Environmental Report #2

The white “cave.” A similar setup was used for the dark environment.

The white “cave.” A similar setup was used for the dark environment.

What a difference the space makes

In our previous episode I compared various modifiers used in a very dark environment which limited the light being able to bounce off of surroundings to fill in shadows and reduce contrast. Today I am comparing the same modifiers used in a small white space versus used in a small black space. The environment was controlled by building a cave made of foamcore v-flats in the studio. In one “cave” the walls, ceiling, and floor were black. In the other they were white. Too often photographers neglect to take into account the environment they are working in, especially when using studio strobes. We know that the strobes will overpower the ambient light, but the walls, floor, and ceiling will still have an effect on the outcome.

The effect is on the shadow density or the contrast in the image. We know that a larger light source, as seen by the subject, gives a softer light by stretching out the shadow edge transition and filling in the shadows. If the size of the light doesn’t change, the environment has an additional effect on the shadows without affecting the shadow edge transition. This gets confusing. As you will see, the photos made in the white surroundings could be described as softer, even though the shadow transitions are the same. Just as we shouldn’t confuse harshness with brightness, we shouldn’t confuse quality with contrast. We can have a small hard light that is diffused (spread wider) or more focused. We can have a large light that is more focused or spread out more. Diffused doesn’t equal soft. Diffusion spreads the light to cover a wider area. And in doing so it might bounce off of walls to lower contrast. And that might look softer, but in a dark environment we can see that this isn’t true. The size determines the quality (hard/soft) and the diffusion and environment control the contrast.

Let’s look at some of the comparisons.

Same modifier, same distance, totally different look due to the environment. With the white surroundings the light bounces all around and fills in the shadows. The shadow edge, though, is the same quality due to the size being the same.

Same modifier, same distance, totally different look due to the environment. With the white surroundings the light bounces all around and fills in the shadows. The shadow edge, though, is the same quality due to the size being the same.

Here is a 36-inch deep parabolic softbox (16 ribs). Again, a totally different look by changing the environment.

Here is a 36-inch deep parabolic softbox (16 ribs). Again, a totally different look by changing the environment.

Here with a smaller, harder light source, an 11-inch deep metal dish reflector it is easier to see the shadow edge quality remaining the same while the density of the shadows (contrast) changes depending on the environment.

Here with a smaller, harder light source, an 11-inch deep metal dish reflector it is easier to see the shadow edge quality remaining the same while the density of the shadows (contrast) changes depending on the environment.

The same modifier as above (11-inch deep zoom) with a diffusion sock on it. Little difference between the open face and the diffused face in the black surroundings. But when in a white room the shadows open up much more with the diffuser spreading the light to bounce off the walls. But the edge transition range is still the same.

The same modifier as above (11-inch deep zoom) with a diffusion sock on it. Little difference between the open face and the diffused face in the black surroundings. But when in a white room the shadows open up much more with the diffuser spreading the light to bounce off the walls. But the edge transition range is still the same.

With a narrow, controlled light, such as from a snoot, there is less difference between the two environments. The light isn’t allowed to spread out to bounce off the walls, so contrast is similar.

With a narrow, controlled light, such as from a snoot, there is less difference between the two environments. The light isn’t allowed to spread out to bounce off the walls, so contrast is similar.

OK, so much for light vs dark environments. What difference does diffusion make vs. undiffused in the same environment? Let’s take a look at the 60-inch Photek Softlighter with and without its diffusion panel in both environments.

Here in the white cave we see the Softlighter with its diffusion panel on the left and without the diffusion panel on the right.

Here in the white cave we see the Softlighter with its diffusion panel on the left and without the diffusion panel on the right.

And now the same comparison in the black cave.

And now the same comparison in the black cave.

I will leave it up to you to decide how much of an effect the diffusion panel has with the Softlighter. Tell me what you think in the comments below.


Environmental Impact Analysis

Can you tell what modifier was used to make each of these photos?

This is a test, only a test. Below you will find 26 photographs of my favorite mannequin. Your assignment, should you choose to accept it, is to pair up the numbered photos with the lettered modifiers listed below.

