Light meter to do or not to do…..

I get a lot of questions about this so I decided to would maybe be time to dedicate a blog post to our good friend the light meter.
Yeah you probably already know where I stand in this “debate” that has been raging over the internet ever since we have cameras with the instant polaroids on the back, the light meter has done it’s work and can now be retired is a trend you hear more and more. In this blog post I will “try” to tell you why this is not true and why the light meter is of vital importance for your work, and also share some tips on buying the correct one.


Let’s start simple
Let’s first make sure that the idea that the light meter is something like a voodoo device is out of the way, and no the light meter is also not hard to use or to understand. Even a 12 year old could use the meter and understand what it does. What we have to make clear is that the light meter in fact is a very simple device, it gives you the value of light in a certain situation. I don’t say hitting it for a reason…..


The first option you have with a light meter is incident readings.
These readings are (for model photography) done with the dome, you aim the meter under the chin of the model towards the light source and trigger the strobe. The light hitting the meter will be read and the meter will give you a value, now set the camera for this value and your getting a correct exposure.


Some meters will have a so called spotmeter and some meters will do reflective measurements with for example the dome pushed away (or taken off), check your manual to see what your meter does. With reflective you don’t aim towards the light source but you aim for example to the background, you will get a value and this value will give you the value for 18% gray, in other words when I measure a white background reflective and I get a measurement of F8 and I shoot on F8 the background will be rendered as 18% gray.


Wow Frank, it can’t be that easy?
Well actually it is, but……..
As always there are some buts and problems that CAN appear when you don’t understand how to use the meter, let’s pick some of them and explain what’s going on.


Why measure towards the light source?
There are two opinions among photographers about this.
One will say “Always measure towards the camera”
The other will say “Always measure towards the light source”
As you have read I’m in the last category.
And it’s very easy to explain, and to be honest I really don’t know why the first rule is still taught in some schools and books.

When we measure the light source to set the camera, we need a value of the light hitting our subject. The dome as you can see is round shaped so one would expect that light will hit the dome anytime, but in real live situations this is not true. You can try this very easily at home.
Setup your light behind the camera and mount your meter on a stand, now measure the light hitting the meter.
Now move the light source to a slightly more angled position (but keep the distance to the light meter exactly the same, you can use a string or rope for this), the more you move your light source to the sides the more the meter will “drift” from that first measurement. So in other words the distance is equal but still the meter says there is less light hitting it, this is impossible because the inverse square law dictates that light hitting a subject from a certain distance should remain constant and that only when the distance is changed the light will change…….

Now there will be people claiming that this is normal and one should keep measuring towards the camera what ever I or someone else tell you, for those people let’s do the following test. Instead of mounting your light meter to a stand, change this to a real life model. The first image you shoot is from straight from the camera. Now you take several images from different angles (you move your light to different positions, but keep the distance the same), when you measure towards the camera you will see you have to open up more and more and the skin tone of your model will in fact get lighter and lighter. When we arrive in a 90 degree angle the model will be way too light, and when me move beyond the 90 degree point the meter will give you a result that will probably read EU (not within range).

One could of course argue that this is still the correct way to measure but for me it’s clear as day that my model doesn’t change skin tone/exposure in a few seconds so if my meter tells me she does my meter must be wrong (or I’m using it the wrong way).


18% vs 12% gray
Actually I don’t want to go into this debat but I have to because it’s something that a lot of people will hold against me if I don’t 🙂
According to some 18% gray is middle gray, according to some 12% is middle gray.
The reality is that in MY workflow (ProfotoRGB) and the gamma that belongs to that colorspace when I calibrate my light meter to 18% gray ALL my exposures are spot on, and when I use 12% they aren’t. In reality however this is not a real issue and I’ve seen some very technical papers that claim very simple that 12% gray is middle gray, but I’ve also seen papers on why 18% gray is middle gray. In this topic I would like to RECOMMEND to use 18% gray, but if you find in your workflow that 12% works best, all the power to you…. in the end when we calibrate the meter (more on this later) it should be so that when we use the meter the exposure slider should NOT be touched anymore, this is done in the camera with the meter and in the RAW convertor that slider should remain locked on zero. IF you find the need to change this, you have a problem with your meter or metering technique. (later more on calibrating the meter).


