What is ISO and How Do I Choose the Best ISO?

A common question for first time digital SLR (DSLR) owners is what is the ISO setting on your digital DSLR camera and how do you use ISO? When it comes to digital camera specifications in general, this particular concept can be quite confusing for some (it was for us when we first started, at least). ISO stands for International Standards Organization and it a standardized scale to measure sensitivity to light. The scale begins at 100 ISO, which means not so sensitive, and ranges to 1600 ISO depending on your camera, which means extreme sensitivity to light. To simplify, ISO determines if your image will be light or dark. So, how do you know when to set which setting? Firstly, understanding that there are three major settings to consider when taking a photo, shutter speed, aperture, and ISO, will help you determine which ISO setting to choose. When you begin to understand these three pillars and different lighting options, it will all click, but for now, let’s dive deeper into ISO and how to set your ISO camera setting properly.

How to Choose the Correct ISO Setting?

Increasing your ISO number will result in brighter photos but can also create a lot of grain or noise. If you are unable to work with the lighting with your aperture or shutter speed settings, then increasing your ISO will help brighten the photo. All cameras have a different ISO range, which is known as “ISO speeds”, that you are able to work with. For example, there is ISO 100, ISO 200, ISO 400, ISO 800, ISO 1600, ISO 3200, and even an ISO of 6400. An easy tip to remember is that when you go up a notch in your ISO setting you are doubling the brightness of your photo. Although, sticking to your “base ISO” or lowest number ISO is usually a good idea because it is your highest quality image setting. There is no noise or grain.

How to change ISO on your camera depends on the camera, but it is suggested to change the setting in Manual Mode instead of Auto Mode. For most beginner DSLRs or starter mirrorless cameras, you will find a Menu or Quick Menu, where you are able to quickly adjust the ISO, or most DSLRs have a dial or wheel that has already marked ISO settings to choose from. Definitely familiarize yourself with quickly adjusting ISO so when you are out and about taking photos, you won’t miss a moment to capture.

Hand Holding vs. Tripod

A few things to consider when understanding how to use ISO, is are you hand holding the camera or using a tripod to take photos? If you are going to use a tripod, you can most likely use a slower shutter speed, so your ISO will be lower.

Subject in Action

If your subject is moving, you want a higher ISO. If your subject is still, then you can lower the shutter speed and ISO.

Depth of Field

You can increase your aperture if you are not shooting a big depth of field. Allow light to enter the camera and lower your ISO.

Artificial Light

If you are using a flash or light, more light will most likely enter your camera which will allow you to decrease your ISO.

Grain or No Grain

This totally depends on you! If you want more grain or noise in your photo, then kick up your ISO!

Enlarging Images

If you are not going to blow up your image, then you can have a higher ISO. It is only until you enlarge the image that you can notice the noise and grain, so take this into consideration before adjusting your ISO for the shot.

Understanding ISO

Once you have gotten comfortable with the above tips, you want to know the difference between shutter speed and ISO setting. So, what is the difference between ISO and shutter speed?! Pretty much, the higher the ISO, the faster the speed. If you have a higher ISO setting set, then the shot will be taken much faster because it is sensitive to light. BUT, high ISO settings can cause a grainier/noisier shot. And like mentioned above, you won’t really notice the grain or noise from your camera, but once the image is blown up or enlarged, it is definitely noticed. Try to stay away from a high ISO and try decreasing the aperture instead.

A few ISO tips that are recommended include:

1. If you are shooting on a rainy or cloudy day, go for a ISO setting of 400. If you cannot get the shot without a blur, start to increase the ISO from there. But start at 400.
2. What about when you shoot at night? Great question. A base recommendation would be to a higher ISO, like an ISO of 800. Make sure your aperture is low and that there is some street lighting out.
3. If you want to shoot indoors without a flash, well then start at around an ISO of 800.
4. Action shots that you just want to capture with fast-moving subjects? Keep the ISO high. Although, this all depends on what type of image you want to capture. Are you trying to just getting the shot no matter the quality? Or are you trying to capture a high quality image with no grain or noise? Consider that question when shooting action shots.
5. What if I want motion blur? If you do want a blurred image, turn off Auto ISO and lower your ISO to the lowest number. Increase your aperture, too. This should give you the blurred/noisy look you are aiming for.
6. Want to capture a subject but blur the background? Use the largest aperture possible to blur the background of your subject (or what’s behind the subject).

So, if you are trying to find the right ISO, how do you know when to increase or decrease ISO? If there is not enough light and the camera is unable to capture the image quickly, then increase the ISO. If you are indoors, like mentioned above, you can use a high ISO number without a blurred or out of focus image. Some cameras have Auto ISO which is great because if you are in a low light environment when shooting, it will capture the shot automatically. If there is a lot of light, lower the ISO. Easy, right? You’ll get the hang of it!

What camera mode should I use? If you are a beginner, then shoot for the Aperture Priority mode. This will set your lens aperture and automatically adjusts the correct shutter speed. There is nothing wrong with using the Auto modes on your camera, that is what they are there for! But it is great to understand as a photograph what your camera is doing and adjusting while you are shooting. The Auto ISO feature is an excellent way to allow your camera to guess what the right ISO should be in various lighting surroundings.

Another great tip when beginning to understand ISO and your general camera features is learning when to use flash or when to increase ISO. Usually, it just depends on what you are shooting. If your subject is super far, your flash might not reach, so upping your ISO will help capture that shot. But if you are shooting a building, for example, you should not use flash because it will not reach the entire building. Higher your ISO.

Also, understanding that all cameras are not created equal when it comes to ISO capabilities is very important. This is why photographers tend to “update” their camera bodies. Some higher end cameras can reach up to 250,000 or more in ISO setting. Others can only reach up to 6400. Keep this in mind when you are shopping for the perfect camera. If you want a larger range when it comes to ISO, then shop smart.

(TIP: Is there a way to reduce noise and grain in post-production? Yes! There are many tools for adjusting the noise on an image. For example, if you are using Photoshop CC, there is a tool called “despeckle” and it is a super simple and effective way to reduce grain or noise.)

Concluding how to choose ISO

In conclusion, a general rule of thumb when trying to find ISO is try to keep your ISO as low as possible, without a blurred or out of focus image. Other tips, if its sunny out, set your ISO for 100 or 200. If it is overcast and dreary outside with little light, use an ISO setting range from 400-800. During the evening or at night, increase your ISO setting to 1600 or so. There really isnt a perfect setting for the “perfect” shot. It all depends on SO many factors when shooting. You really are just trying to balance your exposure the best way you prefer and for the shot.

So, between aperture, shutter speed, and ISO, it is a constant balancing act when photographing, but once you understand these features and really get the hang of it, it’s super simple and so much fun to adjust and play around with!