In random order the modifiers:


A. Optical spotlight
B. 24-inch square pop-up softbox
C. 1x3 strip box mounted horizontally
D. 11-inch deep zoom reflector with diffusion
E. 40-inch metallic silver umbrella
F. Snoot
G. 60-inch umbrella (Softlighter without diffusion)
H. 7-inch metal dish reflector open face
I. 11-inch deep zoom reflector with 10˚ grid
J. 42-inch white shoot-through umbrella
K. 45-inch Parasail mounted horizontally
L. 60-inch Photek Softlighter
M. 2x3 softbox mounted horizontally
N. 36-inch deep parabolic (16 rod) softbox
O. 11-inch deep zoom with 40˚ grid
P. 2x3 softbox mounted vertically
Q. 36-inch deep parabolic softbox both diffusers
R. 11-inch deep zoom reflector open face
S. 60-inch octabox
T. 45-inch Parasail mounted vertically
U. 36-inch umbrella
V. 46-inch umbrella
W. 1x3 strip box vertical
X. 36-inch deep octa with only inner diffuser
Y. 28-inch folding beauty dish
Z. 22-inch beauty dish

All of the photos were made in a black box so that the environment would not have an effect on the images (no environmental fill bouncing around the subject). Black v-flats on each side, black foamcore on the floor, and a black fabric draped across the top. The only opening was towards the light and camera. The light is in pretty much the same position and distance (4-feet) from the mannequin head. The beauty dishes were in at about 3-feet.

Click on each of the three images below to view a larger version (1097 pixels tall) or click on the links below for an even larger version (2632 pixels tall). White balance is as shot (Daylight) so you can see the color differences between the various modifiers. They vary quite a bit!

Building the light

From the shadows come…

I have been working on a “headshot” project for a large company over the past month or so. I put headshot in quotes because they are using a wider view than a typical headshot. I am actually coming in late on the project. It started with one photographer traveling around the country to do the bulk of the photos (around 600 individuals). After that sprint they are finishing up with local photographers around the country to photograph new hires and do re-takes on some of the originals. That’s where I came into the project to finish up the Seattle office photos. As there were already more than 500 headshots done, I had to match the lighting from the previous photographer.


I was given a rough lighting diagram, seen here, of the five light setup and a few example photos to reference. But I still had to build up the light with the equipment I had available. And here I want to show what went into the build.

There are a few ways to build a lighting setup. Some photographers start with the fill light and build up from there. I like to start with my key light and add the fill and accent lights onto that. So, with that in mind, here we go…

s1 main light

I started with an Interfit Photographic S1 strobe in a Deep Zoom Reflector with a 40-degree grid coming in from camera left. The grid is being used to restrict the light on the subject so it doesn’t hit the background and cause a shadow on the right side of the frame.


The next light is an Interfit Honey Badger in a 7-inch metal dish reflector with a 10-degree grid. This light is placed directly over the lens and is concentrated on the subject’s face. Again, the grid is used to contain the light and not affect the background too much. I had a number of concerns about this light as I was sure that some subjects would be wearing eyeglasses. But with a little bit of angling the direction of their faces, it did not end up being an issue.


The third light in the mix is a 60-inch octa powered by another Honey Badger. This light is directly behind the camera, giving an overall fill and providing a base for the shadows. It doesn’t look like much on its own, but in the overall final image it becomes important.


The fourth light is from another Honey Badger pointed into a 60-inch Photek Softlighter without the diffuser (basically a large umbrella) from camera left to bring out the color of the background and to provide a space for the employee biography that appears with their photograph.


The final light in the setup is another Honey Badger in a 1x3 strip box with a grid. It is set up on a boom arm coming over the top of the roll of seamless paper. It is there to give a tiny bit of separation between the subject’s head and the background.


And finally, all the lights combined for the final image to be delivered. All of the power settings on the lights remained the same from the individuals to them all combined. I found it enlightening to see how they all came together in the final image after looking at how dark most of them were on their own.


Here is what the final setup looked like. The background is Savage Ultramarine seamless paper. About half of the photos were made on this color, and the remaining were photographed on Savage Slate Gray.

The yellow dot on the small extension arm is a tennis ball to make the arm more visible so a klutzy photographer doesn’t walk into it. The client specs called for all persons to be seated on an apple box. The second apple and the foot stool are there to position the feet and legs in different ways to give some variety to the photos.

Indirect light in an Octa

Continuing experimenting with indirect options in large modifiers.

Most softboxes, octaboxes, deep parabolic boxes are used with the light in a “direct” position. That is the light is mounted at the back of the modifier facing forward. This is as opposed to reflective umbrellas where you face the light into the umbrella and have it bounce back at the subject—indirect light. What I have been looking for is a combination where I have a large silver octa or deep parabolic with the light pointing into the modifier instead of directly at the subject. I covered this with the big 7-foot umbrellas in a previous post. Today I am trying this with a 60-inch octa.

