Breaking the law

Can grids help you break the law?

If you are using soft grids on a softbox in very close to your subject you might be breaking the law. The Inverse Square Law, that is.

inverse-square.jpg

Just about everyone learning how to work with light learns about the Inverse Square Law early on. “The intensity of light falling on a flat surface at right angles to a point source of light is inversely proportional to the square of the distance.” If you double the distance between the light and the subject you get 1/4 the amount of light on the subject. Triple the distance and you get 1/9 the light on the subject.

In practice it isn’t so cut and dried. The law applies to a point source of light—we rarely encounter that in our photography. Simplifying it down, it says that as you increase the distance between a light source and a subject the light spreads out and appears to fall off in intensity very quickly. There isn’t less light, but the light is covering a wider area, so fewer photons are reaching the subject with the balance of them zooming on by past the subject and not contributing to the illumination.

Here you can see me using a light meter to measure the output from a 2x3-foot softbox in close and a bit farther away. Without the grid the light falls off as expected, going from f/6.3 in close to f/5.0 backed away. But when the grid is in place the meter reads the same f/5.0 at both distances. Have I broken the law.

metering-1.jpg
metering-2.jpg

What is going on is that in close the meter sees a small number of very bright grid cells. As you back up a bit, but still in close, the meter sees a greater number of cells, but they are less bright. And this averages out to give the same exposure reading at the different distances. This just happens in close. Once you back away to a point where the meter can see the entire softbox things go back to normal and light falls off as expected.

Let’s take a step back to look at what grids do. Grids are the opposite of diffusion. Grids are baffles that control the spread of light. They increase contrast by blocking the light from hitting walls, floors, ceilings, or anything else in the environment that would become a secondary light source reflecting light into the scene to open up the shadows. They also help control the spill of light onto the backdrop.

So, how does this affect photographs? Normally, without the soft grid, as you move your light in closer to your subject the light gets larger as seen by the subject. We say it gets very soft because it fills in its own shadows and causes the shadow edge transition to spread out. It also leads to a loss in color saturation. With the grid, as you move the light closer to the subject the grid cells occludes light from the edges of the softbox so once the light gets close enough for that to happen it appears smaller as seen by the subject. Then as you move it in even closer its size appears to stay the same and the contrast and saturation remain the same.

You can use the slider on the right to compare the scene with and without the grid to see the change in contrast along with the slight change in color saturation. Both images are lit with a 2x3 softbox positioned 12 inches away from the tip of the mannequin’s nose and both were metered at f/9.0. Although at the same distance, the scene lit with the grids has a harder light quality because the grids made the light appear to be smaller. If the softbox was moved back to a distance where the subject sees the entire box the differences go away.

The grid on the softbox is seen in the catchlight in the eye.

The grid on the softbox is seen in the catchlight in the eye.

The downside of soft grids is that they show up in reflections. That could be in the catchlight in the eyes of a portrait subject, as you can see here, or in shiny objects in a still life photograph.

Don’t be tempted to put some diffusion over the grid, though, to try to hide the pattern. The diffusion will completely counteract the effect of the grid.

Thanks again for following along! Send me your studio lighting questions. Or take a look at my updated book, Anatomy of a Studio Portrait.

Cheers!
John

What does that modifier look like?

I had a few spare minutes yesterday (New Year’s Eve), so invited a friend and her daughter over to make some photographs with a variety of light modifiers. Here are the results of the 28 configurations we tested.

All photos lit with an Interfit Photographic Honey Badger strobe head. All photos metered to f/6.3. Subject seated about 2 feet in front of white seamless paper. All lit with the single light with no reflectors or fill light. Camera was set to “daylight” white balance (yes there is that big a difference in skin tone between them) and the only post-processing on the images was to crop them to a square.

Here is the list of modifiers used and some notes:

  • Interfit 48-inch deep parabolic softbox with both diffusers in place

  • Interfit 48-inch deep parabolic softbox with only the inner diffuser

  • Interfit 48-inch deep parabolic softbox with no diffusers (open face)

  • Interfit 48-inch deep parabolic softbox with 20-inch black foam-core disk blocking the middle of the light (looks like a ring light)*

  • Neewer 36-inch parabolic softbox with CheetahStand focusing rod with the flash head pulled all the way in to the softbox

  • Neewer 36-inch parabolic softbox with CheetahStand focusing rod with the flash extended to the opening of the softbox

  • Neewer 36-inch parabolic softbox with CheetahStand focusing rod with the flash extended to the opening of the softbox and a 20-inch black foamcore disk blocking out the middle of the light*

  • SPSystems 28-inch folding octabox with both diffusers in place Light boomed over camera on axis with lens

