About the light meter in a quick overview

On August 12th I joined Scott Kelby during his great “Light it, Shoot it, Retouch it” tour.
If you didn’t already see it, and it’s close to you, make sure you check it out… You’ll love it.
Anyway, during my piece of the seminar I choose to do the high contrast light setup using a deep octa and strip light, during the setup I of course also talked about the use of a light meter and explained some of the theory behind it, however after the seminar I got so many questions from people who never used a meter to people who had problems using one that I decided to dedicate a blog post to it, because really honest… using a meter is like the simplest thing you can do within photography.

Voodoo or not
You know there are two camps among photographers when it comes to the use of the light meter, I always call them Camp light meter and Camp no light meter (yeah I know it sounds cheesy), the funny thing is that when you talk online about the meter it’s often a case of black and white, in other words you love it or you hate it, there hardly is any middle ground. Now I have dedicated a lot of space to the use of light meters, and I’m afraid a lot of more space will be spend in the future because somehow the most ridiculous reasons to use or not use a meter are still being spread, let’s do a simple point by point system explaining the use of the meter and making some things clear.

It’s hard to use and it takes a lot of time
Sorry but people saying this should not call themselves Photographers. We all know how to use a camera that is WILDLY more complex than a light meter. In fact the light meter is just a very simple tool. And no it does not take a lot of time to use (it saves you a lot of time).

So where does this story come from ?
I really would not know, but I will tell you very simplistic how a meter can be used in for example model photography.

Step 1:
Aim the meter with the dome towards the light source (under the chin of the model, or close to her body depending on where you want the measurement to be accurate) and trigger the strobe.

Step 2:
Set the camera to the value the meter says.

Step 3:
There is no step 3….. now don’t tell me that was difficult 😀

Ahum Frank that’s REALLY it ?
Uhu, yes, sorry.
Now let’s look at some of the reasons why people find it hard to use a meter.

Option 1:
The don’t have a clue how their light works.
This is probably the biggest reason, if you set your light wrong and you meter on the face of the model while the hotspot is on her chest your image will look incorrect. However what people forget is that the exposure on the models face will be correct. Still often the meter is being blamed and people go back to the “when I can see it, I can correct it” method.

Solution 1:
Master your lights…. yeah I know sounds logical indeed but it’s the truth.
When you know how to set your lights and you know what happens when you change the lights metering it will be accurate. Let’s take for example a spot you aim at your model, with the meter you can set it 100% accurate without ever seeing the light. You use a so called “cross metering” (well actually I call it that). Meaning you first measure on the face of the model (aimed towards the light source) and let’s say that gives you a value of F8.0 you now know that if the chest meters F11 you’re wrong so you have to relocate your light, in other words, the face should be the highest value (UNLESS you want the “focus” on another part of the body of course). By metering in a cross (middle, left, right, up, down) you can actually visualize the circle of light, and also 100% accurately know where the light will loose too much power to render for example the dress.

WOW wait…. you know before shooting the light fall off ?
YES, but more later.

Option 2:
People don’t know how the meter is used.

Solution 2:
I could say RTFM but I won’t, because it’s really just very simple.
I advise people to set the meter on a measurement of 1/10th stop.
This means that the meter will meter the light and give you a value of a FULL F-stop and something.
The full F-stops are :
2.8 – 4 – 5.6 – 8 – 11 – 16 – 22 – 32

The numbers behind the full stop are 1/10th stops.
Meaning for example that a reading of F8.3 means you have to shoot on F8 and add one click on the camera (because the cameras today are set in 1/3rd f-stops). It’s really that easy. Most people however will know on which F stop they want to shoot and adjust the lights for that, so let’s say you have a reading of F8.3 and you want to shoot on F8 this would mean you have to lower the strobe 3/10th of an F stop (on Elinchrom this means going 3 clicks down). And yes that’s actually all there is to know, there is no more voodoo or things to understand, it’s REALLY that simple…..

We can go deeper and speed up our setups however
Understanding LIGHT, and I really mean LIGHT and not the meter is of course essential to our photography, let’s be frank with each other a Photographer paints with light so he/she should actually really understand what’s going on. To my surprise however a lot of the photographers out there don’t really have a clue about light, it’s like a painter that doesn’t know anything about his paint, canvas or brushes and mixes water paint with oil based paints.
A few lines above I said you could know the light fall off by using the meter.
This is not a voodoo quality of the meter however. We know that our cameras have a limited dynamic range, and we can test that. However first we have to know one thing about our basis, and that is :

18% gray
Most of our calculations are based on 18% gray. We also call this middle gray, or in Photoshop 128.128.128 (but that’s not important now). We also know that one stop of light is double the amount of light (or half). This would give is very quickly the following dynamic range…..

black is app 4.5 stops lower
1.1% gray is four stops lower
2.2% gray is three stops lower
4.5% gray is two stops lower
9% gray is one stop lower
18% gray is middle gray
36% gray is one stop higher
72% gray is two stops higher
white is app 2.3 stops higher

This very simple theory gives you enormous speed when setting up light and using a meter, and DO remember this is theory about light and in fact has NOTHING to do with the meter, the meter is just the tool to METER the theory.