To accomplish the reversing of the light I am using a device from Cheetah called a Reflective Focus-able System. This unit is a yoke-mounted speedring for your modifier and a movable rod to hold your light head and allow you to change the distance between the light head and the modifier. Here you can see I have an Interfit Photographic (this is an affiliate link, I will be compensated if you purchase directly from Interfit using my “cornicello10” discount code at checkout) battery powered Badger Unleashed strobe head mounted on the Cheetah device in a 60-inch octa.

By moving the flash head in closer or farther away from the modifier you get control over the pattern of light coming out of the modifier. If you pull the head all the way into the modifier only a small center section of the modifier gets lit and you get strong directional light, almost like a spot light, that will give you hard edged shadows. As you pull the light out farther from the modifier the light fills more of the modifier making it more larger which softens the shadow edges. It is also more diffuse, so it can bounce around the environment and open up the shadows, making them lighter in tonality.

Here are three selfies with the 60-inch octa stationary, but with the flash head adjusted within the octa. At the top the head is pulled all the way into the octa with the flash tube about 9-inches from the surface. You can see a small concentrated catchlight in the eyes and a dark shadow on the side of the nose. In the middle image the octa is still in the same position, but the flash is now about 16-inches from the back of the octa. The catchight has become larger and the shadows a bit softer. In the third image the light is pulled out to 24-inches from the back of the octa and you can see the change in the catchlights, with each panel of the octa becoming its own light, almost like a ring light. The overall light source is larger, so the look is a bit more flat and the background is a bit more open with the light being less directional.

Below is a set of images showing various configurations for the octa, starting with the standard direct mount with inner and outer diffusion panels. Then just the inner diffuser, then no diffuser. Then it gets switched to indirect placement of the flash at various distances from the octa. In all cases the light and the subject are in the same position, only the configuration of the light in the octa has changed. Power levels on the flash were adjusted to maintain the same aperture (f/13) in each of the examples. Click on the image to enlarge.

A big thanks to everyone who stopped me to say “Hi” at WPPI last week. It is always a pleasure to meet people and talk about light. Please check out the updated version of my book “Anatomy of a Studio Portrait” which is now available as either a Kindle Edition or in print.


Good Catch!

Catch light, that is. The life of the portrait.


They say it is all in the eyes. And in portraits the eyes come alive with the presence of a catch light. But before we talk specifically about catch lights, a refresher on reflections. After all, we don’t photograph people, places, or things. We photograph the light that reflects off of those people, places, and things. There are two basic types of reflections. Diffuse reflections define the subject and its texture. We base our exposure on the diffuse reflections, whether that be skin, a tree, a flower, etc. Specular reflections are direct reflections of the light source, like a mirror. We also have shadows, which are areas that don’t get lit.

As you change the distance between your light and your subject the diffuse reflections get brighter or darker. Move them closer together and you have to lower your exposure to maintain the correct exposure. Move them farther apart and you need to provide more exposure. Pretty simple and intuitive. The diffuse reflections loosely follow the Inverse Square Law of physics. I am going to skip the math and science part here, but basically it tells us that changing the distance between the light and the subject will have a bigger effect on the exposure than you might expect. Light falls off rapidly as you move the light farther away.

Then we have the mirror-like specular reflections. Specular reflections are the same brightness as the light source, no matter the distance. You can easily see this by pointing a flashlight (torch) at a mirror and observing the brightness as you move the light closer or farther away. At this point you might start to ask why these highlights don’t follow Inverse Square. The answer is that they do! But in a different way. As you move the light source farther away from your subject the specular reflections get smaller, as you move the light closer the specular reflections get bigger.

Once you have an understanding of this you can start to consciously control the relationship between the various highlights. And that is where we come to discussing the catchlights in the eyes of our subjects. This stems from a question I recently received, “Can I make the catchlights less noticeable by moving the light farther away from my subject?” And the answer is, No. Moving the light farther away will make the catchlights MORE noticeable. They will be smaller, yes, but they will also be brighter in comparison to the diffuse reflections. The followup question was if dimming the light would reduce the brightness of the catchlight. Again, the answer is no. Dimming the light lower both the diffuse and specular reflections and you will need to increase the exposure, leading to the same relationship between them.

Let’s look at what is happening. Start with a light in a softbox at about 36-inches from our subject. We meter the light and find that the proper exposure is at f/8. Now move the light back to 48-inches from the subject. To maintain the same f/8 exposure we have to raise the power of the flash up about 1 stop. Now the face is still at the same exposure level (moving the light back and raising the power level compensated for each other). But the light is 1 stop (2X) brighter and because the catchlight is a mirror reflection, it is now twice as bright than it was before, making it much brighter than the diffuse reflection.

