Take great pictures of your kids! Part 3: ISO & The Exposure Triangle

How is the practice coming along? Do you enjoy creating dreamy, blurred backgrounds with a wide aperture? Have you frozen a moment in time with a fast shutter speed? It’s time to add in the last point of our triangle and see how they all work together.

In the film days, ISO was your film speed, but in the digital world it is referring to the sensitivity of the image sensor in your camera. ISO can range from 100-6400 or even higher depending on how advanced your camera is. The LOWER your ISO, the LESS sensitive your sensor is to light. The HIGHER your ISO, the MORE sensitive your sensor is to light. How will this effect your photography? The sensitivity of the image sensor directly effects the amount of noise (grain) produced in an image. This is neither good nor bad. Some people strive for no noise, while others add grain to images in post processing. It is simply personal preference.

In the following image, I was forced to use an extremely high ISO in order to use a high enough shutter speed to freeze the motion of my son. You can see considerable grain in the image, and my way of dealing with it was to convert the image to black and white.

ISO 12800 f3.2 1/160
ISO 12800 f3.2 1/160

This time I was shooting outside on an overcast day. I had plenty of light to work with so I was able to set my ISO much lower and still properly expose my image. You’ll see that the colors and shadows are crisp and clean.

ISO 400 f/2.8 1/320
ISO 400 f/2.8 1/320

In the following set of images, I kept my shutter speed and aperture settings the same, only changing my ISO settings. This will illustrate the increasing sensitivity of the image sensor.

ISO compare

Generally speaking, you want to use the lowest possible ISO to properly expose your image. Lower ISO settings will result in clean, crisp images with little to no noise. However, sometimes we are required to raise our ISO higher in order to use faster shutter speeds in low light situations. Let’s say your image requires a shutter speed of 1/1000 and an aperture of f/5.6 and needs to be properly exposed, but there is very little light. Raising your ISO will increase the sensitivity of your image sensor, increasing the amount of light it is able to record even though there is very little being let in, thus allowing your to properly expose your image. Just be aware that you may need to embrace the grain that comes along with ISO. Compare the following images. The first was taken at ISO 800 and retains most detail leaving you with a crisp image. The second was taken at ISO 6400 and you will notice more grain in the image, especially in the shadows.

ISO 800 f2.8 1/60
ISO 800 f2.8 1/60

 

ISO 6400 f2.8 1/500
ISO 6400 f2.8 1/500

 

When shooting outdoors in full sun, ISO 100-400 is a good starting point. ISO 400-800 will be appropriate for pictures indoors with good window or overhead lighting. Low light situations will require ISO 800-3200 in order to obtain proper exposure. With practice, you will get to know the lighting in your house and yard. You will begin to intuitively know that the morning light in your kitchen allows you to shoot with a lower ISO, while afternoons in your basement force you up to ISO 3200.

Now, how do we tie it all together? My go to strategy depends on my subject. If I am shooting my kids running and playing, I determine my shutter speed first. I know that in order to freeze their motion, I need a shutter speed of at least 1/250. I then set my aperture based on how many kids are in the frame, usually somewhere between f3.2-5.6. Now I check my light meter and adjust my ISO to properly expose my image. (Remember that you want to get your light meter to zero as a good starting place.)  If I am shooting a large group of people, I know that I need my depth of field to be larger. In this situation, I would start with my aperture somewhere between f/4.0-6.3, then set my shutter speed to at least 1/125 (higher if there are little ones), and finally adjust my ISO in order to expose properly.

Exposure Triangle

At first, it is challenging to think about all three points of the triangle at one time. Don’t be discouraged. Be patient with yourself, and with a little practice, you will be capturing cherished memories for your family!

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