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What is a Good Exposure?

I’ve been involved with photography since I was a little kid. Throughout the years, a lot of people have asked me for help in improving their photos.

I think that there are several concepts that are critical to understanding photography, one of them is how to get the proper exposure. Now, while some concepts do translate from photography to video, there are some very important differences, which is why I’m going to make two videos, one for photography and one for video. This particular tutorial is specific to photography.

I like to keep things simple and so this will be an introduction into what I believe will help you improve your photography skills the fastest. Since I’m sure that most, if not all of the people watching this video are using digital cameras, I’m going to cover only digital. If you are using film, just substitute the word film for sensor.

WHAT IS THE PROPER EXPOSURE

properly-exposed-photograph

The proper exposure simply means that for the scene you are shooting, the proper amount of light is hitting the sensor. It’s really not any more complicated than that. After reading this article I hope you have an appreciation for how amazing our eyes are as they do all of this constantly and better than your camera.

First lets look at a few basic exposure-related concepts.

Overexposure

overexposed-photo

No, this doesn’t mean that you’re not wearing enough clothes. When too much light hits the sensor, a photo will be over-exposed. Over-exposed photos are too bright and a lot of time you lose details in the brightest areas of the photo as they become pure white.

Underexposure

under-exposed-photograph

If not enough light hits the sensor, the photo will be under-exposed. Under-exposed photos are too dark and tend to lose details in the dark areas which become pure black.

Believe it or not, but there are only 2 basic elements in the camera that control how much light is hitting your sensor: Shutter Speed and aperture.

Many people consider ISO to be part of the exposure which it technically is. However, changing ISO doesn’t change the amount of lighting that is hitting your sensor and this is what I want to focus on first. I will cover ISO in more detail later.

SHUTTER SPEED

proper-exposure-shutter-speed

Since it’s a little simpler, lets look at shutter speed first. By default, the shutter on your camera is closed until you click the shutter release button. Shutter speed, is the length of time the shutter stays open when you take your photograph. So for example, a shutter speed of 1/100th of a second means that the shutter opens for a hundredth of a second and then closes. If you used a shutter speed of 1/2 a second, then the shutter would stay open for a half a second.

A shutter speed of 1/50 of a second will let it twice as much light as a 1/100 of a second since the shutter is open twice as long.

Remember that when you see a shutter speed of 100 it actually mean 1/100 or 1 one hundredth of a second. A shutter speed of 1000 is 1/1000 or 1 one thousandth of a second.

Understanding how shutter speed effects exposure is fairly straightforward. Since the sensor is only exposed to light when the shutter is open, the longer the shutter speed, the more light hits the sensor.

If you look at your photo and it is too dark, increasing your shutter speed is one of the ways that will brighten it up.

If you look at your photo and it’s too bright, selecting a shorter shutter speed will allow less light in and give you a darker photo.

APERTURE

proper-exposure-aperture

Aperture (or sometimes you’ll hear people saying f-stop) is the opening in your lens that lets light travel to the sensor. Before we make things more complicated I’m just going to say that a bigger opening will let more light than a smaller opening. I know, earth-shattering. We already know how to make a photo brighter and darker using shutter speed, but now lets see how we can accomplish the same change using aperture.

If your photo is too dark, selecting a larger opening will allow more light in and result in a brighter photo.

If your photo is too bright, selecting a smaller aperture will allow less light in, and result in a darker photo.

F-stops are the numbers used to describe the size of the opening and are what confuses most people about aperture. The reason for the confusion is that as the numbers get larger, the lens opening actually gets smaller. So an f-stop of 2.8 is much larger than an f-stop of 11, which is counter intuitive. You would think that as the number gets bigger, so does the opening.

Without going into too many details, the reason for this is that the number is a part of a ratio for calculating the size of the opening. And although this is NOT how this ratio is calculated, I want you to think of the aperture number as 1 over the number you see.

Meaning, when you see f/2, I want you to think of 1/2 or one half. If you see f/4, think of 1/4 or a quarter.

If you think of it that way, you’ll easily remember that a 1/2 is bigger than 1/4 which is bigger than 1/8 and so on.

What’s most confusing is that people use terms like smaller aperture and larger aperture to describe the size of the opening NOT the number of the f-stop. So when someone says “use a larger aperture” they are telling you to use a larger opening which means a smaller numbered f-stop.

Aperture also has a direct impact on depth of field, but in this video I only discuss its effect on exposure.

ISO

In digital photography and videography, ISO is a setting of the camera sensor’s sensitivity to light. Low ISO like 1 or 200 means the sensor is less sensitive to light and High ISO means the sensor is more sensitive to light. The more sensitive the sensor is to light, the less light you need to achieve a proper exposure.