There are so many settings and options, which to use?
Actually this is much more simpler than one would expect.
What you will find in most situations is that you will use the following modes :


Ambiant light (sun)
We use this outside to measure constant light (or in the studio with constant light).
You can select to measure the shutter speed with a set aperture or you can measure the aperture with a set shutter speed.
Understanding how light works and the limits of your camera (sync at 1/125 for example for “big flash”) you can with a light meter very easily measure a scene and determine if you need more or less light from the strobes.

For example.
We measure sunlight hitting our scene at F8 on a shutter speed of 1/125 and we want to fight the sun, we than know that we will need more light on our model, let’s say at least F16 (depending on the level of fighting the sun). DO remember however with this example that when the sun hits the model not straight on but from the side you have to measure towards the sun, and later towards the strobes.
When using flash outside I however always advise to start the shutter speed at 1/60 when measuring. This way you can very quickly take away light by raising the shutter speed to 1/125 for example. When you want to use flash as fill start measuring at 1/125 and you can get more ambiant light by lowering the shutter speed. This sounds difficult but when you start playing with strobes and ambiant light it will all become very clear quickly.


For strobes there are often 2 settings (sometimes 3 when using radio triggers).
The first is often the CABLE setting.
Connect a cable to your meter and strobe, press the button and the measurement is done. A good solution if you hate your strobes and want new ones, just let someone trip over the wire and voila you can finally upgrade to those great Elinchrom strobes.

The second setting (which I really advise to use) is the strobe without cable.
In this case you press the button on the meter and manually trigger the strobes. The meter will recognise the burst of light and measure this. You can use for example an extra trigger that you carry with you (the same as on the camera). Some people have even build in skyports on the cable release into their meters, but I still just use an extra trigger.


That’s it? is that really all?
Well yes and no (you felt that one coming right?)
The thing that’s really important when using a meter is the setting for the measurement steps. I personally prefer the whole fstops setting. This means that the meter will give me values in full fstops with 1/10 increments. For example F4.3 which means 1/3 stop higher than F4.
Some people will prefer the 1/3rd stop setting which will give you results like F7.1 of F14, this is personal, I know my f stops and prefer the most accurate reading and because most modern strobes can also be set in 1/10th stops I prefer this setting.


Calibrating the meter
You buy a meter and spend app $400.00 on it, so you should be able to use it,….. right?
Nope. Sorry.
This is I think one of the reasons why people don’t “trust” their meters.
The first of course being not knowing how to measure (towards the light source), the second however is that calibration.
What you do with the calibration is making sure that your camera and meter talk the same language. In fact your NOT calibrating the meter itself (that is often perfect) you’re calibrating the combination of meter and camera (and lens). And funny enough it’s VERY easy to do.

Start up the software you do your work in, for example Photoshop or Aperture or Capture One.
Now setup an 18% graycard and light this with a large light source under a straight angle.
Take a shot and import this into YOUR workflow, don’t convert the file, treat it as you do you normal images. Now go to the gray area you measured on and make sure that the values on that area is around 128.128.128 (first do the colorbalance with the colorbalance picker). Don’t sweat it if your not hitting the numbers exact, but don’t settle for 120 or 140 it has to be around 128, the close the better.

When you’re not hitting that point, change the “offset” of the meter.
Start carefully with 1/10 and do the whole setup again (measure the light, change the light to hit your Fstop, and import the image).

It will vary per meter how you can adjust this.
For most Sekonics it’s pressing the two ISO buttons and you can change the offset with the dial.


PANIC MOMENT !!!!! my meter doesn’t have that option, throw it away ?
Nope, although you can’t calibrate it to perfection all hope is not lost yet.
You can of course play with your ISO, let’s say that ISO100 F8 is rendering the values too high.
You can set your meter on ISO80 and do the same measurement again, you will have to lower the light now to hit the F8.
When importing that image you will have to decide which one is closest, in the future you will now that when the camera is set on ISO100 you will have to measure for example on ISO80 or ISO125. Remember those old time photographers that marked some lenses with -2/10 or +2/10 ? they actually did the same when lenses would be darker. Luckily today we don’t have that problem anymore with most lenses.


But Frank, why not just use the histogram?
Sorry to burst your bubble but the histogram on your camera is useless for anything else than just showing off to your friends. Well ok it has some uses but not when we talk about being correct and constant. I can explain this to you with a very simple example.
Let’s take two models, one very light skinned and one very dark.
Now tell me where in the histogram both should be (but tell me exact).
You see ?
The histogram is nice to show you how the tonal distribution of a shot is, but it tells you nothing about if a skintone is 100% correctly rendered, and to be complete it doesn’t even tell you everything about your RAW, the histogram is build from the JPEG tumbnail… if you set the contrast to high it will clip while in the RAW there is still enough white detail, due to the fact that the contrast only works on the JPEG’s and video in the camera.
The light meter will give you an exact value and when the model comes back in 1-2 weeks it will again, and again and again, so whenever you shoot the model the skintone will be accurate for that moment.