  • SPSystems 28-inch folding octabox with only the inner diffuser

  • 22-inch Speedotron beauty dish centered over the camera with diffusion sock

  • 22-inch Speedotron beauty dish without the sock

  • 20-inch metal dish reflector centered over the camera

  • 20-inch metal dish reflector with a diffusion sock on it

  • Interfit Deep Zoom reflector at camera left

  • Interfit Deep Zoom reflector with its diffusion sock

  • Interfit Deep Zoom reflector with 10-degree grid

  • Interfit Deep Zoom reflector with 10-degree grid and diffuser to show that the diffuser negates the effect of the grid

  • 7-inch metal dish reflector

  • 7-inch metal dish reflector with one sheet of #261 diffusion

  • 7-inch metal dish reflector with two sheets of #261 diffusion

  • 7-inch metal dish reflector with 10-degree grid

  • Interfit 2x3-foot softbox pointed directly at the subjects

  • Interfit 2x3-foot softbox feathered in front of the subjects

  • Interfit 2x2-foot collapsible softbox (which comes with the Honey Badger and has a recessed front panel)

  • 2x2 softbox with a flat front (old and apparently yellowed with age)

  • Interfit 65-inch** Silver Parabolic umbrella with the head pushed almost all the way into the umbrella

  • Interfit 65-inch** Silver Parabolic umbrella with the head pushed in (focused) and a 20-inch black foam-core disk blocking the center of the light

  • Interfit 65-inch** Silver Parabolic umbrella with the head mounted on a separate light stand about 5-feet in front of the umbrella

    * see the photo below
    **measured across the opening, other companies call this a 7-foot or an 84-inch as they measure around the back arc of the umbrella

The black foam-core disk was used in an attempt to make the lights act something like a defocused Broncolor Para. The sliding focusing arm in the 36-inch para was for the same reason. But looking at the photos, I think that I like the big 48-inch Interfit Parabolic Softbox in any of its configurations (2 diffusers, inner diffuser, no diffuser).

Some photos for clarification

Strobe head mounted on a separate stand 5 feet in front of the Interfit 65-inch Silver Parabolic Umbrella

Strobe head mounted on a separate stand 5 feet in front of the Interfit 65-inch Silver Parabolic Umbrella

Black foam-core disk blocking the center of the deep parabolic softbox

Black foam-core disk blocking the center of the deep parabolic softbox

Cheetah “Chopstick” lets you position the flash head inside the softbox, sliding it closer to or farther from the back of the softbox to focus the light

Cheetah “Chopstick” lets you position the flash head inside the softbox, sliding it closer to or farther from the back of the softbox to focus the light

What information lurks in the shadows?

Only the Shadow knows.

And he has something to say! Shadows are a very important piece of our photographs. Shadows help define our subject. They help set the mood of the photograph. They can hide things we don’t want to show. They can tell a story about how a scene was lit. And that’s what I am talking about today. What can we see in the shadows?

Here are my descriptions for the 14 images on the right (click on the image for a larger version):

  1. Standard 7-inch metal dish reflector
    Notice slight double-edge to the shadow due to the flash tube being slightly brighter than the surrounding reflector.

  2. Standard 7-inch metal dish reflector with one layer of diffusion material
    Contrast is lower from light bouncing around the room, shadow edge is more homogenized by the diffuser. The shadow edge is the same, no extra softening from the diffusion, just a brighter shadow.

  3. Standard 7-inch metal dish reflector with two layers of diffusion material
    Very similar to #2 but needing more flash power. Extra diffusion did warm up the color. Still has the same edge with no additional softening.

  4. Standard 7-inch metal dish reflector with 10-degree grid
    Narrow beam of light doesn’t hit walls, ceilings, etc. (environment), so more contrast. Still has the same shadow edge quality, just a darker shadow and restricted coverage on the background.

  5. Standard 7-inch metal dish reflector with 10-degree grid plus a layer of diffusion
    Brings us back to what we had in #1 or #2, but required 5 more stops of light power to maintain the same exposure. Don’t put diffusion in front of a grid! It negates the effect of the grid at the cost of a lot of your flash power.

  6. Deep Zoom 11-inch reflector
    Narrower light been from the deep reflector gives a darker shadow, somewhat similar to the grid in #4, but like #1 the shadow edge is doubled because of the difference in efficiency between the light direct from the flash tube and the light bounced off the walls of the reflector. Diffusion would help homogenize the shadow, but will also take away some of the contrast.

  7. Deep Zoom 11-inch reflector with 10-degree grid
    Even less environmental bounce producing a darker shadow.

  8. 1x3 strip box in vertical position
    Narrow modifier produces little shadow along its long dimension (up/down here) with much more shadow along its shorter dimension (left/right here).

  9. 1x3 strip box in horizontal position
    Rotating the narrow box moves the shadows. The left/right shadows are a little bit tighter while we now have up/down shadows. This is especially noticeable on the light stand holding the silhouette. In #8 it casts a wide shadow, while in #9 the wide pattern wraps around the narrow object and there is virtually no shadow.

