Light quality & quantity of light – essential knowledge

We all know that light is the key ingredient to a beautiful photograph, but we need to understand light to use it for maximum impact. More specifically, we need to know about the characteristics of light – light quality and quantity of light – and how to use them in both natural light photography and flash photography.

It doesn’t matter how gorgeous your subject is, if you don’t understand light, your photo won’t be gorgeous. Well, you could get lucky, but that’s not easily repeatable.

The first trick to mastering natural light is to stop taking it for granted.

Because we’ve spent our whole lives surrounded by natural light, we don’t give it the kind of appreciation it deserves. The attention it needs if we’re to be great photographers.

Diffused direct sunlight for soft light quality

A beautiful sunset is great and impossible not to notice, but what about all the other times of day when natural light is doing different and interesting things?

As with all things to do with light, the characteristics of light is a big subject, so I’ve split it into two parts. In this article we’re looking at the first two characteristics:

  • Quantity of natural light
  • Quality of natural light

So, let’s get into it!

1. Quantity of light

When we talk about the quantity of light – natural light or flash – we are literally talking about how much light there is. It’s not often that anything is so straight forward in photography! But of course there’s more to it than that.

High quantity of natural light at midday

Lots of light, shooting in direct sunlight at midday, meant a fast shutter speed and low ISO to allow for a wide aperture.

So, the quantity of light, or the amount of available natural light, affects your exposure settings. If you’re familiar with the exposure triangle, you’ll know this.

Whether you shoot in manual mode, or leave it partially to your camera to decide the exposure by using aperture priority or shutter priority, the quantity of the light is the starting point for determining exposure settings.

Photographing with a wide aperture on a bright, sunny day, means your shutter speed will have to be high and your ISO as low as you can go. On the other hand, freezing motion in low light, means having to crank up your ISO and open up your aperture.

Even if you hand everything over to the camera and let it decide with program mode (try not to do this) or auto mode (definitely don’t do this), this characteristic of light, light quantity, influences how your camera decides to expose the image.

Speaking of which, there’s a “correct exposure” for all circumstances.

What’s a “correct exposure”?

This is the one your camera will want to make, but can get wrong. In other words an exposure where the highlights are not overexposed and the shadows are not underexposed. You have detail in both.

You might decide that you don’t want a “correct” exposure. You might want a very bright image with blown out highlights, or a very contrasty image with extremely dark shadows. That’s also okay, if it’s done intentionally. Your exposure decisions around your creative intent for the image are entirely up to you.

Whatever you decide, you’ll need to know how to measure light quantity.

How to measure the quantity of light

There are two easy ways to measure the amount of available light, and therefore the exposure. Use either the light meter in your camera, which measures reflected light, or a handheld light meter, which measures the light falling on a subject.

On a bright sunny day you could also dial in your exposure settings using the sunny 16 rule – it’s a great way to get into manual mode.

Something to bear in mind while we’re talking about measuring light… The image on your camera’s LCD looks different depending on how you tilt your camera. So, if you’re relying on looking at the LCD to gauge your exposure, how can you be sure how accurate it is?

Learning to read your camera’s histogram will help you to determine the correct exposure, but it’s not perfect. The ultimate failsafe method for an accurate exposure is to use a handheld incident light meter.

However you decide to establish your exposure settings, it’s the quantity of light that has the greatest impact on your exposure. So it helps to know the best time of day for photos outdoors.

Is it:

  • A bright cloudless summer day
  • An overcast winter day
  • Night time

Also, are you in:

  • Direct sunlight
  • The shade
  • A thick forest
  • Indoors

Low quantity of natural light late in the day

Shooting in low light, just after the sun had dipped below the horizon, required a high ISO, wide aperture and slow shutter speed.

Our eyes are much better at seeing than our camera. While you might be able to see perfectly fine in thick woodland on a really overcast autumn day, your camera might not. In fact, it definitely will struggle with the low light quantity for photos in bad weather.

2. Quality of light

When we talk about light quality, we don’t necessarily mean good or bad light, but rather the effect of the light on the subject. The feel of the light – how hard or soft it is.

