What Is Exposure? (A simple trick to get correct exposure)

what is exposure

Image Courtesy Of ​Dave Morrow Photography

Whether you are a beginner, intermediate, or professional photographer (or videographer); you may be asking yourself, what is exposure? Well, learning how to properly expose your images is said to be one of the most important. If you are a beginner and don’t quite understand all of the smaller details in this realm, do not worry. You can learn anything you put your mind to. With enough perfect practice you can be as good (if not better) than those you strive to become.In this article I will explain to you what exposure actually is, what actually means in photography, the importance of it, and what you can do from this point forward to ensure that you have the perfect exposure; every single time. Just a heads up, this article will be a bit lengthy but take notes and absorb it all. There is a lot of valuable information here. So without further ado, let’s dive right In.

What is exposure exactly

In very simple terms exposure is the amount of light that reaches your cameras sensor. Exposure settings determine how bright or dark your photo or images appear as a final result.

Exposure is not a single setting on your camera. It is actually a combination of two separate, yet equally important settings on your camera. Those two settings would be shutter speed and aperture. Both of which are a part of the three pillars of photography. The third pillar of Photography, ISO, does not actually fall in this category. That is because ISO does not affect the amount of light that actually reaches your camera sensor. What ISO actually does is manipulate the light that has already reached it.Before we get any further in this article I will remind you that practice makes perfect. Actually, perfect practice makes perfect. Nothing of what I’m about to teach you will benefit you if you do not go out and apply what you have learned. There are many people who read a lot of information but don’t actually apply what they read. I really encourage you (once you have read this article in full) to go out in immediately apply what you have learned – and continue applying it in the months to come. I assure that you will see positive results. Let’s move on to one of the three pillars a photography aperture.

Aperture

what is exposure

The red box represents the numerical aperture value

Many people in the photography realm look at aperture in the physical sense as the pupil in your eye. Much like your eye, it will either open and get wider or shrink and get smaller. This depends on the amount of light needed to pass through it. A camera lens accomplishes this with a series of what is called aperture blades. if you look through the front of a lens in the aperture isn’t set to fully open you will see the blades themselves. below is an image of what aperture blades look like in a lens.

aperture settings

Notice the blades nearly close the entire lens. Canon EF lens set at F16

Lenses can range in the amount of blades they have depending on the make and model. The number of blades is typically starts around 8 and can go as high as 24. I will dive deeper in a future article on how the number of blades can affect your image.

Aperture blades themselves act much like your pupils do. At night your pupils open as wide as they can in the darkest situations. What your eyes are doing is allowing in as much light as possible to be able to see. The same can be said in brighter situations. On a sunny day your pupils shrink to allow in less light, because excess amount of light is not needed. These exact same principles are applied to aperture in a lens. Aperture on any lens is written as an f/number. For example, you may notice f/3.5-5.6 on most telephoto kit lenses. What that actually means is the aperture range of the lens from the widest to the most narrow angle. The same can be said about f/2 f/4 f/8 and so on. These are called f stops.

Aperture numbers are actually fractions

One thing that many do not fully grasp for years in photography is that the aperture numbers are actually fractions. So let’s consider the f as the number 1. If you replace the F with the number one you will notice that aperture settings would look like this: 1/2 1/4 1/8 etc.

What this is telling you is that a half is bigger than a quarter in 1/4 is bigger than an eighth. That is represented by how large the opening of your aperture is. the larger the aperture (or larger the fraction, numerically), the larger the opening is in your lens. Which as a result allows for more light.

Remember, the lower the number the larger the opening. Fractions can trick people in thinking that the lower the number means that it’s a lower value.  The lower the number allows for more light 

The image below gives you a visual representation of this information.

aperture settings

How does aperture work with exposure

Seeing as exposure is not a setting and aperture is, the f stops are the settings that either allowing more light or allow less. This works directly with exposure because obtaining perfect exposure is balancing brightness.A larger aperture allows in more light then a smaller one. A large aperture such as F 1.8 allows in much more light than F-16. An F1.8 would allow you to essentially absorb as much light at night or a low-light situation, while F-22 is entirely too small to allow in enough light to see anything in a low-light situation.

To put that in better perspective, on a sunny day at noon your camera is set at F-22. Assuming that your shutter speed is set correctly it will allow you to take a decent photo. Now let’s take that exact same location in spot but at night. That same shot would be completely black. It is no different then your eyes adjusting in a dark room. If you turn out the lights after reading a book, you cannot see anything because your pupils are too small. Your pupils get larger to absorb more light within the room. Replace pupils with aperture and it’s the exact same idea.