Ok so what about using the spotmeter to measure skin?
I’ve heard this before indeed and to be honest for me it’s in the category, not knowing what it does and how to use the meter.
Using a spotmeter on the skin will give you a value where the skin will be rendered as middle gray… and we don’t want this of course.


So when do we use spotmetering?
Spotmetering is without a doubt one of the most powerful tools you can have.
With the spotmeter you can very quickly calculate the backgrounds. Aim it at a background and you will be able to render it white or black…… this is done by a simple rule that for most cameras 2.5 stops over will render something white and 4.5 stops under will render something black. (this will vary when cameras have more dynamic range, for example my MF camera needs 3 stops for pure white). The nice thing about this, is that it doesn’t matter if we use a white or gray background, the calculation is the same.
You can also use the spotmeter very easily to make sure there is still detail in certain parts of the image (shadows or highlights) with model photography you can of course also do this with the incident meter readings, just make sure you keep the dynamic range of 2.5 over and 4.5 under into consideration.


Hummm, I always measure my white background towards the strobes and add…X stops
Well sorry you are wrong, but don’t worry about 70% of the people that use a light meter do this (maybe even more). When you start to realize how a meter works you already know this is wrong. You are in fact taking an incident meter reading in front of a white background, so the meter gives you F8, when you now shoot on F8 the background should be rendered as pure white for the simple reason that this is what the meter does in the incident mode. Of course you can add some light (I mostly advise 1/3 stop) to make sure that there are no light fall off corners or other problems with the background, but adding 2 or even more stops will make the background go “nuclear” and blow out everything in front of it like the sides of your model, remember those lost hairs or very blocky details in the hair ? Well when you use the meter the correct way, it should be possible to see all the hairs on your models arm in front of a white background.


Ok I’m sold now which one to get?
Believe it or not but I’m not (yet) sponsored by any light meter brand so my advise is REALLY unbiased.
I personally love the Sekonic meter.
My own personal favorite is the Sekonic 758 meter. It can store 3 cameras with calibrations and it has a good spotmeter, the meter also supports all the modes I need and it’s a good build device, it’s not cheap but do remember a light meter is the most important thing in my opinion and will survive your camera upgrades and lens upgrades with a wide margin. When choosing a meter do remember that a spot attachment is best when it has a smaller viewing area, I love the 1-2% spots, don’t fall into the trap of the 20-25% reflective meters, when you are in front of your model aiming at the background over her shoulder that one doesn’t bring you far, the 1% spots are awesome for that.

Spot attachement

There are of course other brands like Kenko (Minolta) and Gossen.
I would however always advise to get a meter with a spot option, you can buy an Spot attachment for Sekonic L358 for example but this brings the price very close to the 758. The following meter would be good alternatives in my opinion, but to be honest I would just go for the 758.

Kenko KFM-2100

If you’re on a budget you can also go for the Sekonic 558 which is very good meter, but has to be found second hand online.


For most the light meter is something from the past.
For most the light meter is not necessary
For some, time spend in Photoshop is no biggy
For most the light meter is a device that doesn’t work for their “style”
For some…… the light meter is a tool they can never work without.

We all have heard the remarks that a light meter is “ok” but it doesn’t fit “their” style, or it “limits” the workflow…. to be honest this is total (you know what). When you understand how the meter works, and as you have read in this blog post it REALLY is no rocket science, you have a very valuable tool that can very quickly give you accurate exposures and help you to limit your Photoshop work very much. Just imagine not needing to use the exposure slider, not needing to use fill light because you measured it on the scene and knew you needed to add just a little bit of light in that area…. etc. etc.

And limiting creativity ?
Well no, it gives you more creativity. It will however make sure that ALL your exposures are correct and that you don’t have to struggle to get the “look” of a model consistant over a period of time, when you look at my work I always play with color and with exposures, but my BASE is always the same, what I do after that is a CHOICE instead of a FORCED option, if you know what I mean.

I hope you’re still reading, or already ordering the light meter of your choice.
Trust me…. you will love using the meter and if you don’t get it, or want to ask a question, feel free to do so.

At Photoshop World in Vegas I will be teaching a seminar where there is also some attention to the meter, so check that out.
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