Did you do your homework? In my last post I said that you need to read "Understanding Exposure" by Brian Peterson. So if you haven't done so already, hop on over and get that book. It is hands down the only photography book you will ever need.
So what is "exposure" anyway. An exposure is basically the amount of light that your camera sensor will record when your camera shutter is open. In Brian's book he goes into detail and demystifies exposure for you. Really, anyone who wants to take great photos with their DSLR should have this book. But I will do my best to get you up to speed in case you didn't do your homework. ; ) I made this little info graphic to help...
Don't freak out! Stay with me! This is so important and I promise you that it will make sense in a minute...
There are three factors that affect how the light travels in through your lens and onto your camera's sensor.
1. Aperture - this is how big the hole is when the shutter is open. If you have a small aperture number (f/1.4), you have a large hole and more light coming in. That is called a wide aperture. Consequently the more your background will be blurred, this is known as a small Depth of Field, or DOF. If you have a large aperture number (f/22), you have a smaller hole, less light and a greater DOF (your background will be in focus), also called a narrow aperture. We will revisit depth of field later. For right now I want you to think about the amount of light. Small aperture number = More Light
2. Shutter Speed - this is how long that hole stays open. If you have a fast shutter speed (1/4000sec), less light will come in because the shutter is not open long. A fast shutter speed will freeze action (think kid running and scoring a soccer goal.) A slow shutter speed (1/2 sec.) will keep that shutter open longer and allow more light in, but any movement will be blurred.
3. ISO - this is how sensitive to light your sensor is. The higher the ISO (25,600) the more sensitive to light your sensor will be. However, you will lose detail and your image may have grain, or what we photographers call, noise. The lower the ISO (100) the less sensitive to light, but you will retain more detail.
So before you even touch your camera, I want you to think about that for a while. Think about what happens when you need to freeze your child in motion at a soccer game. You need a fast SS (shutter speed). I would probably recommend a SS of at least 1/500 for a soccer game, but I will usually go even faster. If you increase your shutter speed, you are letting in less light. So you may need a wider aperture (which is a smaller aperture number). You also don't want that aperture wide open, because it is difficult to focus on a fast moving subject with a tiny depth of field. So you may also need a higher ISO depending on how bright the sun is and if it is cloudy. So in this case you increase your SS, make your aperture wider (smaller number), and increase your ISO.
And now take it a step further, imagine you are photographing your child playing in a dark gymnasium. You have even less light now and may need to adjust aperture and ISO even more to in order to freeze the motion.
f/5.6 1/1000sec. ISO 250 (bright sunny day)
f/3.2 1/1000sec. ISO 4000 (dark theater)
Do you see how the shutter speed is the same for these images at 1/1000 sec.? I had to change the aperture and the ISO in order to get a good exposure based on the available light.
Of all three elements, I feel that aperture is the hardest one to understand. Because a small number = a wider aperture, more light, smaller depth of field. But once you get used to it, it becomes second nature. We will revisit aperture later.
Now I know what you are thinking. Why can't I just let my camera choose these settings for me? That's what auto mode is for, right? Let's explore auto mode for a minute. Shall we? I will even explore the other modes for you too.
I dusted off my Canon Rebel T3 and took this photograph on full auto mode. Your camera is dumb. Let me repeat that, Your. Camera. IS. Dumb. In auto mode it chooses the three elements for you. It even chooses the focus point for you. It was torture for me to even take this photo in auto mode... It literally made me a bit batty! It's no wonder that people are frustrated with their DSLR cameras. Auto mode shouldn't even be an option. Really, it shouldn't! But I gave it another chance and tried auto again.
Yuk, yuk, yuk. This time I stepped back hoping it would focus better and it popped up the flash. Not at all what I wanted. The reason it popped up the flash was that it chose 1/60sec. as the shutter speed. Without the flash, it would have been a blurry mess. Why camera? Why would you do that? At f/4.5 she is not isolated from the background. The focus is a bit better, but still falling on her armpit and ear. Her armpit for crying out loud!!! The flash washed out the shadows and made the light flat, boring, and harsh. We will talk more about flash later, but we are not quite ready for that yet. Also, it's best to never use that pop up flash. It's just not flattering light at all. Terrible, really!
For the image above, I put the camera on Program Mode. If you shoot Canon it is the "P" on your mode dial. I think it's the same for Nikon. In this mode, your camera chooses all three elements of exposure for you, but you can choose the focus point. Program mode will demonstrate just how dumb your camera really is. This image is underexposed, meaning too dark. You could use something called "exposure compensation" in these modes for this. But light changes and you still wouldn't be able to quickly adjust for it in one of these semi auto modes. You camera is too dumb to do that correctly on it's own.
And now we have Shutter Priority mode (TV on Canon, S on Nikon). You can choose the shutter speed and the camera will do the rest. The thought behind it is you use this mode in situations when shutter speed is the most important given the situation. Sounds great, but then it's changing your aperture and ISO for you, you have no control over those elements. You can see the image is still underexposed. Not what you want.
This image is in Aperture Priority mode (AV on Canon, A on Nikon). You choose the aperture the camera chooses the shutter speed and ISO. While I was able to isolate her from the background more, I still had little control over the exposure and this mode would not have worked well for me had she been moving quickly. When photographing littles... they move quickly without warning. This image is still slightly underexposed.
Eureka...Manual Mode! I was able to isolate her from the background, keep my shutter speed fast enough to freeze her movement on the lowest ISO possible. Her skin is properly exposed. For this image I set my ISO at 250, knowing that I had a decently bright scene. Then I set my aperture at f/1.6 to isolate her from the background. I then metered her skin. (I will talk more about metering next week. Metering is precisely the reason you need manual mode.) While metering her skin, I set my shutter speed at 1/250. That is my personal minimum when photographing children. Had she been moving around more, I would have brought my ISO up and set the SS faster. This image is properly exposed. Keep in mind, that formula worked well in this situation, with this light. There is no one magic formula. You must learn how to adjust for the situation and the light. And you will... practice will get you there. Trust me, once you learn how to control your camera, auto mode will drive you absolutely batty.
As a side note, manual mode does not mean that you are manually focusing your camera. Your camera is still on auto focus (AF). Manual mode simply means that you are choosing the three elements of the exposure for the camera in order to obtain a correct or your "creatively correct" exposure for the given situation. I will teach you how to choose your focus point, but your camera will still focus for you.
I know it's a lot. You probably feel a bit overwhelmed right now. But I hope that I've showed you how shooting in manual mode is so important. It becomes even more important when you find yourself in different lighting situations, like the beach or a dark gym. I promise that once it clicks for you, you will be so happy that you flipped your camera mode to manual. So, for your homework this week, I don't want you start clicking away with your camera just yet. I do want you to review your camera manual and find the controls for ISO, Aperture and SS. Also, think about the three elements of the exposure triangle and how they work together to affect the amount of light coming into your camera. Next week, we will talk about metering and how to get a proper exposure using those three elements of the exposure triangle.
In the mean time, if you have any questions please feel free to email me. I'm here and happy to help!
Next week, we meter! : )