Let’s say we set our spot (strobe) on our model and the face is properly lit at F8, we now have to make sure that to keep detail in the dress/clothing we cannot drop more than let’s say 4 stops on the light, would we drop more we would loose detail, you will have to take into account what kind of clothing she is wearing of course, a white dress will keep detail longer than a black dress. But there is even a way to meter that very accurately.

Incident vs Reflective
Not all meters have this option, but if you buy a meter REALLY get one that does have a 1-2 degree spot option, you will love it.
When we normally meter our model we use the dome pointed towards the light source, we call this incident metering, in short it measures the light falling on our subject and gives you the value on which to set the camera to render your subject accurate (when metered correctly of course, meaning as close to the subject as possible).
With the spot metering (reflective) we get a different value from our meter.
We now aim at the subject (most of the time a background) and the meter gives us the same kind of value, let’s say F8. However when we would set the camera for this value and we would shoot our background it would not be rendered correctly, but it would be rendered 18% gray. Now this is an incredibly powerful tool when you understand how to use this.

When you look at the schedule above you can see that if we would add 2.3 stops to 18% we would render something pure white, but when we decrease the power by 4.5 stops (or more) we will render that subject totally black…. you feel the powerrrrrrr ?
With this method you can set your backgrounds in seconds (yes you read that correctly literally seconds), you will NEVER EVER blow out details in the skin or hair from your models again when using white backgrounds, you will also never find that your background is not 100% black and you need to photoshop it black (which can make ugly marks and visible retouching)

So when a model meters F11 when using the dome (incident)
Your background should read F22.3 to render it white (although in all honestly I always add at least 1/3rd stop to make sure you don’t see wrinkles and light fall off), or below F2.0 .5 to render it 100% black. And yes it’s really that easy.

Now we also are at that point why some people find the use of a meter difficult and decide to do it by eye or using the back of the camera (which is a HUGE mistake), this all sounds very technical and for some people it’s too much to remember at once or to understand when reading it quickly, however one should realize that only the step 1 and 2 at the very top (remember those ?) are the use of the light meter in every day use…. everything that follows after that is understanding LIGHT and NOT the meter…. however when you understand light you can use the the meter to bring this into work.

Frank let’s be honest, isn’t it just easier to look at the screen ?
Trust me I’m always honest about these things and I say “NO” really in capitals.
First off all the back of the camera is useless, what you see is based on a JPEG thumbnail which use settings in the camera, your RAW however doesn’t, so the display never shows you how the final result will be.

But even when shooting tethered it’s not 100% accurate, especially laptop screens and most LCDs are very prone to the viewing angle, just for fun project a very dark image and move your head to the left and right and top and bottom, on most screens you will see a difference in the brightness of the blacks,  seeing details that are not seen when looked at the screen from the proper angle. Also remember that although the fill slider is a very powerful tool, you are in fact also introducing artifacts like noise and sometimes even halo’s into your image, and that is never the idea of course.

However we could go on and on and on for ever, there are always people that will know a reason why not to use a meter, so I will say it very short and hopefully wake some people up…. why spend a minute too long in Photoshop on EVERY image and run the risk of loosing shots or detail while with a meter you can within seconds see what’s going on and know when to add or subtract light ? I really don’t see the argument 🙂 but that could be me. When you use a meter it will give you a number, dial the number in your camera and you’re spot on…… learn a bit more about light and you will learn how to quickly measure for absolute black and white and everything in between…. and yes I REALLY setup up a 100% lit white background in seconds without blowing detail, and I can do it with any background (as long as you give me enough power of course). But the real kicker…. I can also do it outside when I don’t have the aid of modeling lights etc.

Questions
Of course you are free to ask them here, but here are already a few I know will come:

I don’t have a spot/reflective meter how to do the white background ?
Very easy, you have to make sure it’s a white background.
Go to the background, aim towards the light source and if the model reads F8 make sure the background is on F8.3, in fact in a perfect world the background would need to be on F8 and it would be white (remember incident gives you the value to actually render the correct brightness), but in reality you need to add just a little bit more because there is no perfect background, there is always some light fall off, some wrinkles etc.
Also sometimes you DO have a reflective meter but you just don’t know it, read your manual and look for reflective, in some meters you can slide away the dome and use it as reflective.

