Exposure Triangle – “ISO + Aperture + Shutter Speed”

Exposure Triangle - ISO, Aperture, Shutter Speed

At the very basic level – all a camera does is capture the light.

In the process of doing so, sometimes it lets in a lot of light – while sometimes it does not let in sufficient light. How much of it is important is completely dependent on the situation. Getting in the perfect amount of light is the first thing every cinematographer (videographer) needs to think about.

You might wonder – “Hey Rajit, I am doing fine using AUTO mode on my camera”

That’s a valid statement – in fact, today’s camera have a pretty impressive AUTO settings (exposure, focus etc.) Light meter might work for you 🙂 But it’s always better to shoot in MANUAL mode to get the most out your camera and the circumstance. Here are few reasons why you should always be striving to shoot in manual mode:

  1. The camera does not know your end-vision. What kind of photo/video are you trying to shoot? Is it a silhouette or a portrait? Sure, you might change your color profile, white balance and all – but the camera will never know your end goal – the picture you have clicked in your mind.
  2. Although the camera’s light meter is precise, it’s not 100% accurate. Because it treats every situation in a similar manner.
  3. The camera does not know what to compensate over others. For example, you might want a bokeh effect (or blur background or shallow depth of field) at the cost of shutter speed – only you’ll know that, not the camera.

When we customize all 3 exposure settings (Aperture, Shutter Speed and ISO) together, we can create the desired effect and the kind of photo that we want to click.

Vertex #1 – Aperture:

Simply put, an aperture is an opening (or hole) through which light travels.

The main purpose of having an aperture is to control the amount of light that passes through the lens and then reaches the sensor. The major function of a lens is to focus the light from the source to the camera. Aperture plays a big role in this process.

Aperture - for Shallow Depth of Fied

Allowing just the right amount of light is really important in photography. If you overdo it, your image will be over-exposed and will seem blown out. Do the opposite, and you’ll under-expose the image (means the image will seem darker)

… aperture is the first door through which the light passes.

Thanks to aperture – now we can create a shallow depth of field – which means we can blur the background to drag the focus to our subjects. It’s the effect that most of the photographers look for when starting out.

Here’s an example: (this is me on the image 😃)

In this image (portrait kind of image), the focus is on me (or the subject) and the background is blurred out a bit to drag the focus on me. Hence, we can see the people in the background – but not with sharp focus.

This is the effect that aperture creates.

Aperture is measured in terms of f-stops.

Basically, the higher the f-stop number, the lesser the hole opens. And, lesser the hole opens, the sharp the depth of field will be (everything will be in focus). Hence to create the blurred background, the f-stop should be as low as possible.

In portrait, you might want to use aperture as low as f/4, f/2.8 or even lower.

While in landscape, you might want to use aperture as high as f/11 or even higher with higher ISO.

… all depends on the situation and the moment you’re trying to capture.

Vertex #2 – Shutter Speed:

After the light passes through the aperture (of the lens), it passes through the next door – that is shutter (of the camera).

Now you might wonder …

… why is there 2 settings (or the ways) to let the light in when one can do the job? Well, it’s for a creative reason. While aperture is responsible to create the shallow depth of field, shutter speed is responsible to freeze the motion. This comes in quite handy when we are shooting the movements.

Shutter Speed is the measure of the time it takes for the shutter to open and close it. The faster the shutter speed is, the better the motion freeze the camera does – because the shutter only opens for a short time. In case, you shoot the motion with slower shutter speed, the image will get blurry – because when the subject moves before the light gets in completely.

Basically, this is the idea:

  1. Faster Shutter Speed = Freeze the motion
  2. Slower Shutter Speed = Blurs the action

Shutter Speed is measured in terms of “1/number” seconds.

Basically, higher the number – the slower the shutter speed is. This can be confusing for the beginner – since it’s the opposite because the shutter speed is measured in terms of 1/number.

Let’s assume that you want to record a flying bird …

In this case, you’ll want to use a faster shutter speed (1/1000) to freeze the motion of the bird. Since the shutter opens for a very short period of time (in this case), it captures the bird for that short time period.

Possible shutter speed usage:

Shutter SpeedUsage
1/1000 (or faster)Freezes the motion of the birds and faster objects
1/500Freezes the motion of vehicles (cars, bike etc.) and runners
1/250Freeze slower motion (eg: people walking)
1/80Regular Footage – does not freeze
1/8 (or slower)Blurs the flowing-water or the peoplle walking

Summarizing till now:

You can think this way – aperture is mostly related to Space dimension (how wider it opens) and shutter speed is mostly related to Time dimension (how faster it opens).

Vertex #3 – ISO:

The camera has a light sensitive material – “sensor”.

ISO = light sensitivity value. ISO is particularly valuable in the low light situation – where you have opened the aperture as widest as possible and shutter speed for the longest (where it does not get blurred), the only option you have is to increase your ISO.

… but there’s a downside to it.

When you start increasing your ISO value more than a certain point, it will start to see grains (or noise) in the photo. Hence – the general rule is to use the ISO value as low as possible.

Possible ISO usage:

ISO ValuePossible Situation
Daylight / Outdooor100
Studio Set-up400 – 800
Low Light Room1600

In Conclusion

You’re always in control of your exposure.

No matter how your lighting is, or how your composition is – if your exposure sucks, then your whole photo or video clip will suck. Because, that will be the first impression.

Hence please try to take care of the exposure while shooting !!

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Posted by Rajit Chaulagain

Rajit Chaulagain (Chief Executive Officer @ Swopna Digital) writes about SEO, Filmmaking, Blogging, Animation, VR (Virtual Reality), AR (Augmented Reality), and many other exciting fields.