Exposure Triangle & Lighting

Welcome to my first blog entry! 

I know, I know. Why did I have to start with something so boring? With my series of on-camera flash and off-camera flash workshops coming up later this month, I thought it would be a great time to go over some important lighting basics. Understanding the following concepts will allow you to quickly dial in your exposure in any situation. I know it may be a little bit dry but it's really important to have this memorized if you want to avoid chimping behind the camera (constantly looking at the back of your camera while making adjustments) and losing the trust of your clients. So, put on your big boy and girl pants and let's go over the concepts I use to light all of my clients!

The first thing I want to go over is the exposure triangle. As you can see below, the triangle is composed of three camera settings: aperture, shutter speed and ISO. 

Aperture is a measure of how open or closed your lens is. A wider aperture (or lower F-Stop) means more light will be let in by the lens. A narrower aperture (or higher F-Stop) allows less light to reach the sensor. Aperture is your storytelling device. If you want to isolate your subject, you can choose to shoot at a lower F-Stop (ie: 1.4, 2.0 or 2.8). These lower f-stops create amazing background blur or bokeh. This is the preferred way to shoot outdoor portraits. You've probably heard someone say that they like shooting "wide open." This simply means shooting with the lowest available aperture on any given lens. 

Shutter speed is a measure of how long the shutter remains open and how long the sensor is then exposed to light. Faster shutter speeds give the sensor less time to collect light and result in a darker exposure. Slower shutter speeds allow more time for the sensor to collect light and result in a brighter exposure. The reason you want to use a higher shutter speed is to stop motion. Sports photographers utilize a higher shutter speed to freeze subjects such as athletes or balls. The reason you want to use a slower shutter speed is to slow things like light trails or water down. It is often utilized in night photography due to the increased amount of light let in. The lower the shutter speed the more difficult it becomes to handhold your camera. I rarely handhold my camera with shutter speeds of 1/100th or less. To ensure a sharp picture, a tripod is often needed. 

ISO allows you to increase the sensitivity of your camera. Increasing ISO allows you to work with less light and is often used for handheld night photography or indoor photos. Unfortunately, increasing your ISO results in increased noise and less detail. Modern cameras typically can deliver useable images with ISO settings of up to 2000. 

Now that you understand what the exposure triangle is comprised of, let's discuss how they impact one another.

The way I like to shoot is by figuring out what my aperture is going to be first and then adjusting everything else from there. Remember, aperture is your storytelling device. If I'm shooting a sunset photo of a couple with a light, I want want to see all of the detail in my frame and I will likely choose an aperture of F8 or F11. If I'm shooting a natural light photo of a bride, I will typically choose an aperture of 1.4, 2.0 or 2.8. You may have noticed that your camera allows you to use apertures between the ones I've mentioned and in the chart above. The reason I use these is that they are your camera's F-Stops. Each F-Stop is double or half the light of the previous one. As an example, going from F 1.4 to F 2.0 is half the amount of light let into your camera's sensor. The opposite is then true when you go from F 2.0 to F 1.4. This will double the amount of light let into your camera's sensor. 

Shutter speed and ISO work in a similar fashion. Increasing your shutter speed from 1/100th to 1/200th is half the amount of light let into your camera's sensor. Reducing your shutter speed from 1/200th back to 1/100th is allowing double the amount of light into your camera's sensor. It's important to point out that your camera's max sync speed with a flash or strobe is up to 1/200th with Canon or 1/250th with Sony and Nikon. In other words, you can't use your lights over your camera's max sync speed. Of course fancy lighting systems these days also allow for high-speed sync which is anything over your camera's max sync speed. Unfortunately, this is done at a reduced amount of power. I rarely use it with a flash and save it for my strobes because they typically have power to spare. This is great when I am trying to shoot someone with a shallow depth of field and an aperture like F 1.4. Being able to dial up my shutter speed to 1/800th will help me to prevent having blown out highlights in my background.  If you increase your ISO from 100 to 200, you are doubling the amount of light. Each time you double your ISO you are doubling the amount of light. The opposite is then true when you cut your ISO in half. Each time you do, you are cutting the amount of light in half. These act exactly like F-Stops with your aperture. 

Now that you understand the exposure triangle and how it works, let's see how your lights factor into the equation. First things, first, you need to determine your exposure by choosing your aperture and then dialing in your ISO. Assuming you are using your camera's max sync speed of  1/200th or 1/250th you will want to use your camera's meter (see chart above) to tell you what your exposure needs to be. When it comes to more natural looking photos, you want your meter to be at 0. If you are looking for something a bit moodier, like me, then you will want to make sure your meter is at -1 or -2. I always do this for my sunset shots. Now it's time to add your light source (flash or strobe). If it has a handy TTL (Through The Lens) function then use it. Some lights allow you to start with with a TTL exposure and then switch it over to manual mode while retaining the power setting determined in TTL. This is the easiest way to do it. If your light doesn't have this function don't worry about it. You can do everything in manual mode. The more you practice, the more easily you'll be able to guess what the power output on your light needs to be. The important thing you need to understand about your light is that it works like your shutter speed. 1/1 power is twice the amount of light as 1/2. 1/4 power is half the amount of light as 1/2. Does that sound familiar? Of course it does! 

In order to put it all together, I need to give you a short quiz. Don't worry, I hated school, the answers will appear afterwards. Let's assume you are shooting a sunset couples session at F8, 1/200th, ISO 100 and your light is at 1/2 power. Your light is on a lighstand and won't move in this scenario. If you wanted to increase your depth of field for a moodier portrait and close down your aperture by one F-Stop to F11 (half the amount of light), what would you need to increase your light power to for the same exposure as what you had at F8? The answer is 1/1 because you cut your light by half when you closed your aperture down to F11. In order to keep the same exposure, you need to double the light output on your light, that's 1/2 to 1/1 in this case. Confused? Let's try one more. Let's assume that you are shooting an individual portrait and you want to islolate your subject from the background. You are shooting at F2.8, 1/200th and ISO 100 with a 1/128th power setting on your light. After taking individual photos of your client, you want to take a picture of your client's family.  I typically take those at F5.6. Referring to the chart above we know that is a two F-Stop increase (F2.8 - F4.0 - F5.6) from F2.8. What does your power output need to increase to? The answer is 1/32nd. We simply took our light from 1/128th past the next F-stop of 1/64th to 1/32nd and ta-da! We have a perfect exposure without having to guess. 

The final thing I am going to cover is light distance from a subject and how it can also play a role. Understanding this requires you to know the basic principles of the inverse square law (refer to our handy chart above for a simple breakdown). The inverse square law can be fairly complex. The easiest way to remember how it works is to assume your light will need to be increased by two F-Stops each time you double the distance away from your subject. This is not exact but it is super close. In other words, if your light is 4 feet away from your subject at 1/32nd power output and you want to move it 8 feet away (double the distance) you will need to increase your light output by two F-Stops to 1/8th. The opposite is then true if you want to cut the distance in half by moving your light closer to your subject. 

I realize this is a lot to take in the first time your hear it. If you're like me and you learn better in person then you are welcome to join me at any of my upcoming on-camera, off-camera and creative lighting workshops. Classes are limited to 10 students so that we can provide you with plenty of hands-on experience. Let us help you to take your photography to the next level in 2019!