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From the very first minute you dabble with DSLR cameras you will have no doubt heard these three terms. You will have heard a lot about how these three settings can make or break an image. But how do you understand them yourself and how do you know what situations to use them in and how they can be used? Read on as this article will teach you everything you need to know about ISO, Shutter Speed and Aperture.

Quick Summary

Before I fully explain what ISO, Shutter Speed and Aperture are, I will quickly give you a rundown and summarise it for you.

ISO is a number that measures the sensitivity to light of the camera sensor. The higher the ISO number, the more sensitive your camera is to light.

Typically you increase the ISO number in low-light situations where you need to brighten the image a little, but if you increase the ISO number too much it will result in a grainy picture!

For example, you would use an ISO of 100 in daylight conditions. You would probably use a higher ISO in a low-light scene or at night-time such as ISO 800 or even 1600, though it depends on the quality of your camera sensor and how much grain and noise you are willing to tolerate in your images.

Aperture describes the opening of a camera lens in which light is let through the lens straight into the camera sensor. The smaller the Aperture number is, the larger the Aperture and the more light is being let through the lens and into the camera sensor.

A larger Aperture, such as F/1.8 will result in a brighter image with a shallower depth-of-field while a smaller aperture, such as F/11 will result in a darker picture and a picture with a deeper depth-of-field.

Shutter Speed determines how long the camera sensor is open for while capturing a photograph. The longer the shutter speed is open, the more light will be let in and the blurrier the image will be.

A longer shutter speed is ideal for shooting light-trails or for letting more light in at night-time or in low-light conditions where you need more light being let into the camera sensor.

A longer shutter speed will blur the motion while a shorter shutter speed will freeze the motion, such as water droplets in the air or your dog jumping for a ball.

The longer the shutter speed, the lighter and blurrier your image is and the shorter your shutter speed, the darker your image will be and the motion within the image is more likely to be frozen properly.

If you would like to see a more detailed explanation of all of this and see how each settings should be used properly in different situations, then read on below as I will go into much more detail on all of these topics below.

What is ISO?

ISO 200 example

The ISO settings indicate to the camera user how sensitive the camera sensor is to current, available light. The lower the ISO number, the more natural light you will need in your scene in order to get a well-exposed image.

However, if you raise your ISO setting you will be able to get a brighter, better-exposed image in less-than-ideal conditions.

But despite what you might think, you can’t just increase the ISO as much as you want so you can brighten up any scene, unfortunately.

When you increase the sensitivity to light by adjusting the ISO, you are also introducing grain and noise into your shots, too. Grain and noise can ruin an otherwise great image and it is hard to remove either of the two using Photoshop or Lightroom.

This is why we have a number system to help us out when working out what to set our ISO level at.

Most modern DSLR cameras have their lowest ISO setting at ISO 100. ISO 100 is ideal for bright, daytime shots where there is loads of light in the scene and not too much contrast in the scene, either.

From about ISO 100-400, you will notice very little, if not any noise in your shots and it is in this ISO range you should be using to shoot most of your pictures.

This is especially true if you are shooting in broad daylight where there is really no need for you to bump up your ISO.

When you start shooting your images in low-light or night conditions, you will start to see the issues with increasing your ISO above a certain level.

For example, if you are trying to freeze motion (such as people walking or a car) in a night-time shot, you cannot increase the shutter speed to let in more light as this will result in blurry image and the motion in the scene will not be shot correctly.

What you would have to do instead is bump up your ISO. But you need to be careful when deciding how much to increase it to. For most DSLR cameras, you will start to see grain and noise creeping into your shots (day or night) at around ISO 1600, though this may be a higher value for full-frame sensors and smaller for action cameras like the GoPro or a smartphone, both of which have considerably smaller sensor sizes.

In this scenario your best bet would be to bump up your ISO to either 800 or 1600 and then underexpose your shot to allow you to have less grain in your image.

This is a great idea as you can still get the shot you want but you can reduce the amount of noise that may be visible in your image.