The same idea can be reversed. Let’s take that same sunny day, same shutter speed, and set the camera to F1.8. The lens aperture is open too wide and is allowing entirely too much light in your final image. The result would essentially be white. Now let’s take your eyes for example. you exit your home, after being indoors for a while, and you step outside on a clear sunny day and what happens? You squint, because it’s too bright and you have allow your eyes to adjust/pupils get smaller. Again, replace pupils with aperture and that’s how it works.

Now changing aperture does effect other aspects of photography and that’s what we’re going to get into next – depth of field.

Aperture settings and depth of field

aperture and depth of field

Notice how the subject is in focus and the background isn’t – that’s depth of field.  Aperture set at f 2.0

Depth of field is an incredible effect in photography, which is determined by your aperture setting.Depth of field is the distance from the lens to your subject. For example, if your subject is 5 feet away from you, the distance from you to your subject ( that 5 ft) would be sharp and in focus – anything beyond that would be out of focus or not sharp.

The aperture settings on your lens determines this depth of field. Take for instance if you were doing landscape photography. You would want everything in focus. But if you were doing wedding portraits or shots of individual petals on a flower, you would want only your subject to be sharp. Smaller apertures such as f11, f16, and f22 will give you a very large depth of field. These settings are great for landscape or real estate photography. While aperture settings of f1.4, f1.8, and f2 offer a much smaller depth of field. This allows your subject to stay sharp and in focus while everything behind them is blurry.

Bokah

This blurred effect is known as a Bokah. This effect is associated with professional photography and gives a very “dreamy” yet focused effect your images. This effect alone is what sets DSLR cameras apart from any other camera on the market. Take the images below to compare what an F 16 in an F 2.8 image looks like. You’ll notice the difference immediately.

what is exposure

Narrow depth of field on left (f2.8) – Wide depth of field on right (f16)

Note: Jot this down. In photography, the larger your aperture the harder it will be to focus. In terms of video, the larger your aperture the harder it will be to focus and to maintain that focus.

Settings for the sharpest image

There is typically an aperture range that produces the sharpest image. This is a test that should be performed on every one of your lenses. Every lens and manufacturer is different but this is a general idea that works with the majority of lenses on the market.

Typically the sharpest images are produced between the ranges of f4, f5.6, and f8. If you stay within those three settings your image will be the sharpest that it can possibly can be. Personally, I focus more on proper depth of field and composition over sharpness. Remember, sharpness can be added in post production as well. Regardless, this information is still valuable if you strive ultimately for sharpness in something such as landscape, automobile, or real estate photography.Now that you understand aperture a bit better, lets move on to another pillar of photography which is shutter speed.

How shutter speed affects exposure

camera settings

The red arrow/box represents shutter speed.  The blue box/arrow is the wheel to adjust it. Canon 80D

To start the section off, this section will not be doing a deep dive into shutter speed. We will have an entire post dedicated to shutter speed in the near future. With that being said, do not worry, I will provide you with enough information so that you understand what it is and ultimately how to use it effectively.

Compared to aperture, shutter speed is actually very simple. In simplest terms it is how fast your camera takes a photo. The math behind it is just a simple as well. 

Let’s take 1/500 for example (as represented in the photo above). This fraction represents how fast your camera is taking the photo. 1 represents a second and the number below represents a fraction of that second. With a shutter speed of 1/500 your camera is taking a photo at one five hundredth of a second. The speeds vary greatly, which is actually a good thing. It gives you more options to expose with. the shutter speed can vary from 30 whole seconds to 1/8000th of a second.

So how does this affect exposure? It’s quite simple when you think about it. The faster the shutter speed the darker your image is going to be. Let me explain. The time it takes for your camera to take a photo determines the amount of light that hits the sensor in that amount of time. Meaning, the faster your camera takes the photo, the less amount of light hits the sensor. You can use shutter speed (along with aperture) to expose your image perfectly.

How to adjust exposure

Seeing as shutter speed is such a crucial part of photography and video – most camera manufacturers have a quick adjustment wheel.  This allows you to chance shutter speed by rolling the wheel to the left or right to raise and lower it.  This makes it extremely simple to adjust.  The picture in the previous section shows you what to look for.

Other effects of shutter speed

what is exposure

Slow shutter speed.  Image courtesy of Shaw Academy Blog

There are two areas you need to know about shutter speed ( other than exposure) that we will cover here now.Motion blur is a common effect of longer shutter speeds. An example would be if your shutter speed is at 1/50 of a second, and while taking the photo you are doing it handheld – if the camera moves in the slightest degree you will end up with a blurry image. The image is not being captured fast enough, and as a result it’s catching the movement of your camera in the image itself. The best way to counteract this would be to shoot on a tripod.

