Simply put, exposure is the amount of light portrayed in a photograph. (Which is why I chose the above image - it has a lot of light!) One of the number one goals in any type of photography is getting the perfect, or correct, exposure (or at least an exposure within an acceptable range that can be tweaked in Light Room or Photoshop). "Over-exposed" images are too bright while "under-exposed" images are too dark. Exposure can also be a matter of taste; in the above image, I wanted the light coming in the window to be bright. Looking at this in real life, I could see the cars going by behind her and a house across the street, but I knew that if I over-exposed this image a bit, I wouldn't see those things - I would just see a beautiful bride and beautiful, natural light on one of the best days of her life. Other photographers may not have over-exposed this image the way that I did. Beyond being a matter of taste though, you do have images that are too far one way or the other:
We've all seen (and taken) images of this nature. Both images above are too far gone to save...well, at least beyond my skill level. With under-exposed images, many details are "burned out" and cannot be seen. In the above image, you can barely make out the right eye. In over-exposed images, many details get "blown out". In the over-exposed image above, you can't even make out details on her shirt. And, I did not Photoshop these images to make them worse - both were taken while I was testing a little point and shoot camera that we bought. Well...this isn't the point and shoot camera for us, but that's a whole other post.
So what affects exposure? Well, obviously there are external factors that affect it, like sunlight and flash. But today, I'm going to focus on the things inside the camera that affect exposure. This is important to know because when you shoot in manual mode, you will adjust your settings based on what will give you a desired exposure - so, it helps to know what you need to adjust and why. There are three settings inside the camera that directly affect exposure: ISO, shutter speed, and aperture.
ISO - In the old film cameras, ISO could be equated to film speed rate. But, if you are using a digital camera or a DSLR, ISO is a rating of the camera's sensitivity to light. ISO 100 would be a lower sensitivity than ISO 1600. ISO settings are a balance. In a dark place, like a gymnasium or a church, it may be tempting to set your camera to ISO 3200, but many times what you will get are dull, grainy pictures. Your goal should always be to shoot in the lowest ISO you can. In lower ISO settings, though less sensitive to light, the camera will yield better saturation and be of better quality. In higher ISO settings, your pictures will have less saturation and will get noisier and grainier the higher you go. But, because the higher setting makes your camera more sensitive to light, you are able to use higher shutter speeds and apertures. So, if you are shooting outdoors, set your camera to ISO 100 or 200. When I'm inside, I try to keep my camera at ISO 200, but if the room is dark, I will go up to ISO 400. If I'm shooting a wedding in a dark church, I will go up to ISO 800. I try really hard not to go beyond that by adjusting my other settings. As I said, it is a balance.
Aperture - Aperture is the size of the lens opening. Think of aperture as a window; the larger the window, the brighter the room. So, a large opening (f/2.8) will let in more light than a small opening (f/18). It is confusing at first that the numbers seem opposite; f/2.8 is a larger opening than f/18, but that is something you get used to over time. Aperture is also a balancing act. Why wouldn't you simply shoot with the largest opening you can all the time? Beyond exposure, aperture also affects your depth of field, and that is why you cannot use the same aperture setting for every scenario. But, depth of field will be covered more in depth in the next "Getting to Know Your Camera" post. :)
Shutter Speed - The camera can only record information when the shutter is open, so shutter speed is how fast the shutter opens and closes again. It is measured in seconds - a shutter speed of 1/160 is one one-hundred-sixtieth of a second. A shutter speed of 1" is one whole second (which, by the way, is a very slow shutter speed!). The slower the shutter speed, the more light that is let into the camera. If aperture is the size of your window, shutter speed is like a mini blind on the window that is being opened and closed. The faster I open and close the mini blind, the less light you will see. But, if I open and close the mini blind more slowly, more light will creep into the room. And, like all of the other settings, this is also a balance (I bet you knew I was going to say that!). Although slower shutter speeds let in more light, the slower speed cannot stop motion like a faster speed can. So, if you are at an old, dark gym taking pictures of a basketball game, you could adjust your camera to a slower shutter speed to let in more light, but your players would be a blur. High and low speed photography will also be covered more in depth later. Just like aperture, shutter speed is a topic that deserves an entire post all to itself.
These are the three settings that affect exposure inside of the camera. When you shoot in manual mode, you will constantly be balancing and adjusting your ISO, aperture, and shutter speed based on the situation at hand. Here's an illustration - Let's say your cousin is getting married, and you're good pals, so you want to take some nice pictures at the ceremony for her. The program states that no flash photography is to be used during the ceremony, and the church is pretty dark. What do you do? Well, I might start by setting my camera to ISO 400, f/2.8 for the aperture, and shutter speed 1/80. I would take a picture and see how it looks. If it is dark, I would set the ISO to 800 and take another picture. If that's better, I might set my shutter speed to 1/100 to make it a little faster and see if I'm still getting an acceptable exposure. After going through my balancing act and finding the settings that make me happy, I would probably leave the settings alone for the duration of the ceremony, assuming that the lighting doesn't change. It may take me 10 test shots to get exactly what I want, but the more practice you have shooting in manual, the faster that process goes. Eventually, it becomes somewhat automatic. :)
Guest blogger is Corrine Corbett of Timeless Blessings, is a stay at home mom and photographer wielding a Sony Alpha 500. As a guest blogger she hopes to teach you all things that will take the frustration out of photography and leave you more and more satisfied with your art. Her current eye candy comes from Morgan Kervin, Denise McCabe and Isabelle LaFrance.
"I have learned so much from other photog bloggers out there.
I'm really looking forward to the opportunity to pay it forward with anything that I learn! :)"