What is ISO & How Does It Work?

Image of professional camera settings Sony

Whether photography is a passionate hobby or a professional job, when we all start out with our first cameras we are all a bit clueless. Generally, we start in “auto” mode and just start snapping. Eventually, with time and experimentation, we graduate to using manual modes to help capture the scenes as we see them by adjusting settings.

Switching to manual mode (M), or any other mode outside auto, can be intimidating. There are so many different settings, dials, buttons, and scales to use that one can be too overwhelmed and switch back to auto mode. We want to take things one step at a time and break down the important stuff. Before we jump into the importance of ISO in manual mode, let’s go over some of the basics first.

different camera modes and settings

Different Digital Camera Modes & What They Do

  • Auto – Usually found with a green icon “A” on your camera, auto mode is perfect for when you are just getting started. It will choose all the necessary settings for you to get a clear and well-balanced image when you’re shooting a photo.
  • Program Mode or “P”– This mode is a more advanced auto mode that can be used when you want the exposure to be selected automatically by your camera, but other settings like ISO and white balance can be adjusted by the user. This may be a good transition mode to start using if you feel intimidated by the manual mode (below). This will allow you to start getting a real feel for what your camera can adjust and how the photo can be composed differently, without sacrificing all your camera‘s settings.
  • Aperture Priority or “A”– This mode is what controls your aperture for your camera. Aperture can be thought of as the depth of field. You can correlate that to the phrase “bokeh.” Bokeh is when the subject (usually a person) is in clear focus and the background is smooth, blurry, or out of focus. When you are in aperture mode, you select the aperture you desire: generally ranging from f/2.8 to f/22. The lower the “f-stop” or aperture number, the more focus on the subject this is good for portraits or photos with a subject. The higher the “f-stop” or aperture number, the more everything will be in focus overall this is a good tip for landscapes or cityscapes.
  • Shutter Priority or “S”– This is the option you will want to turn to for those dreamy night photos of the stars or the smooth surfaced look of crashing waves against the beach. Also, this is a great mode for capturing all those waterfalls in a smooth cascade. When you are selecting the speed of the shutter (how long it will stay open to capture light), the camera will select the aperture automatically to capture the right exposure. While in shutter mode, you also have control of the ISO, which will be helpful when you want to darken or brighten your image based on your shutter speed you are selecting all the while, your camera is automatically selecting the aperture for you.
  • Manual or “M”-The name explains it all. This is the mode that puts the photographer in the driver’s seat. You are responsible for selecting the shutter speed, aperture, and ISO. This can be very daunting for beginners, but like we always say if you don’t try and start experimenting you won’t know how to use it. When you first start to tackle using the manual mode on your camera, we suggest just doing it in a controlled environment where you aren’t too concerned about “what” you’re capturing, but rather “how” you’re capturing it. That way, you can take your time to adjust and change various settings and see how they result in your photo.

So Now We Know About All These Modes…

What Is ISO in Photography?

We mentioned ISO a few times above when describing the different camera modes that are at your fingertips, but reading about what they do and knowing what ISO has to do with it are two different things.

We know there are various levels of photographers out there from beginner to advanced, but no matter what your skill level, it’s still important to understand the elements that go into your photo being captured.

Getting back to the basics, ISO is the setting that determines the brightness of a photo.

As you increase the ISO number, your photo will be brighter. This is one of the most important settings when capturing the night sky because it allows you to brighten the dark sky and capture all the stars or Milky Way in much brighter settings. But, if you bring the ISO up too high during a photo, you may start to see a grainy texture or “noise” in the photo. A good rule of thumb only raise your ISO when your aperture or shutter speed cannot capture the brightness on their own.

With digital cameras, it’s easy to adjust the ISO based on your environment. There is typically a large range of ISO values on your camera from ISO 100 all the way up to ISO 12,800 (or greater). Because the ISO setting does affect the clarity of the image, it is recommended to keep it as low as you can to capture the dynamic range of the color in the photo.

high ISO image for night photography
Using High ISO – Photo by Virginia B – @BueWho

Times You May Want to Raise ISO:

  • Night Photography – In order to capture the low-light of the night sky or the details of the Milky Way, you may want to try a higher ISO to capture all the twinkling stars.
  • Indoor Settings – When taking photos indoors (and you don’t have the use of a flash) it may be a good idea to raise the ISO to brighten up the photo a bit without sacrificing the shutter speed.
  • Instagram Only? – If you are capturing a photo that you plan on only sharing in a small space like Instagram or a small thumbnail, you can generally get away with using a higher ISO.
  • Vintage Look – If you are going for a specific style of a photo, you can increase the ISO in a situation to give you a grainy look in your photo. You can increase that look when editing as well.
  • Freeze Motion – If you are trying to capture a fast subject with the freeze frame, increasing your ISO will be helpful to capture the image clearly while having a fast shutter speed.
lower ISO image for color and clarity
Using Low ISO – Photo by Virginia B – @BueWho

Times You May Want To Lower ISO:

  • Using a Tripod – When using a tripod you can get away with a lower shutter speed as opposed to handheld, therefore you can lower the ISO and capture a clearer image.
  • Large Depth of Field – If you are trying to take a picture of a landscape or cityscape with a wide field of view, you can higher the aperture on your camera which can, therefore, bring in more light which would allow you to lower your ISO for better image quality.
  • Have A Flash? – If you are using a flash to light up your subject that will allow you to use a lower ISO.

Things To Keep In Mind

Not all cameras or lenses are the same. So be aware of the aperture settings your different lenses have, what ISO range your camera has, and how you will be editing your photo. All camera settings are different, so some may not be applicable for your camera setup.

Also, when previewing your photos on your camera‘s LCD screen, consider that it will look MUCH different once you have it on your laptop or desktop. Keep in mind the noise reduction settings your camera may have and also the editing software that can reduce the noise that a high ISO may produce on your image.

Overall, remember that ISO can allow you to adjust for faster shutter speeds, smaller apertures, and capturing dark scenes. As always experiment, play around with different settings, and find your style.

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