3 : ISO

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Your camera's sensor

This week we are incorporating the third and final element of the exposure triangle: ISO. It's probably the least glamorous setting on your camera, but fear not! We like to think of ISO as the secret sauce. If this is your first time exploring ISO, do not be overwhelmed by the introduction of yet more numbers. As with Aperture and Shutter Speed, ISO settings are just a way of measuring light. Light is what photography is all about, and this is another tool to help you capture your family beautifully!

ISO is the measurement of how sensitive your camera's sensor is to light. All cameras have a base ISO setting (called an optimal setting), for creating images. On Nikon cameras it is usually ISO 200. On Canon cameras it's usually 100. This is the setting at which your camera's sensor captures the crispest image.

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To fully understand your DSLR's ISO settings, it's helpful to go back to the film concept it's based on. ISO was originally the rating given to different types of film. Each frame of film is made of light-sensitive crystals that capture the light that comes through the lens. Film with a low ISO (such as 200) is made of smaller crystals. Film with a high ISO (such as 800 or higher) is made of larger crystals. The larger the crystals, the faster they are able to capture light.

DSLR cameras replicate this effect by grouping pixels on the sensor to capture light. The smaller the group of pixels, the slower they're able to capture light. The larger the group of pixels, the faster they're able to capture light.

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There's a tradeoff...

Taking a picture at your camera's base ISO leads to an image with good color saturation and very little grain, also referred to as "noise". Sometimes there is not enough light to capture a picture at the base ISO so you must increase your ISO setting to allow your camera to be more sensitive to light. The higher the ISO, the greater the ability to shoot with limited light or at a fast shutter speed. Take note, however! Raising your ISO has a downside. As you raise your ISO, your images will degrade and become "noisy". 

Consider Georges Seurat’s “A Sunday on La Grande Jatte”. In this piece of art, tiny dots of paint work together to create a picture. Similarly, in digital photography pixels work together to create a photograph. Smaller dots (or pixels) create a more realistic picture. Larger dots (or pixels) create a grainier effect.

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Working with your camera

  • Camera brands are different when it comes to setting ISO. Some cameras have a button on the back or top of the camera body, others have a dial, while some cameras navigate ISO via the menu screen displayed on the back of the camera. Locate this function and turn it off of "Auto". You will select your ISO setting.

Is there a rule of thumb?

  • Sensor quality varies greatly from camera to camera, so it is impossible to set a guideline for all participants in Shoot Along. Older cameras (more than 4 years old) may struggle at ISOs of 800 or higher.  At high ISO settings they will deliver images with overwhelming noise. Newer cameras with more robust sensors can deliver images at higher ISOs. The rule of thumb is to shoot at the lowest ISO possible without sacrificing shutter speed or aperture.

Find your camera's limits

  • Do you know the ISO capabilities of your specific camera? Some sensors can go further than others in low light or fast shutter speed conditions. Take time this week to objectively test the limit of your camera's ISO setting. Make a note of the setting that introduces too much noise so that you know not to cross this ISO threshold as you shoot.

Here's a typical scenario

You are inside during the day near a window. It is overcast outside but not dark. There is enough light to see comfortably in the room without turning the lights on. Your kids are about to do something photo-worthy so you grab your camera!

Knowing these kids are going to be moving 100% of the time, you set your shutter speed for 1/640th, since this will surely freeze motion. Your aperture is at f/2.8 since this is the lowest that you can go on this particular lens and you want to let in a lot of light because shooting inside is not as bright as being outside. Your ISO is set to 640 from the last time you used your camera. Here's what you get:

Aperture: f/2.8 Shutter Speed: 1/640th ISO: 640

Aperture: f/2.8
Shutter Speed: 1/640th
ISO: 640

Your first shot is too dark. You are going to have to lighten it up. First you think about aperture... you can't lower your aperture any further since it is already set to the lowest f/stop that this lens offers. The next option is shutter speed... 1/640th was your initial setting but you could lower it a little and still capture action without it being blurry. You change the shutter speed to 1/400th. Finally, ISO... you had it set to 640. Raising this ISO will make the sensor more sensitive to light and brighten your image. You change the ISO from 640 to 1250.

Here's what you get:

Aperture: f/2.8 Shutter Speed: 1/400th ISO: 1250

Aperture: f/2.8
Shutter Speed: 1/400th
ISO: 1250

Overall, your image is brighter. There is no motion blur. It's a little grainy but not grainy enough that you have lost important details. It's a keeper!


ISO, Aperture and Shutter Speed

As you capture your family this week you may use the mode of your choice: Aperture Priority, Shutter Priority or Manual Mode. We discourage you from using Auto mode from this point onward. If this feels daunting to you, please try taking it off Auto for at least part of the week with the intention of experimentation, not perfection. We strongly feel that the sooner you try shooting off of Auto mode (and ideally in manual), the sooner you will have that "A-HA!" moment when the creative aspects of photography come alive.

So in summary, it's all about getting the right amount of light to your sensor so that your pictures are not too dark or too light. You are in control. You always have the ability to:

  • Raise or lower the Aperture
  • Raise or lower the Shutter Speed
  • Raise or lower the ISO

Controlling the balance of the exposure triangle is what will make your pictures special.  Practice, enjoy the process, and capture your family!

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Creative Prompts

  • Shoot at daybreak or dusk, when lighting conditions are more challenging and may require you to raise your ISO.
  • Test your ISO limits with a stationary object positioned near a window.
  • Try to capture motion at a high shutter speed inside. Is it possible with your camera?

Share your images!

Have you tried this week's lesson? We'd love to see the results! 

Share an image and get feedback in our private Facebook Group.