My camera is that a reflective meter ?
Yes, you are understanding it I think.
Remember that when you shoot snow it always turns out too dark, or when you shoot a nice skyline it’s always too bright ?
That’s were a reflective meter goes “wrong” but now that you understand how light works you can adjust this very easy, for snow just add xx stops, and for the skyline just lower xx stops… how much ? well sorry I can’t tell you that, I always tell my students (and I use this myself) to guess how much of the area is white or black and if a lot is black or white go closer to the 2.5 over (white) and 4.5 lower (black), but if there are a lot of lights in the skyline or a blue sky above the snow go a bit lower/higher. And yes if you use a meter with spot you could meter this very accurate, and yes you can use your camera for this, although it’s a bit of a hassle.

Set the camera to spot metering and frame as much as possible of what should be black or white in the center and meter the light, now press the * (exposure lock) for snow add let’s say 2 stops and for the skyline let’s take away around 4 stops (which would mean going to manual because most cameras don’t go that low), now frame the shot and use the exposure compensation for 2 and -4 (manual) and shoot, it should be pretty good.

I’m always told to meter towards the camera
I know, but trust me… that’s wrong.
When you meter towards the camera you’re metering light that comes from the camera… and although some light setups work great that way, most don’t especially in todays fashion work. You can do the test very quickly yourself. Setup your light straight above the camera on let’s say 2 mtrs, now meter towards the camera and it should be perfect, however now start moving the light more and more to the sides (keep exactly the same distance), when you meter towards the camera the value will go down, however when you meter towards the light it will stay constant, and that’s correct because the inverse square law dictates that light at the same distance will stay the same in value, and also when you shoot your model you will see that metering towards the light source is the only right way.
I hope that with this “small” blog post I have explained some things about the proper use of a meter and triggered you to dive into it and maybe buy your first meter ? or start using the one you have.

Outside use of the meter
This can be tricky.
You always have to remember that the meter will meter both ambient and strobe.
Normally this is shown in a percentage, what you have to realize is that to make a proper exposure from what you have in mind you can’t always trust that percentage or even the reading the meter will give you. For example if there is a lot of light and the strobe is way underpowered the meter will not give you the correct reading (ambient light wins), so take note of that. Also remember that it’s very important which way you point the meter, if you meter straight into the sun the percentage will be different than when you have the sun in the back. So when you want to create let’s say a day to night image from different angles and you only concentrate on let’s say 90% strobes you will get widely different results when you meter in a setup that faces the sun or where you meter with the sun highlighting (accenting) your model. What you can do in these cases is use the spot metering function and meter the sky and take the same difference in stops as you did in the shot before.

When outside and metering ambient only also take note that in this case you DON’T have to always point towards the light source, in this case the sun. Let’s say we are highlighting a model with the sun hitting her from behind and we want a proper exposure on her face, some people will now point the meter towards the sun (metering the only light source) and make an exposure for that, this however will not give you what you want. In this case it’s better to point the meter towards the camera and meter the ambient light (day light is everywhere) and set the camera for that specific exposure. It might sound weird because in the studio and with strobes I tell you to NOT do that, however when you look at the way light behaves outside it’s actually very easy to understand.

Outside light is coming from everywhere and most of the time in exact the same values, so it makes perfect sense to meter towards the camera, however…. not always. When you are using for example reflectors from the side I would highly recommend to point towards the reflectors IF they give you more light than the available light, UNLESS you want to use the reflectors to be used as accent lights and they are supposed to be higher than the main light.

Yeah I know it sounds confusing, but in reality it really isn’t.
You always (and I mean always) have to focus on which side of the light you want to be accurate, if you want the face of the model to be correct straight on, meter (outside) towards the camera because the light is everywhere. If you are using a reflector to light the models face from the side and you want that side to be correct and the rest to be darker, metere towards the reflector. If you want the sun behind the model going through her hairs and concentrate on that meter towards the sun… if the model is blond or very light meter with a spot towards her hairs and make sure that you open up NOT MORE than 2.3 stops (above that the hairs will loose detail).

You can also use the spot meter for metering skies and shadows.
Meter the white fluffy clouds and make sure your shooting not more than 2.3 stops wider to keep detail in the whites, same goes for the shadow areas, meter the shadows and make sure you are not more than 4.5 closed to keep details in the shadows. If you experience a scene that has more dynamic range you will have to : accept this, add extra light via a reflector or strobe, or shoot HDR.

As you can see the meter can be confusing if you look at everything I told up here, however I also hope that you will see through this and realize this is ALL just light behaviors and has in reality nothing to do with the meter itself, the meter itself is and will always be a “dumb” device that just gives you values that YOU have to understand and incorporate, so don’t be scared off by all this text and think you need to understand this to use a meter, you need to understand this to solve lighting problems, and to solve those you do NEED a meter because that will give you the values you are looking for.