The Light Meter, How Do You Read It?

Saturday 14 September 2024, 16:32 by Frank Doorhof | 4,255 views | 15 comments

This article was translated from Dutch with the help of AI. Read the original.

A light meter is a tool for measuring your light. Some photographers think it is something from the past. Others do not 'need' one.

And some people never use one. I am a big fan of using a light meter. In this article, I explain why and how to read a light meter.

Light meters are cool

Let's start with a bold statement: I know that for many people, light meters are not the first thing they think of when they start with photography.

But that is not right. I could say that it is one of the most important parts of your kit.

Why is the light meter so important?

First of all, we need to realise that as humans we only see three colours. We call these colours the primary colours, Red, Green and Blue.

We also have secondary colours, Cyan, Magenta and Yellow. All colours are connected through the blackbody curve (white points for colour temperature) and determine the colour space.

So how do they determine the colour space, you may ask?

A good question, actually. All colours within the colour space have three coordinates, x, y and Y. Hue, Saturation and Luminance.

If we want accurate colours in our photographs, I think it is clear that we need to make sure the colours are captured as accurately as possible when taking the photograph.

We have two tools that work together for this. The first is the colorchecker (I will write another post about that in the coming days) and the light meter.

The colorchecker is used to calibrate the colours in your RAW converter, but to get the colours (x,y) right, we also need to get the Y right, and that is where the light meter comes in.

It is actually super easy

Sometimes I feel a bit like the light meter helpdesk, with all the questions about using light meters. And most problems are caused by not understanding the meter, so let's dive in.

Let's make one thing clear first. It really is super easy.
Let's take a look at the display.

On the display you can see the shutter speed: 1/125s, ISO 400 and the aperture f/8.0 (4)
And this is where things often go wrong. Many people will now set the camera to f/8 at ISO 400 with a shutter speed of 1/125. And... Well, the images are overexposed. So how is that possible when using a light meter?

Well, because there is one extra number that is really important, and that is the small 4.

It is all in the details

When we look at our camera, you probably know that you can change your aperture in 1/3 stops. On most flashes, you will find one of two options, also in 1/3 or even 1/10 clicks. But do not confuse the two with the aperture on your camera.

The settings on your flashes have nothing to do with what you see on the meter. It is simply the output power, and there are also settings such as 2.8, 4.0 or 5.6 that are there simply because... Well, because those values exist.

So how do we go about it?

When your meter shows f/8.0 (4), this means that the meter is showing f/8 and 4/10ths. If you have flashes that can be adjusted in 1/10 increments, you can simply lower them by four clicks and you will probably read f/8.0 afterwards (if you have good flashes).

If your flashes can be adjusted in 1/3 stops, we need to improvise a little. Lower the flashes by one click and the meter should now show f/8.0 (1). Now it is a matter of moving the light a few centimetres further away and it will show f/8.0

Now I have to be honest, for 1/10 I do not really move my lights, but if you really need to be very precise, it works brilliantly.

Let's give it a try!
Here we see f/5.6 (7)

We have a few options:
1. We can go down 7 clicks on a flash with 1/10 adjustments and get f/5.6.
2. We can go up 3 clicks on a flash with 1/10 adjustments and get f/8.0

1. We can go down 2 clicks on a flash that works in 1/3 adjustments and move the light slightly for f/5.6.
2. We can go up one click on the flash and end up at f/8.0

1. Set the camera to f/8.0 and lower your aperture by one click for f/7.1.
2. Set the camera to f/8.0 and increase your ISO by 1 click (ISO is also set in 1/3 stops on most cameras)

The great thing is that once you know how to read the light meter, you can change settings very quickly. Do you have problems calculating settings such as ISO, shutter speed and the relationship between the aperture?

Do not worry, when using a meter, you can simply change one setting and the other settings will change.

In other words, if you have misjudged the exposure and get a reading of 1/125, ISO 400, f/8.0, and you need a faster shutter speed, you can simply change the shutter speed, ISO and aperture until you see the settings that will work. You do not even need to take a new reading.

Are light meters only for flashes?

So is a light meter only useful when using flashes? No, absolutely not. A light meter can be used in different configurations, just like your camera.

You can use it to determine your aperture or shutter speed and, of course, to play with your ISO. It is like the 'Swiss pocketknife' for every situation

OK, I am sold, which light meter should I buy?

It is no secret that I love the Sekonic brand, but in essence you can also buy another brand. First, make sure that your light meter is compatible with flash. Very old meters often are not.

Also make sure that you decide whether you need an incident meter or want both types (reflective and incident).

Incident versus reflective

When we look at the difference between the two, the easiest way is to compare the reflective meter with how your camera works. It gives you the value for 18-12% grey.

To use this, meters often have extra attachments (spot meters), or on the more expensive models the spot meter is built in.

Personally, I would strongly recommend buying a meter such as the Sekonic 758 or 858 with a very narrow spot meter built in, around 1 percent is ideal for most people.

You can also buy attachments for some other meters, as mentioned, but I do not want to fiddle with attachments that can get lost, so the 758/858 would be my choice if you also want to be able to take reflective readings.

But do you need it?

That is a good question. The main meter we use light meters for is the incident light meter. This means that you hold the meter in front of the part you want to illuminate correctly, and the meter gives you the correct value.

Now you might say... why would I ever use a reflective meter if I only get 18 percent grey from it?

GREAT question! We often use reflective metering to make white backgrounds 100 percent white, rather than 98 or 110 percent. This prevents light loss and shows all the detail in clothing and hair that you would lose if you 'overexposed' the background too much.

Or we make sure that certain areas are 100% black. But you can also calculate the fall-off of the light.

Now I have to be honest. I mostly used the reflective meter outdoors, to calculate the output of my flashes for creating day-to-night images, adding fill light and everything in between. But with modern cameras, there is a very cool trick for this.

Is the EVF a replacement for the light meter?

Yes, you read that right, the electronic viewfinder (EVF) can replace the 'reflective' meter. But only in certain circumstances. For example, when you are on location and want to create a great day-to-night effect.

Simply set the electronic viewfinder to emulation mode and set the shutter speed wherever you want. Start playing with the aperture and ISO and just look through the viewfinder. Let's say you love f/8, 1/125 and ISO 100.

Now all you need to do is set your flash to f/8.0, for which you still need an incident meter (to do it quickly and correctly).

How to read a light meter, conclusionReading a light meter is super simple once you understand the extra numbers and how they work with your camera and flash.

The benefits are immense: you can work much faster, visualise and set up location shoots within seconds, and amaze your client by taking the photograph straight away, something you see less and less, instead of constantly trying.

If you look on Marktplaats, you can probably find plenty of meters, but if you want to buy new, something I do recommend with precision instruments, I would look at the Sekonic range, such as the Sekonic 858 (my meter) or the Sekonic 758. But the Sekonic 358 is good too.

These are examples of the meters I have owned over the years, but they also have some really good alternatives such as the 508, 308x, 478, and so on.

Visit Sekonic.com for more information about the different types.

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