This is a direct relationship so if you go from 100 ISO to 200 you are making the sensor twice as sensitive, and therefore will need half the amount of light to get the same exposure. If you change from 100 ISO to 400 you are making the sensor 4 times as sensitive to light and will only need a 1/4 of the light to achieve the same exposure.

A basic question I get all the time is “why wouldn’t I just use a high ISO all the time since it means I don’t need as much light?”. The quick answer is that as the sensor becomes more sensitive to light your photos become grainy or noisy.

iso-grainy-noise

A FULL GLASS

One of my favorite way to illustrate proper exposure is to use a glass of water. Imagine that water represents light in this analogy and a full glass of water represents the proper amount of light needed. In order to fill the glass with water we will turn a faucet on and off (just like opening and closing a shutter).

We can control 2 things: How long the faucet is open for (shutter speed) and how big the faucet opening is (aperture).

So to fill a glass, I can either turn the faucet on very low, and leave it on for a longer amount of time.

glass-of-water-small-aperture

Or, I can turn it on full blast and won’t need it to stay on for very long.

glass-of-water-large-aperture

So you can see the inverse relationship between shutter speed and aperture. Basically, the smaller the opening only lets in a small amount of water which means I have to keep it open for longer.The larger the opening lets a lot of water in at once and only a shorter amount of time needed to get the proper amount of light.

ISO in this analogy is the size of the glass. A lower ISO, meaning the sensor is less sensitive will need more light, therefore it would be represented by a larger glass. A higher ISO would need less light, and would be a smaller glass. Remember, changing the glass changes how much water you need, but the relationship between aperture and shutter speeds stays the same.

Finally, a glass that is only half full would be considered underexposed, since I didn’t get enough water to fill it.

glass-of-water-underexposed

An overflowing glass of water would be overexposed since I allowed too much water in.

glass-of-water-overflowing

PRACTICE

There is an exposure meter on the camera that helps you determine what the camera’s computer believes to be a correct exposure for your scene and I think it is a useful tool. The light/exposure meter always give you a great starting point as it uses the camera’s computer to calculate the amount of light that is hitting the exposure.

And although you can use it as a starting point, I really want you to experiment with the concepts I’m going to cover in MANUAL mode which will help you gain an intuitive understanding to these concepts.

There are different shooting modes for DSLRs:

  • P – Program: The camera will choose a shutter speed and aperture, you choose ISO and White Balance
  • Auto – Green Square: The camera will choose shutter speed, aperture, ISO and White Balance
  • A – Aperture Priority: Means you will select an aperture, and the camera will pick a shutter speed for you.
  • S – Shutter Speed Priority: Means you will select a shutter speed and the camera will pick an aperture.
  • M – Manual: Which is what we want to use for practice just means that you have to actively select both shutter speed an aperture.
proper-exposure-manual-shooting-mode

Again, the reason for using MANUAL mode is because I really want you to understand the effect of changing aperture and shutter speed have on exposure. After a little practice, you will be able to take a picture, look at it, make a quick adjustment and then get the results you want.

The beautiful thing about digital photography is that you’re not wasting film. Go out there and take 100, 200 pictures, who cares? If you don’t like any of them, delete them all.

Also, you get immediate feedback for your changes, you don’t have to wait for film to develop.

So when you go out there, make sure that you practice the concepts I discussed. Take the same photo over and over again at different shutter speed and aperture combinations and see what it does to your exposure.

QUICK TIP

Your camera probably has live-view which will let you see the exposure of your current settings right on the screen. You can make changes and get immediate feedback even before you take the photo.

proper-exposure-live-view

CONCLUSION

I hope this article and the video were helpful in explaining the basics of proper exposure in photography. As I mentioned throughout the video, I have only covered exposure which is a small part of achieving a great photograph, but I believe it’s part of a foundation that any photographer should have.

If you have any questions about exposure or photography in general, please post them in the comment section and I will usually get back to you fairly quickly.

If you have any suggestions for how this video could be improved or other topics you want me to cover, please let me know.

I’m very new to posting videos and I would really appreciate it if you LIKED this video or subscribed to my channel.

Thank you for watching.

Comments

  1. I have a car dash DVR camera. Please tell me how to set exposure. The options available are -2, -1, 0, 1, 2.
    Please tell which one to set for night and which one to set for sunny day or cloudy day.

    • what your camera is saying is this: 0 is what it thinks a proper exposure is. -1 and -2 will make it darker. 1 and 2 will make it brighter.

      So it would depend on how you want to alter the image.

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