08-April-15: Understanding & Controlling Exposure Settings
I was thinking back to my first few months with a camera in my hand and remembered how complicated it all seemed. For the life of me I could never take the image properly, it was either to dark, to light or the subjects was blurry. I found this so frustrating that it made me wonder whether it was worth continuing as it all seemed too hard.
The problem that I had was I didn’t understand exposure. I knew that shutter speed, aperture and ISO were the important settings, but I didn’t really know what they did or how they affected my images. Most importantly I had no idea that they actually all worked together to give me my final result. It all seems like a bad dream now, and I can’t believe that I ever had an issue, but the fact is when you first pick up a camera it’s all foreign and can be quite confronting and humbling.
Now you would think that having an Engineering background would make all the difference, but the fact of the matter was I never thought about photography in a technical way. But once I decided that if I was ever going to take control of my camera instead of my camera frustrating me I knew that I had to learn how all of these things worked, which is what I did. In this article I am going to discuss ISO, Shutter Speed, and Aperture and how all of them work together. Most importantly I am going to show you where it all finally clicked / came together for me. When this happened my photography immediately jumped many levels and I have never looked back.
So what are ISO, Aperture and Shutter Speed?
They are your light controlling settings. In simple terms each one of these have control over the exposure (the brightness) of your image and you can change any one of them independently to change the brightness of your image.
What are Stops or Light?
I am sure if you’ve had a camera in your hands for some time and have been reading or talking with other photographers you would have heard the term, stops. What this is referring to is a change in the exposure (brightness) of your image.
So if someone says you should increase your exposure by 1 stop this means that you should let double (twice as much) light into your camera. Or is you want to reduce the exposure by 1 stop you should halve the amount of light entering your camera, you may also hear the term “Stop Down” which refers to the same thing, halving the light entering your camera.
You have the ability with your camera to adjust the exposure in 1/3rd increments or 1/3rd of a stop at a time. If this isn’t clear, that’s okay, this will all start to make sense as you read through the article.
Your ISO is how sensitive your camera’s sensor is to light. The lower the ISO the less sensitive the sensor is and the higher the ISO the more sensitive.
Most cameras will work in the range of ISO 100 or 200 up to an ISO of 3200 to 6400. Some camera will go below ISO 100 and some above 6400, but that is the typical range. Also some cameras have settings such as Low 1, 2 & 3 and High 1, 2, & 3 available. These settings are not natural ISO instead they are boosted, the cameras electronics are giving you a result based on what it believes these ISO settings would look like, instead of the actual sensor results, therefore they should be avoided.
One thing you do also want to consider with ISO is the higher the number the greater amount of noise (graininess) will appear in your images. Most cameras today are pretty good up to an ISO of 800, and some are good much past that without introducing a great deal of noise to your images. This is something that you need to consider when adjusting your ISO.
So how does your ISO work?
This is actually pretty simple, if you double your ISO number (i.e. 100 to 200) you are making your final image twice as bright, or increasing your exposure by 1 stop. Conversely if you reduce your ISO by halving it (i.e. 800 to 400), you will darken your exposure by 1 stop. Your camera has the ability to adjust your ISO in 1/3rd of a stop increments as shown in the table below:
Note: If you have a camera where you can adjust the ISO by using a dial, each click of the dial will adjust your ISO by 1/3rd of a stop.
The aperture is the size of the opening in your lens. The larger the opening the more light you let in, and the smaller the opening the less light you let in.
If you have heard the term f-number before it is referring to the aperture, and this is usually written with an “f” in front of a number. The aperture is a little more confusing than ISO and Shutter Speed in terms of changing your exposure by adjusting your aperture. Where ISO and Shutter Speed work by doubling or halving the number, aperture does not, but we won’t let that bother us. The other thing that can be slightly confusing is the larger the f-number the smaller your aperture actually gets and the less light you let enter your camera.
Another thing that you need to consider when adjusting your aperture is the depth of field (the softness / blurriness of the out of focus areas). The smaller the f-number the softer or more blurry the out of focus areas will become. This is a simplified explanation, but for the purpose of this article that’s all we’ll need to discuss.
So how does your aperture work?
So although from a numbering system it’s not as simple, it is actually fairly straight forward to adjust our exposure through adjusting our aperture. Almost all cameras will have an aperture dial on the outside of their cameras, and as with ISO if you turn that dial by 1 click you will adjust your aperture and thus exposure by 1/3rd of a stop. So if you want to adjust light entering your camera by 1 stop you would simply turn that dial by 3 clicks. The table below shows you the standard apertures on many lenses, the aperture number will not change based on the lens used, the only thing that may change is how far you can adjust the aperture. For example some high end lenses will go down to f1.4, where your standard kit lens may not go below f3.5; note also some lenses such as macro lenses may go up to f32 or higher.