We can also look at this going in the opposite direction, bringing the light in closer to our subject. If we bring our light in 3 times closer, say it was originally at 9 feet away and now we move it in to 3 feet away, what happens? We have to stop down (change aperture or lower the flash power) by 3 stops to maintain the proper exposure. That makes the specular highlights 9 times darker than they were. Let’s see that that looks like in pictures.


In the top image the lights are set 36-inches away from the subject. In the lower image the lights have been moved back to 48-inches from the subject. In doing so I had to increase the flash power by one stop to maintain the correct exposure on the “skin.” This in turn made the catchlights one stop brighter in the lower image. So even though the catchlights are smaller in the lower image, they are brighter in comparison to the rest of the face.

For this next example I attached a small mirror to the mannequin’s forehead and made two photos lit with a 2x3 softbox being reflected directly back to the camera. The one on the left had the light 9 feet away from the subject. The one on the right had the light 3 feet away. You can see how bright the softbox reflection is on the left, causing a lot of lens flare and haze, compared to on the right. The exposure on the face, though remains approximately the same. The reflection in the mirror on the right is 9x less bright by bringing the light in to 1/3 the distance. You can also see the difference in the highlight on the tip of the nose, small and bright when the light is far away, larger and more translucent when the light is in closer. The catchlight in the eyes on the right gives away one of my little signatures, the black bars of tape across the front of the softbox to simulate a multi-plane window.


Let’s look at a different example, this time a still life/product photo. This shiny can was lit with one 60-inch octabank. On the left the light is about 48-inches (120cm) away from the can. On the right the light was moved in to 12-inches (30cm) away. There are a few things to observe here. On the left there is a strong highlight that you can see in the red cap and behind the text on the label. While you can read the label text, it is a bit washed out by the highlight. On the right, with the light in closer, the highlight looks much nicer on the red cap and the text on the label is much easier to read. You might also note that on the right the overall look of the text and the can is lower in contrast and color saturation. That is one of the downsides of using a large soft light in close. A set of soft grids on the octa might have helped bring back the contrast, but at the cost of seeing the grids in the highlights. Below is another series of photographs of this can. This time lit with a 2x3 softbox. On the left the light is 48-inches from the can and we see the bright highlight making the text hard to read. In the middle the softbox is set 12 inches from the can and the text is more readable. Over on the right I added a soft grid to the softbox. I think I see a bit more contrast and saturation, but you can see the cells of the grid in the highlight, especially in the red cap and at the shoulder of the can (see my post about grids for more info).


And now for the controversial question about what shape catchlights are preferred. My preference is for rectangular catchlights. That is the shape you get inside from a window, a doorway, or a skylight. It is also what you get from a wide open sky outdoors. So many people talk about, and advertisements for lighting modifiers mention, “natural” round catchlights. I have to assume they are referring to the shape of the sun. But when we photograph people out in the sun we don’t usually get a round catchlight as they are either squinting, or turning away from the sun. Sure, in many animal photos we see small round dot catchlights, but rarely with people. And they remind me of department store family portraits from the 1960s. It comes down to personal taste. It is a rare client who comments on or requests a specific shape to the catchlights in their eyes. Dare I bring up the topic of pupil size? Maybe next time.

round catch lights

Until then, if you have any questions about this or any other lighting questions please comment below or join my studio lighting group on Facebook.


Light as a Feather

Feathering the light is using the shadow edge of your light to control your shadows.

Most beginning photographers seem to start out in the studio with their light pointed directly at their subject. And this works in many situations. You can keep doing that and all will be well. But if you want to take things up a notch and gain more control over the light on your scene you will need to learn how to position the light to control its coverage. And that’s what we are here for today. Control the stamp of light on your subject be feathering the light.


The first thing to learn about feathering your light is that it does NOT make your light softer. We know that the larger the light source as seen by the subject the softer the light. What happens when you feather the light? Take a look at the images on the right where we are looking over the model’s shoulder at the light. On the top the light is pointing directly at the subject. On the bottom the light has been pivoted towards the camera to point more across the face of the subject. In doing so the light has become narrower, which is smaller. If you think back to the post about shadows you will see this is more like a strip light where the shadow edge quality will be the same up and down (the long dimension of the softbox is still the same size), but the shadows from right to left across the face (the nose shadow) will be harder because the width of the light is narrower.