There is a time where you want motion blur but it isn’t motion of the camera it’s motion of a subject. A perfect example of that would be water (image above). You can simulate water movement in an image with motion blur. Clouds and water are two great ways to incorporate subject blur.

Why ISO is not apart of exposure

As stated above, exposure is allowing the correct amount of light to come through the lens and hit the camera sensor. ISO does not allow or restrict light at all. ISO measures light and amplifies it if you tell it to do so. While you do have to monitor ISO to get the correct balance of light on your image – that is only after it has passed through the lens. It is definitely something you need to keep in mind but know that it does not determine your actual exposure.

The exposure bar

what is exposure

The exposure graph on a canon T6

This is something that I did not understand for my first year taking photos with a DSLR camera. Above is an image showing what the exposure bar ( which is what I like to call it) – actually is.While this tool is great and allows you to know that you are exposed correctly roughly 90% of the time – just like any tool, it is not perfect. What you will want to do is expose your image so that the triangle is at the center or the zero mark. Personally I like to underexpose by one notch, and I will increase that exposure in post ( such as Photoshop) later if I need to. What is essentially does is it guarantees that your highlights will not be blown out and you save all that juicy data.Again it is not perfect, so if you don’t like what you see as a result then change accordingly – but personally I expose with it every single time I take a photo.

How to expose for video

how to expose for video

This section is going to piggyback a bit off the exposure bar setting and just as above this is quite simple as well. It’s called the histogram. On a Canon camera all you have to do to turn the histogram on is to hit the Q button while in live mode. Above you will see an image that shows you what the histogram looks like.To know you were exposed correctly in a video you use the histogram bar to show you whether your highlights are blown out or your shadows are crushed. This can be determined by the extremes on the left in the right. The left side of the histogram are shadows the right side are highlights. You never want to see either side of the graph being touched by the floating histogram in the center. This ensures that your highlights won’t be blown out and your shadows won’t be crushed. Also don’t forget, if exposed correctly you will maintain all the data in the highs and lows which allows you to adjust all that in post ( such as Premiere Pro).

So what are the best settings?

To answer that question I’ll give you recommendations. But ultimately it is your own skill and style that will determine what these setting should be for you.

So here are the recommendations. If you are a beginner go ahead and give these a shot to start and then go from there. If you are intermediate to advanced (possibly semi-professional), you can look at these settings and determine if they work for you or not and adjust them accordingly. I will also give general recommendations for each setting.

Aperture

The aperture should be set to a number that is determined by your subject.

Landscape should be set between f8 and f16

Portraits should be set between f1.4 and f4.0

Group photos (such as weddings) f4.0 to f5.6

Subject stands out from everything else f1.4 to f2.8

Shutter Speed

Fast moving objects 1/500 to 1/4000

Regular portraits 1/100

Landscape photography 1/50 to 1/100

Water movement 2 to 4 seconds

Anything below 1/100 should be done on a tripod (in my opinion)

ISO

 Only use if you need to brighten your image because your shutter speed is to too fast to maintain exposure.

A video for you visual learners

I thought I would include a video in this article to help those who are more visual learners and might close the gap in areas that might not make complete sense.

Lets sum it up!

If you are a beginner don’t stress too much about getting some of these settings wrong. We have all been there and all of us are still learning – regardless of how “ professional” we may think of ourselves. 

What you should take away from this article is that yes, exposure is very important. But what is more important is actually going out and executing what you’ve learned from this article today. Play with shutter speeds to see the result of different shutter speeds. Take a shot at 1/8000th of a second and the same shot at 1/50th of a second and compare the two. Turn on Live View mode on your camera and adjust shutter speed from there. You will actively see what it’s doing to your image digitally.

Mess around with your aperture as well. Take a shot at F-16 and then another shot at F 2.8 (assuming your lens allows it), and see how that affects your photo. You can also turn on live preview and see how it’s affecting your image digitally in real time.

Remember ISO only adjust brightness from face value. so if you do not need your image brighter, leave it alone.Everything in this article takes practice. Learn what works and practice what works.  Good practice leads to perfect practice which will lead you to your ultimate goal of perfection. Learning, understanding, and executing will take time so be patient and most importantly, love the journey of learning. You can dive deeper into ISO by reading my previous article here. Be sure to sign up for the newsletter which we release once a week. We keep you up-to-date on all camera related news.As always, thank you for reading, and keep shooting!

Jeff

I have been taking photos and film since I was a child. Now that I'm in my mid 30's, I want to share with the world what I have learned over the years. I attempt to live every day to the fullest and share that with you through my blog. I am an electrician by trade and photo and video lie within the "hobby" aspect of my life at the moment. It's what I'm truly passionate about.
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