What you would have to do next is increase the shadows in Lightroom and recover the finer details but this may not be viable if you have little experience in editing photos.

In this case your best option is to sacrifice a little of the photo quality and end up with some grain but you will get a much brighter image with a more even exposure.

When should you raise your ISO?

There are a few example of situations where raising your ISO makes sense:

  • When hand-holding a long lens. For example, you are using a telephoto 70-200mm lens in which case raising your ISO will be necessary in order to get a sharp shot.
  • When using a flash would create an ‘artificial’ look or it may ruin the feeling of the photo
  • To freeze motion shots when taking them handheld
  • For astrophotography. You ideally need an ISO of 3200 or above in order to get enough light into the camera sensor within a 20-30 second shutter speed/exposure

These are all great examples of when raising your ISO level is probably the best thing to do but be careful when you decide to increase your ISO.

Whenever you are shooting images, try your best to shoot with the lowest ISO possible. Try and increase your Aperture and Shutter Speed values as high as you can first and then raise your ISO level afterwards.

But if this not possible for some reason (eg. you need to keep the shutter speed as low as possible because you want to freeze the motion in a scene), then try this the opposite way.

In this case you should raise the ISO as high as you are willing to tolerate for your own personal taste and then adjust the Aperture and Shutter Speed accordingly. Then see if you can lower the ISO even by just a little to reduce the amount of grain and noise that will be present in your shot.

But all in all, the ISO level is very important when taking photographs and you should pay attention to the ISO number on your viewfinder very carefully.

What is Aperture?

F/1.2 aperture camera lens

The easiest way to explain Aperture is by comparing it to the human eye. The pupil in the human eye controls how much light is let into further in the eye.

The Aperture effectively does this but instead of an eye we substitute this for a camera sensor.

The smaller the Aperture number, the more light is let into the camera sensor and is then captured. The larger the Aperture, less light is then let into the camera sensor.

We measure the Aperture on a camera by using something called the F-Stop Scale. The F-Stop scale is a set of numbers that usually range from F/1.8-F/22, but this varies depending on the lens being used.

Aperture affects Depth-Of-Field

You also have to take into consideration that the Aperture number on your lens can also wildly affect the depth-of-field within your shots.

A wide-open F-Stop of F/1.8 will typically let in a large amount of light compared to a narrower Aperture. F/1.8 Aperture is commonly the widest Aperture on many lenses, such as a 50mm lens or a 70-200mm lens. At the same time it will lead to a shallow depth-of-field which means that you will have a soft, blurry Bokeh in the background of your shot.

This Bokeh can be great in certain situations, particularly portrait and product photography. But it has it’s downsides, too.

If the Aperture is too wide, it can result in the depth-of-field becoming too narrow for you to be able to keep your entire subject sharp. In this case, you should use a smaller Aperture value, such as F/8 or F/11.

Speaking of F/8 and F/11, these two apertures are considered to be the best ‘middle’ apertures for when you want to let in a lot of light but you want a deep depth-of-field with no bokeh in the background.

A great example of when to use F/8 or F/11 is in landscape photos where you want all or most of the photo to be in focus but you also want enough light to be let into the sensor at the same time.

Some good examples of when to increase you Aperture include:

  • To get the desired ‘Bokeh Effect’ (which involves a blurry background with the subject sharp in focus)
  • To allow more light to hit the sensor (particularly useful if you do not want to increase your ISO level and run the risk of getting grainy or noisy shots)
  • To make the subject stand out more from the background (useful if you have a complex/busy background like a busy street or a lot of lights at night)

All in all, the Aperture is an important setting but should only be adjusted once you have decided on what your base ISO is going to be.

Only after you have set your base ISO should you worry about your Aperture. From then on you should either set your Aperture based on the availability of light within the scene you are trying to capture or for artistic purposes (such as how much Bokeh or Depth-of-Field you wish to have in your photos).

What is Shutter Speed?

shutter speed settings and options

Shutter Speed is the time in which light is allowed to hit the camera sensor. Pressing the shutter is like opening and closing your eyes except with a camera you determine how long the shutter stays open for and in that time you light is hitting the camera sensor.