When we consider the hardness of light, we’re looking at the shadows. More specifically, contrast and the transition from highlights to neutral light to shadows.

  • Is it a slow and gradual transition with soft shadows (soft light)?
  • Or is it quick and sharp transition with harsh shadows (hard light)?

What role do shadows play in photos?

Your decision to include, exclude, maximize or minimize shadows affects the contrast in the image and contrast impacts the mood of a photo.

Do you want dark and moody, light and airy or somewhere in between?

Direct sunlight with harsh shadows light quality

The only difference between this photo and the one at the start of this post is that here she is facing into the direct sunlight, so there are harsh shadows on her face. In the photo at the top of the article, she is facing away from the sun and her hair is also blocking the sun from reaching her face directly. As a result, the quality of the diffused light is soft and more pleasing.

Manipulating light quality – how to get hard or soft light

Your light source affects the quality of light in two ways:

a) The bigger the light source, the softer the light

Well, with natural light, the light source is the sun, so there’s no changing its size.

While the sun is huge, it’s really far away, so it’s actually a small light source from a photographer’s point of view. This is why direct sunlight causes harsh shadows.

That leads me to the next way to manipulate the quality of light.

b) The closer the light source is to the subject, the softer the light will be

Again, there’s no way to get the sun any closer than it already is. It’s not like it’s a flash that you can move closer or further away as you wish. This applies to direct sunlight.

In a moment we’ll look at photographing indoors in indirect light and this is where you can use distance to control the quality of light.

Before we move on, there is something you can do about light quality for direct sunlight. You can photograph at different times of day:

  • At midday the sun is overhead and the harsh light casts hard shadows.
  • At the start and end of the day golden hours, shadows are softer, because the sun is near the horizon. Sunlight has to travel through more atmosphere, which acts as a diffuser. It spreads out, makes the light source bigger and softens the light.

Speaking of which…

Diffusing direct sunlight

You can’t change the size or proximity of the sun, but you can alter how light reaches your subject. Unless of course you’re a landscape or wildlife photographer etc. Portrait photographers can manipulate the quality of the light reaching their subjects by using diffusion.

When we diffuse light, we soften the light quality. This results in a slower transition from highlights to shadows, i.e. softer shadows. 

How do you diffuse direct sunlight? 

It’s quite simple – diffuse sunlight by blocking it. Here are three ways to block natural light:

Position your subject in the open shade of a building or a tree, i.e. facing away from the tree or building.

Or hold something over your subject so that they are in shade, if there are no trees or buildings around. A handheld diffuser is perfect for this. They’re cheap, lightweight, pack up small and you can get them in different strengths.

A 2-stop diffuser blocks out more light than a 1-stop diffuser.

Another way to achieve soft light quality is to photograph your subject indoors using indirect natural light from either a window or an open door. Obviously, even if you’re indoors and the sun is shining straight in and directly onto your subject, you’ll still have harsh shadows.

Soft light quality of indirect natural light indoors

She’s facing a large floor to ceiling window, just out of view to camera right, with indirect light flooding in.

Going back to what I said on the size of the light source, indirect natural light coming in through a big opening will be much softer than through a really small opening.

So, bearing this in mind, to soften or harden the light, change the size of the aperture through which the light travels.

In other words, open the door or curtains. 

You can test this by flinging the curtains wide for one shot, then drawing them in, nearly closed, for another. You will of course have to adjust your exposure settings to handle the lower quantity of light.

The last point on using indirect light indoors is to remember that the closer your subject is to the open door or window, the softer the transition will be from highlight to shadow.

Let nature diffuse the light

Natural light diffusion outdoors comes in the form of clouds. If it’s a cloudy day, nature has kindly provided a diffused light and turned the sky into a giant softbox. This is a great time to photograph people outdoors!

Now you’re ready for the next part in the series on the characteristics of light – find out more about how light works.

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Meanwhile, if you have any questions about light quality or quantity, let us know in the comments.

Also, I love good news, so if my natural light tips have helped you to understand quality of light and quantity of light, share that too.

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