So as shown in the table above as you increase the f-number you decrease the size of the aperture and let less light into your camera and conversely as you decrease the f-number you increase the size of your aperture, letting more light into your camera.
Example: If I was shooting at f8 and I wanted to increase my exposure by 1 stop, meaning I want it brighter and I didn’t want to change my ISO or Shutter Speed, I would turn my aperture dial 3 clicks making my aperture larger to let more light in, and my new aperture would be f5.6.
Our shutter speed is basically how long we leave our shutter curtain open, and how long we leave it open determines how much light we let into our camera.
With most cameras we can adjust our shutter speed between 30 seconds and 1/8000th of a second. Many cameras will allow you to keep your shutter open as long as you like with a setting called “Bulb”, in order to do this you will need a shutter release that has a shutter lock or an intervalometer, which is basically a fancy shutter release.
What you need to consider when adjusting your shutter speed is how moving objects will be effected. The longer your shutter is open for the blurrier moving objects will appear in your image and the faster your shutter speed the more those moving objects will appear frozen. Adjusting our shutter speed works similar to ISO. If you want to adjust your shutter speed by 1 stop, it’s a matter of halving or doubling. You also, just as you do with ISO and Aperture, have the ability to adjust your shutter speed in 1/3rd increments. On most cameras you will have a dial to adjust your shutter speed, and if you turn that dial by 1 click you will adjust your exposure by 1/3rd of a stop. If you want to adjust it by a full stop then you would simply click the dial 3 times.
The table below shows you examples of shutter speeds and there effect on the exposure of an image.
So as the table shows you a faster shutter speed reduces light entering your camera giving you a darker image and the slower shutter speed lets more light into your camera giving you a brighter image.
Bringing it all Together
So now that we have a basic understanding of the 3 settings on our camera that can effect exposure, how do we use them all together to get the shots that we want, and most importantly how are they all interconnected?
You will have noticed that in every description given that we have the ability to adjust the exposure of our images by adjusting any one of the three settings. We can now use that information to our advantage to take complete control over the exposure of our images. It all came together for me when I tried a little experiment, and I encourage you to try the same thing.
What I did is thought well if I can have complete control over the exposure by adjusting those 3 items I should be able to achieve the exact same exposure in an image with many different settings. So I tried it, and it worked….it’s basic maths, and you can all do it. In the table below I show you what I mean.
Let’s take an image that we have shot with the following settings: ISO 400, Aperture f8, and Shutter Speed 1/500th of a second, and lets come up with 3 different settings to achieve the exact same exposure.
What you will notice above is, if you want to maintain the same exposure as the original image you need to adjust at least 2 settings. If you change just one of them you will make your images brighter or darker, depending on which one and which way you adjust it.
Note: You can change all three settings if you like, you would just need to ensure that the total of the changes added up to 1 stop in this example. So if you decrease light by 1-stop by changing your shutter speed to 1/1000th of a second, you could change ISO as an example by 1/3rd of a stop to 500 to increase exposure and then change aperture by 2/3rds of a stop to f6.3 to further increase exposure, therefore increasing the exposure by 1-stop in total to counteract the change in shutter speed.
The variations here would be endless, but what this exercise will do is start to make the relationship between the settings start to make sense. As mentioned each one adjusts light, so if you want the same exposure but need to change a setting such as shutter speed because you aren’t freezing motion as an example, you need to change at least one additional setting to maintain the same exposure.
Depending on the type of photography that you do, there will be some settings that are critical for you to achieve the results you are after.
As an example if you are doing portrait photography and you want to make sure that your subject is sharp, you will want to use a relatively fast shutter speed, maybe 1/200th of a second. So this would be your locked setting, now you can use Aperture and ISO to make adjustments to your exposure. You can either brighten or darken the image by adjusting one of them, or if you are happy with the exposure but want to play with the depth of field you would adjust both of them to keep the same exposure.
Example in Images
In the two sample images below, I show you how I used this methodology in the field to take this landscape image.
Image 1: ISO 100, Aperture: f16, Shutter Speed 1/8th of a second
Image 2: ISO 100, Aperture: f16, Shutter Speed 64s.
You notice that I didn’t change 2 settings in my camera. I didn’t want the ISO or aperture to change, but wanted to change the shutter speed. It’s actually changed by 9-stops of light, so doubling the shutter speed 9 times. The only way I could achieve this would be to reduce the light entering my camera by 9 stops, and this was done by placing a 9-stop Neutral Density filter on the lens. So by reducing the light entering 9 stops I could increase my shutter speed by 9-stops.
This is what made the relationship between the 3 (ISO, Shutter Speed and Aperture) make sense for me, hopefully it helps you as well.