windy day:

Your photo may be blurry due to two reasons: Camera shake (camera blur) or subject blur (subject blur) makes the captured image blurry. If the camera is shaky then using a tripod can be limited, but the subject you want to capture in motion, like a landscape shot on a windy day, you ‘ll need to adjust the shutter speed to get the image clear .

You can also adjust the long shutter speed to create beautiful motion effects such as capturing the movement of light or capturing the movement of clouds for a smoother look.

When you zoom far to take a photo , the image will be prone to blur, now you need a short shutter speed to capture the movement of the subject, especially when you use a large telephoto lens.

There are no specific guidelines for shutter speed that you need practice with, but there are a few small suggestions you can refer to:

• Use 1/500 second or faster for sports and wildlife activities.
• Use 1/100 second or faster for telephoto portrait images.
• Use 1/50th of a second or faster for wide-angle portraits or travel shots, where your subject doesn’t move too much.
• If your subject is completely still and you have a tripod, use whatever shutter speed you want.

2. Aperture (Aperture)

Aperture

Aperture is the opening of the lens to let light through . Just like the pupil in our eye can contract or open to receive light.

This part on the lens is called ” aperture blade ” these blades can be enlarged or narrowed , the mechanism of action is like the pupil in our eyes, when it is dark, the pupil dilates to receive more light. brighter, also when it is dark you open the aperture of the lens wider so that the sensor receives more light.

Aperture is indicated by the symbol f/parameter. Example: You can have an aperture of f/2 or f/8 or f/16,…

The smaller the parameter, the larger the aperture . You can refer as in the picture:

Aperture and exposure

To properly expose a photo, it is important to pay attention to the aperture setting.

The larger the aperture, the brighter the photo will be . Large apertures like f/1.4 and f/2 allow you to see in the dark. On the other hand, an aperture as small as f/16 (with the aperture blades close to closed) will result in a much darker image. If you try to take a picture of the night sky at f/16, your photo will be black.

By changing the aperture and shutter speed settings, you can precisely adjust the amount of light to get the right exposure. This is why aperture is so important when it comes to exposure.

Aperture and depth of field

Aperture is also an important factor affecting depth of field.

Depth of field is how sharp the scene is from front to back. For example, landscape photos have sharpness on each scene from the foreground to the horizon, while portraits have outstanding sharpness in close subjects, even only in the eyes, and the background behind is blurred. than.

Aperture helps change the depth of field, which makes a big difference if you want to take the best photos possible. Changing the depth of field in an image changes the photo completely.

In particular, a small aperture (like f/11 or f/16) gives you a large depth of field that makes every part of the image from front to back appear sharp. A large aperture (like f/1.4 or f/2.8) achieves a much thinner depth of field, with a shallow focus effect that helps you bring out close-up subjects while others blur.

In fact, the effects are quite obvious. As your aperture gets smaller and smaller, your exposure will get darker and darker and your depth of field will increase. (Also remember that you can return the image to normal by using a longer shutter speed.)

3. ISO – Sensitivity

ISO brightens your image, but it is not part of the exposure because ISO does not affect the amount of light reaching the camera sensor (by definition of exposure). Instead, ISO brightens the image after the sensor has been exposed to light.

The ISO speed will be very useful when there is no way to lighten the image , for example you have opened the aperture all the way and the shutter speed is too long to increase any more, now you can lighten the image more. By increasing the ISO, however, the higher the ISO, the more noise the image will have .

For example in the picture below, the photo on the right looks more grainy, in the dark corners the color of the image is also changed because the photo was taken at ISO 25,600, which is an extremely high ISO (more than what most people think). The photographer will put for normal conditions).

The key levels on the ISO scale are 100, 200, 400, 800, 1600, 3200, and 6400. Some cameras go beyond this range, in either direction lower or higher, such as ISO 25,600 images. above. Alternatively, you can set intermediate ISO values, like ISO 640 or ISO 1250.

The lowest ISO on your camera is called the base ISO . Normally, the base ISO will be 100, but some cameras have ISO 64, ISO 200. If you set the base ISO and expose the image properly, the image quality will be very good and the noise will be minimal. .

Like the photo above at ISO 100, the image is too dark, at ISO 600, though when zooming in, the image will be noisy but still acceptable. However, it’s still best to use your base ISO whenever possible, instead of going higher you should shoot with a brighter exposure (shutter speed and aperture).

Adjust the ISO depending on the actual situation, because sometimes you can’t increase the shutter speed longer, the light is too low, and you may miss a good photo if you just use the base ISO.

How to set up to adjust exposure in each case

1. Learn about camera exposure modes

M mode (Manual): Full manual mode, you will have to control all three factors: aperture, shutter speed and light sensitivity.

P mode (Programed auto): After the camera has calculated and selected the shooting parameters, but allows you to change these parameters as you like.

S or Tv (Shutter priority) mode: Shutter priority mode, you choose the shutter speed and the camera will calculate the aperture according to ISO. You can change the ISO level to control aperture indirectly. You should use this mode when you need to avoid camera shake caused by the handgrip, now you can set the shutter speed fast enough to catch the movements without blurring.

A (Aperture priority) mode: Aperture priority mode, you choose the aperture and the camera will set the shutter speed according to ISO, when you change the ISO levels, the shutter speed also changes. This mode is often used when shooting landscapes, you can change the aperture to control the depth of field as you like.

2. Hints for good exposure in some situations

Daytime landscape photography

– Use a tripod so that the shot is not shaken.

– Switch to aperture priority mode, where the camera automatically sets the shutter speed and you manually select the aperture.

– Shoot at f/8, but use f/11 or f/16 if you need more depth of field (such as with a foreground foreground or if you use a telephoto lens). Here’s how you can adjust aperture on a full-frame camera. Use your camera’s equivalent aperture by dividing these numbers by the crop factor of the camera you’re using.

– Use base ISO.

– Take the shot while adjusting the aperture if necessary for proper exposure.

– Pay attention not to make the bright areas on the camera too bright, when adjusting the image, the dark areas can be brighter, but the too bright areas will be difficult to darken, sometimes damaging the whole image.

Portrait photography (No flash)

– You can use your hand to shoot or use a tripod, as long as you feel comfortable shooting.

– Use aperture priority mode.

– Choose an aperture that gives you an average depth of field – usually at f/2.8 or f/1.4, depending on how much you want your subject to stand out.

– See your shutter speed. If you start to notice motion blur, your shutter speed is too long and you need to adjust the shutter speed faster.

– Keep your ISO low, but don’t be afraid to raise it if your aperture and shutter speed don’t let in enough light. In lower light environments, you may need to increase the ISO to be able to use a fast enough shutter speed.

– Just like shooting in the landscape, you should pay attention not to let the bright areas on the photo be too bright. Use negative exposure compensation if necessary in post-production.

Sports and wildlife photography

– Use a tripod or use your hand to hold the camera.

– Use aperture priority mode. Some guides will suggest you to use shutter priority mode, which is great if you’re trying to learn about motion blur, but this mode often adjusts your aperture to strange values and should only be use when you are more professional.

– Use a large aperture, such as f/2.8 or f/4.

– Consider your shutter speed carefully. The shutter speed should be fast, such as 1/500 or 1/1000 of a second, to keep up with fast movements.

– If the shutter speed is large and the image is still blurry, you have to raise the ISO level and decrease the shutter speed, although the image may be a little grainy but it is still better than a blurred image.

– Just like the two cases above, do not let the bright areas be too bright.

The above article guides you to adjust exposure for beginners, wish you can take the best photos!