So, now we are on the third and final component of the exposure triangle, ISO. As you remember to obtain proper exposure you must balance shutter speed, aperture, and ISO together letting in more or less light to achieve your desired affect. As you may remember besides managing light flow into the camera, shutter speed also affects motion and aperture affects depth of field. So what is ISO and what does it contribute to the image?

ISO manages how sensitive the camera’s sensor is to light. The lower the number, the less sensitive the sensor is to the light and the higher the number the more sensitive. So in bright outdoor environments, naturally your ISO will be a lower number and in indoor or low light environments you will choose a higher ISO to compensate. Also, if you need a high shutter speed (remember a high shutter lets in less light but can freeze motion?) you may decide to compensate for your exposure by increasing your ISO. Remember everything plays together and if you change one thing you must also change another to maintain that balance.

Up until now, you probably have had your camera on auto-ISO. You have chosen the aperture and shutter speed in the previous tutorials and the camera has adjusted ISO for you. Now its time to go into the menu of your camera and change that ISO setting to manual. I highly recommend choosing your own ISO to maintain control of the quality of your image. Quality of your image? Yes, so by increasing your ISO you are making a trade-off. As the camera’s sensor becomes more sensitive to the light, you start to lose sharpness in the image. Noise or grain starts to appear which impacts the clarity of your image. With noise, if you zoom in, the image looks pixelated and textured. Not ideal to say the least. So, as a rule of thumb, you will want to keep your ISO as low as possible while still obtaining correct exposure in-camera. That last part is really important. When dealing with less light, it is better to push that ISO up and simply expose the image properly in-camera than to settle for an under-exposed image (unless you are choosing to do so stylistically). The reason for this, is if you are planning on increasing the exposure on a dark image with post-processing, you are actually going to add more grain to it than if you had just used a higher ISO and exposed it properly to begin with. So choose your ISO wisely but do not be afraid to push it up if you need to.

How high is too high? Good question, and frankly, there is no hard fast answer as it really depends on how your camera handles low light and what your tolerance for grain or noise is. Higher end cameras have sensors that can handle higher ISO settings with less impact to noise whereas a lower end model may show noise sooner. Simply put, your tolerance may vary camera to camera. With this in mind, you will have to play around with your camera to find your own acceptable tolerance. Its a little bit of trial and error to find the balance of what your camera is cable of versus your acceptable limit is for grain. So don’t hesitate to play around with this setting. Take a few pictures at varying ISO’s then load the picture onto your computer and zoom into 100%. Compare the pictures. What do you think? On my Nikon 810, I start to get really uncomfortable with noise around an ISO of 3200 (even though my camera can technically go a lot higher). However, on my Nikon 5200, I would get pretty uncomfortable at about 800. That being said, even with my 810, to maintain super sharp photos, if I have to push my ISO up past 800 I will typically pull out my flash unit. But, then there may be situations where you choose a higher ISO on purpose and noise is not an issue. Perhaps, you are shooting for a black and white image and you want that raw grainy feel…or you are shooting in low light and you want to capture the integrity of the image without supplemental light like my Christmas Tree Magic pictures. Its up to you, there really isn’t a right or wrong here. Its about what your camera is capable of, what you are comfortable with, and how you decide to accomplish your vision. Its about your preference and your style. And keep in mind your tolerance for higher ISO numbers may vary depending on your equipment. When I first upgraded my camera from a crop-sensor (DX) camera to a full-frame (FX) camera I immediately noticed a difference in how the full frame camera handled higher ISO settings in relation to noise. Basically, on a full-frame camera, the sensor used to detect light is larger yet its still retains the same number of pixels. This makes for a better quality photo with a higher ISO value than a crop-sensor. But, wait … don’t just run out and buy a full-frame camera. A great deal of know-how can make for better pictures more than a fancy piece of equipment but not much know-how. In other words, you can take great pictures with the DSLR you have right now!

For stylistic and environment purposes, I usually will set my aperture and shutter speed first and then “fill” my exposure with my ISO (unless I am using flash as my “fill” then I will maintain a low ISO and use my flash to compensate). Which, is kind of what auto-ISO does on your camera. However, I want you to use manual ISO so you are aware of it and how its going to affect the quality of your image. With the camera set to auto-ISO you could get a grainy photo and not even realize that your ISO was sky high! Out of sight, out of mind, right? By setting ISO yourself, you are choosing the outcome with intent.

Key Learning

• ISO is the third component of the exposure triangle and determines how sensitive the camera’s sensor is to light
• The lower the number, the less sensitive the sensor whereas the higher the number the more sensitive
• There is a trade-off when you increase your ISO as you also increase grain in your image
• It is better to expose an image properly in-camera and use a higher ISO than to pull up exposure in post on a dark image

Practice

Set an object outside where there is plenty of light, expose it properly (use your histogram and meter as a guide). Use whatever mode you are comfortable in…but make sure your ISO is set to manual. You will likely be either in shutter priority or aperture priority or push that dial to manual! I recommend manual so you can ensure that your aperture and shutter speed settings stay constant if at all possible. Take the picture. Now take that same object and move indoors, expose it properly and take the picture. Again, leave the shutter and aperture the same. You should be solely making your ISO adjustments based on your ambient light. Where was your ISO in the bright outdoor light? Where was your ISO indoors? I would guess quite a bit higher. Take both these images and load them onto your computer, zoom in to 100%, and notice the difference in sharpness and grain. What do you think?