Metering 101

Light meter at “zero” means a good picture. Right?

Wrong.

Shoot something black, filling the entire viewfinder with that object, and make sure the light meter points at “zero” as you are pointing at the subject (use the viewfinder!). Take the picture.

You get this:

The histogram shows why this is bad:

A histogram of a black object should peak on the left (the dark side).

Now do it again, with the light meter pointing at –2 (minus 2):

Perfect. Look, the histogram is right for this type of scene:

The moral of this post:

  • “The meter displays zero” does not equal “this will be a good picture”. It merely means “this will be a mid-grey picture, neither dark nor light”.
  • “The meter points to minus” does not equal “this will be a bad picture”. It merely means “this will be a dark picture”.
  • “The meter points to minus” does not equal “this will be a bad picture”. It merely means “this will be a dark picture”.

And there you have it. Now you understand the camera’s built-in light meter.

 

 

 

 

 

Exposure metering basics

In the continuing series on flash and its complexities that I started yesterday, time for the next basic subject. And that is “metering” and “exposure compensation” while not using a flash. (Yes, to understand flash you need to first understand non-flash exposure basics. So bear with me in this series.)

What does your light meter do?

When you press down the button half way while pointing at your subject, you activate the light meter – and the camera now does one of two things:

  1. If in manual exposure mode (M), it merely shows you a light meter in the viewfinder. You can now adjust aperture, ISO and/or shutter speed, and when you achieve “meter in the middle” this means “well exposed (if the subject is mid-grey)”.
  2. Or when you are in an automatic mode (P, A/Av or S/Tv), the camera itself sets aperture and/or shutter to make the meter go to the middle. The picture will therefore be well exposed (if the subject is mid-grey).

Let’s look at that qualification: “well exposed (if the subject is mid-grey)”.

  1. Your light meter -  a reflective light meter – is calibrated to give you the “zero” reading when your subject is exposed to look mid-grey, i.e. neither very dark nor very bright. That’s just how it was decided it should work. Because most of the world is like that.
  2. So as long as what you are shooting is neither dark nor bright, all is well. Aim at zero and shoot, and all well.

So what if you are shooting dark or light subjects?

Let’s start with what happens if you are aimed at a dark subject:

  1. Setting the meter to zero gives you a light grey subject – not a black subject!
  2. So you need to somehow make the meter point at minus – say, minus two for a black subject.
  3. That way the subject will not look grey, but darker.
  4. Which is good – because since it is darker, it needs to look darker!

And what if you are aimed at a bright subject?

  1. Setting the meter to zero gives you a light grey subject – not a white subject!
  2. So you need to somehow make the meter point at plus – say, plus two for a totally white subject.
  3. That way the subject will not look grey, but lighter.
  4. Which is good – because since it is lighter, it needs to look lighter!

Your light meter does not know whether you are shooting a coalmine in the dark (total black)  or a snow-hill on a bright day (total white). It cannot know. So you will always need to compensate for this.

How do you adjust?

If you are using manual, you adjust aperture or shutter or ISO until the mater moves to the desired setting. If in an automatic mode like P, Tv/S, or Av/A, you use exposure compensation (“the plus-minus button”) and set that to minus or plus – the camera now adjusts aperture, shutter or ISO.  So the adjustment

Real-life example 1:

Here, a viewfinder-filling black bag with the camera on “P” (or on “M” where we make the meter go to “zero”):

And here, the same viewfinder-filling black bag with the camera on “P” with exposure compensation (the +/- button) set to minus two (or on “M” where we make the meter point at -2):

“But making the exposure go to minus two will make the subject all black, Michael”.

Yeah. And that is what we want, since it is black!

Real-life example 2:

Here, a viewfinder-filling white sheet of paper with the camera on “P” (or on “M” where we make the meter go to “zero”):

And here, the same viewfinder-filling white sheet of paper with the camera on “P” with exposure compensation (the +/- button) set to plus one (or on “M” where we make the meter point at +1):

“But making the exposure go to plus one will make the subject all bright, Michael”.

Yeah. And that is what we want, since it is bright!

Conclusions:

So, no magic. Just logic. Simple:

  1. If a subject is lighter than average I need to make sure it shows as lighter than average, and if a subject is darker than average I need to make sure it shows as darker than average.
  2. I can make these adjustments in manual mode by changing aperture/shutter so that the meter does not point at zero.
  3. Or I can make these adjustments in automatic modes by using exposure compensation (and now the camera does exactly the same: it adjusts aperture and/or shutter).

In the next while, more – but first, start by understanding this. A good way is to use manual mode for the entire day tomorrow, and only available light.

Have fun!

Beginners’ rules of thumb: Exposure

When shooting in auto modes (P, A/Av, S/Tv etc), you will need to adjust exposure often. How? Quick rules of thumb for you today.

What to adjust. If the non-flashed part of your pic (what’s lit by available light) is too light or too dark, use exposure compensation (the plus/minus symbol). If the flashed part of your picture (what’s mainly lit by your flash)  is too light or too dark, use flash exposure compensation (the plus/minus symbol with a lightning symbol next to it, or adjustable via the menu).

How to adjust. If what you see is too dark, use plus. If what you see is too light, use minus.

How to predict. When shooting a very dark subject or scene (coal mine), you will need minus. When shooting a very light subject or scene (snow scene), you will need plus.

 

High-key black and white

One of my favourite photo styles is this: high-key black and white, against a simple white background. This reduces the clutter to a minimum and starkly emphasizes the subject. Like in this image from the 20 November Mono, Ontario all-day workshop:

Tara, by Michael Willems

What I would say if I were to discuss this:

  • The image screams out “black and white”.
  • Clothes (white)  and wall (white) both disappear. I like the emphasis this gives the subject and the pose.
  • I like the 1970s feeling. I added a little grain to this image in Lightroom to emphasize that.
  • Slight, very slight, soft beautiful shadows are important.
  • Light is simple: one flash bounced behind me.
  • Of course you use exposure compensation and the histogram to check your exposure. But you knew that. Hit the right side (just).

Try a portrait like this! All you need is a white wall, a camera, an on-camera flash, and a model in white.

Confusion reigns…

…but I am here to help you sort it out.

I hear a lot of beginning (and some advanced) students who confuse white balance with exposure.

This confusion is not surprising, since both have something to do with “this picture of a white wall, say, is not white enough”, and they both occur together very often.

So here’s the summary:

  • White balance is about the colour (it ought to perhaps be called “colour balance”).
  • Exposure is about the brightness.

So ask yourself what you mean when you say “that white surface is not white enough”!

  • If it looks too yellow, say, then it is white balance you need to adjust (the WB setting on your camera).
  • If it looks too dark, it is exposure (the +/- setting, “exposure compensation”).

And of course since they occur together,you may well have to do both. Get the colour right first, then the exposure.

Confusion lessened?