The light across the face is slightly harder, but it is more even. The coverage is wider. But it isn’t any softer.

We can also feather the light away from the camera, towards the background. This will make the light across the face narrower and harder with deeper shadows. It is more akin to a split light when you do this. Let’s look at examples.

Feathering the light using a hard light source (an 11-inch deep zoom reflector)

Here I am using a hard light source to emphasize the shadow edges. On the left the light is pointed directly at the subject. In the middle the light has been pivoted towards the camera to cover a wider area of the face, opening up some of the shadows while at the same time making the shadow edge harder and more defined. Over on the right side I pivoted the light towards the background for another look that is even more shadowed and contrasty. Again notice that the nose shadow to the side has become very hard edged due to the light becoming much narrower.

Feathering becomes an even more powerful tool when working with multiple subjects in the photo. Here I have two subjects and a hard light.

Again, with the light pointed directly at the pair there is a strong falloff in light from left to right with deep shadows on both faces. By pivoting the light towards the camera the light evens out between the two faces as seen in the middle. Pivoting towards the background makes the difference in exposure between the subjects even farther apart.

Now let’s look at it with a softer light, this time a 2x3-foot softbox.


This time I changed the order and you will see why in a moment. I started out the same with the softbox pointed directly at the subjects. Turning it towards the background exacerbated the problem of uneven exposure on the two subjects. Feathering the light towards the camera for the third image evened out the exposure. And in the bonus image I turned the light even more towards the camera and you can see that this lit up the subject farther from the light more than the subject closer to the light.

Here is a diagram to help explain.

There is your control via feathering.


A Little Help From My Friends?

I have something that I am stumped on. I’ve had a couple of friends tell me they shoot this way and I have seen some “big name” photographers that I have a lot of respect for talk about this. This refers to taking two photos with a slightly longer lens and stitching them together instead of one photo from the same position with a shorter lens.

I am not referring to the “Brenizer Method” of taking a series of photos on location with a long lens and stitching those together to make it look like a wide angle photo with limited depth of field. You can see that in this article from FStoppers. The photos I am referring to are usually made in a studio situation with a plain seamless backdrop.

They talk about the difference in “compression” between the shorter and longer lens. Something about one of these (the longer lens images stitched together) having more impact and intimacy. And this is where I get lost. The “compression” effect comes from the distance between the camera and the subject. All lenses have the same perspective from the same camera position. They just magnify more (longer lens) or magnify less (the shorter lens). If you take the image with each lens without moving the camera and crop them the same the scene will look the same. The perspective is the same in the area of the images that are common to each other. The only difference I can imagine is that when you pan the longer lens side to side for the two photos the camera is at a slightly different angle, but not enough to be all that noticeable.

The top image was made at 70mm with the camera horizontal. The lower images were made at 106mm with the camera vertical.

The top image was made at 70mm with the camera horizontal. The lower images were made at 106mm with the camera vertical.

I’ve tried it myself and don’t see any super noticeable differences between the images to make the process of photographing the scene (usually a portrait) twice and then aligning layers in Photoshop. Here are some images where I tried this.

My camera was firmly locked down on a tripod and I made the first image at 70mm with the camera horizontal. Then, without changing the distance I changed the focal length to 106mm and rotated the camera on axis to vertical and took the next two photos, panning the camera a little bit left and right to capture the width of the single 70mm capture.

I then brought the images into Photoshop. There I had the two 106mm images in one document on two layers. I used Auto Align Layers to merge them together into one wider image, then flattened the image.

Next I brought the 70mm image into the same Photoshop document on its own layer and again used Auto-align layers to size them the same. And here are the two results…

Single capture at 70mm

Single capture at 70mm

Two captures at 106mm stitched to create one composite image.

Two captures at 106mm stitched to create one composite image.

Here are the two photos in a slider. On the left is the photo made with the shorter lens. On the right is the photo created by stitching together the two image from the longer lens. The only difference I see is at the bottom of the image and I think that has something to do with the centering of the lens and the act of rotating the camera from horizontal to vertical. I see no difference in the face of the subject.


Those of you who use this technique, what am I leaving out or doing wrong? Can you send me a set of images where one was made with the shorter lens and the other is made from longer lens images stitched together where you can clearly see the difference?



What are all those numbers?