The amount of time the shutter needs to stay open in order to let in enough light depends on a wide range of factors. These factors include:

  • What your ISO level is
  • How much motion is going to be in the scene you are trying to capture
  • What artistic effect you are trying to create (think light-trails or long-exposure shots of cars going past)
  • Are you using a Tripod or not?
  • How steady are your hands (how steady can you keep your hands when taking the shot)

Your Shutter Speed is measured in fractions of a second for most types of photography. The main exception to this is long-exposure photography, where Shutter Speed is measured in whole seconds instead.

When looking at a camera viewfinder or viewing the EXIF data in post-processing software, the shutter speed will typically look like 1/1000 or 1/350.

For example, a fast shutter speed will be needed to take a shot of a sports game or fast-moving motion like skiing or water spraying in the air if you want to be able to successfully freeze all of the motion in your shot.

For these kinds of shots, a Shutter Speed in the range of 1/500 – 1/1500 seconds will be your best choice for successfully freezing the motion within a scene.

For shots where there is less motion or you want to add blur to your shot, you should use a shutter speed within the range of 1/30 – 1/60. This is great for getting a panning shot of a passing car or bus and can be great if you want blur in the background of a shot like this, too.

Shutter Speed also affects your exposure as well as the longer your shutter is open for, the more light will be let into the camera sensor. If the shutter speed is set incorrectly, this can result in you getting either an underexposed or overexposed image (though slightly underexposing your image can be a good idea if you will be editing your image).

When exposing your shot, you should always try to keep your ISO level as low as possible and then set your shutter speed to expose your image properly.

But in low-light scenes this can be more difficult, particularly if you are trying to take pictures that have a lot of motion in the scene. It is in these instances where raising your ISO will be the best course of action.

When, where and how should I use these settings then?

All of that information was probably a lot to take in, so I will sum it all up for you now and tell you what the most important points are.

The ISO number indicates how sensitive the camera sensor is to current light:

  • For most daytime shots, the ISO should be between ISO 100 – 400 to ensure there is as little grain and noise as possible
  • At night-time or in low-light situations you should try your best not to raise the ISO above 1600, UNLESS ABSOLUTELY NECESSARY! To avoid this, try increase your shutter speed, aperture or underexpose a little and edit your photo in Photoshop or Lightroom
  • ISO is best raised for scenes where you need a fast shutter because you are using a long lens or there is fast-paced motion in the shot and you cannot get a better exposure by using any alternatives like raising the aperture or the shutter speed

The Aperture is like a pupil in the eye. It determines how much light is let through the lens and into the camera sensor:

  • Using a wider Aperture such as F/1.8 is great for low-light conditions or for when you want to get a blurry ‘Bokeh’ effect, but it may mean you are not able to get all of your subject sharp in the image
  • Using a narrower Aperture such as F/11 or F/8 can result in more of your image being in focus, which is great for landscape shots! But it can also mean that not enough light gets into your shot and then you end up with a very underexposed shot!
  • Aperture is best raised for artistic purposes such as having a shallower depth-of-field or for allowing more light into the sensor if you do not want to raise your ISO

Shutter Speed determines how long the shutter in your camera sensor is kept open for:

  • Using a longer shutter speed will allow more light into your shot, which can be a great alternative to bumping up your ISO levels, but this will not work if you are looking to capture motion as the longer shutter speed will blur out all of that motion
  • A very long shutter value such as 30s or 15s can be great for getting long exposures or astrophotography
  • You should decide on your shutter speed once you have set your base ISO and then you can set the value depending on whether you are trying to capture a long-exposure shot or expose for the highlights or shadows in your image.

Did this article help you?

I would really appreciate it if you could comment below what you learned from your article and give me a shout if you are still unsure about anything. Feel free to leave your thoughts down below!

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Joel Oughton is the Creator of Photoaspire. He likes to write about anything photography related and is more than happy to help out others with any photography-related issues

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