“The tremendous number of speedlights in all shapes, sizes and prices exhibited at recent photo shows leaves even the electronic flash engineer confused. With all the claims, counter-claims and partial information. It is no wonder that the dealer is wary. On top of that, think of the poor customer. Confronted with the array of claims, and with no basis for comparison, it is amazing that so many have the courage to buy. What is more sorely needed are a few simple facts that can be used asa a basis of comparison. “

Though it sounds current, the above is a quote from an article by Harry L. Parker, president of the American Speedlight Corp. (ASCOR) in Photographic Trade News, May 1953. And it holds true today.

Let’s look at just one term, watt-seconds. What does that refer to? Is it related to watts that we commonly use to talk about continuous light? Does it tell us how much light a flash unit produces? Here are some quotes from publications by ASCOR, Norman, and Paul C. Bufff:

ASCOR (1950s): “MASS CONFUSION — For too long most people have rated speedlights (not the same thing as what we refer to as speed lights today, these were units that weighed hundreds of pounds and stored thousands of watt-seconds of energy in their capacitors: ED) in watt-seconds. Just what is a watt-second? If you really know, you are one of the unusual photographers. Then again, what photographer really cares? Watt-seconds is not a rating of light output or speedlight equipment. The use of watt-seconds, microfarads, and other terms has so confused the photographer that many are thoroughly baffled about electronic flash.”

Norman (1970s): “HOW MUCH LIGHT — For many years the common term used to describe the output of an electronic flash unit has been watt seconds. Unfortunately this is very misleading in that the term ‘watt seconds’ is used to describe the amount of energy store in the main discharge capacitors and is not directly related to the amount of actual light output.” (You can download a set of Norman flash guide pamphlets here.)

Paul C. Buff (1990s): Wattseconds defines the amount of electrical power supplied to the flashtube(s); not the light energy which the tubes emit. There are several design factors that affect how efficiently the flashtube converts electrical energy into useable light. These same factors also affect the flash duration. The same parameters which tend to decrease system efficiency also work to shorten flash duration, potentially to the point of inviting reciprocity-induced color errors…” (More on the Paul Buff site.) This was obviously written in the film days, whereas with digital we don’t have to worry about reciprocity departure and people are clamoring for short flash durations so they can splash milk on their subjects.

So, how do you compare the output from one flash/strobe to another? You pretty much cannot do it from the specs. You need to have both flashes in hand with the same modifier on each and do your own A/B comparisons. Luckily with digital we aren’t as beholden to super powerful flashes like we were in the film days working with 8x10 cameras at f/64 with a bellows factor added in requiring multiple pops from a 2400 ws box for a still life setup. For portrait photographers 200 ws would be my starting suggestion, and around 500 ws at the top end—and make sure that the strobe has the ability to dial down. I find more situations where I want less power from my strobes than more.

And everyone makes it difficult to tell just how much power you are using. There is a very popular line of flashes that use more speed light-like power descriptions: full, 1/2, 1/4, 1/8, 1/16, etc. This would be all well and good if all of their flashes had the same power. But what happens if you want to compare different models of their flashes on the same set? Flash A is 600ws, so 1/4 power is 150ws. Flash B is 320ws, to 1/4 power on that unit is only 80ws. Very frustrating if someone is trying to describe their lighting to you and says one light was at 1/32 power and the other was at 1/8 power. If the two lights aren’t the same, they could be putting out the same power as each other. Or the 1/8 power flash could be brighter than the 1/32 power flash. You have no way of knowing unless you know exactly which model(s) of flash units that person is using in which position.

Theoretically the number system of power levels should help compare output. As I understand it, when originally proposed it was to be based on a particular reflector and distance that could be replicated between brands. Say, for example a company had flashes ranging from 900ws to 3600ws with the same reflector and distance 10 would be the highest level (3600ws). Their 1800ws unit would only go to power level 9 (1 stop less), and there 900ws unit would top out at power level 8. Then another manufacturer would test their lights with a similar modifier/reflector at the same distance and even if the WS rating was different, say 600ws, if it put out the same amount of light as the original’s 900ws unit its top setting would be 8. Then you would know that any light that went to power level 10 had the same output. Any light set to 9.3 would be the same, etc., etc. However, in practice this has not caught on. Most flashes seem to just use 10 as their top level, no matter the actual output.

Oh, well… Pick a brand of lights (my choice is Interfit*) and enjoy them. Don’t compare them to others. Make the best photos you can. Light is light. Put your energy into the creative side.

*Yes, this is an affiliate link. If you purchase via this link or use the code “cornicello10” at checkout from Interfit you will get a 10% discount on your order (and free shipping on orders over $100) and I will get credit and may be compensated for directing you to them.