  10. 2x2-foot square softbox in close at 3-feet
    This softbox has both an inner and outer diffusion panel. Shadow transition is soft

  11. 2x2-foot square softbox backed up to 6 feet
    The box gets smaller in relation to the subject when moved back.The shadow gets a harder and more defined edge. The background brightens up slightly (depth of light, inverse square law). More light bounces around the room picking up some warmth from the wooden floor.

  12. 2x2-foot square softbox at 6 feet with an extra layer of diffusion
    Shadow quality remains the same, but image picked up some warmth from either the wood floor bouncing in or from the diffusion material (or both). Requires more flash power.

  13. 46-inch Photek Softlighter umbrella WITHOUT the diffuser
    Large, round light. Even shadows all around. Background is brighter than #14 due to longer light path and depth. Although the umbrella is 36 inches from the subject, the light path is from the flash to the umbrella (24-inches) and from the umbrella to the wall (36-inches) so the distance of light is like having a forward facing light at 5-feet away instead of 3-feet, as you would get with the front diffuser (see #14).

  14. 46-inch Photek Softlighter umbrella with the diffuser
    Adding the diffusion cover has a slight effect on lightening the shadow density. Background is slightly darker as the light source (the diffusion panel) is closer to the subject. The closer the light is to your subject, the darker the background will be.

All the photos were metered to give the same exposure. In most cases the aperture remained the same (f/4.0) and the flash power was adjusted to maintain correct exposure. The exceptions are the exxamples with the Deep Zoom reflector, as it was very efficient and I could not lower the flash power enough so I had to stop down the lens to f/7.1. 

The main take-aways from this lesson is that the shape of your modifier determines the shape of the shadows and the size of the light as seen by the subject determines the size of the shadow width or the quality of light, that is hard or soft. Diffusion, along with the environment, controls the shadow density or contrast. Adding diffusion directly to a light, where it doesn’t make the light any larger, does not soften the light. It is a very subtle, but important concept. Diffusion does homogenize the light, making it more even across its field. And, depending on the environment, fills in the shadows making them less dark by bouncing off the walls, floor, ceiling, and other surroundings. Don’t confuse contrast with quality.

As I said, the difference can be subtle. Here we have three photos to compare. The first (A) was lit with a standard 7-inch diameter silver metal dish reflector. It casts a hard edged deep shadow. Next, I taped a sheet of diffusion material over the reflector (B) and you can see that the edge shape and transition (quality) has remained the same. What changed was the depth or darkness of the shadow (contrast). The diffusion spread the light around the studio and made the shadows lighter in tone, but the edge didn’t change because the light size didn’t change. For the third photo (C) I switched to a 20-inch diameter light modifier without diffusion and you can see here that the edge got softer and the transition got wider as the light was able to “wrap” around the subject for a softer light quality.

contrast-vs-quality.jpg

Now let’s look at what happens when we keep the same small 7-inch diameter reflector but add single and double diffusion. The first sheet of diffusion material makes the shadow brighter and also homogenizes the shadow edge so there is no longer a double-shadow (from the flash tube and the reflector not being equal in brightness). Adding the second layer of diffusion slightly lightens the shadow, but not appreciably. It does not in any way soften the light.

multi-diffusion.jpg
triple-diffusion

I can anticipate a comment and question. That’s all well and good for diffusing a small light. I am using a Photek Softlighter and want to double (or triple) the diffusion on that. What happens there? Let’s take a look! Here are four examples starting with the Softlighter umbrella on its own without the diffuser. Next is with the diffuser. Then for double diffusion I hung a roll of diffusion material in front of the Softlighter to double-diffuse it. Then I doubled that up to make it triple-diffused (see the photo on the right). Adding the diffusion panel to the bare umbrella actually limits the spread of the light and makes the shadow a bit darker. Adding additional layers of diffusion on top of that brighten the shadows ever so slightly and start to add some warmth to the color. But again, no change in the quality/softness of the light from extra diffusion. The size of the light remained the same.

This environmental bounce can also cause color casts if the room isn’t neutral in color. In a larger studio, or in a studio with black walls, ceiling, and floors, or in an open field the changes in contrast on the subject with or without diffusion and grids will be much less noticeable.

 

 

Well, this brings us to the close of another year. 2018 has been quite a year for me. The biggest event was the passing of my 98-year-old mom, Rose, in August. Thanks for everything you have done for me and for all the support for my taking my own direction in life. I could not have had a better mom. Rest in peace.

So, here is looking to a bright new year with new challenges and accomplishments. I wish you all a Happy New Year! Stay safe and be well.

Cheers!
John














When your big light just ain't so big

Lighting a group

We all know that a large light in close to the subject is a soft light. As we move the light back away from the subject a couple of things happen. First, the light gets deeper. Second, the light gets smaller.

Deeper
When you move your light back the light rays are more parallel and fall-off in intensity slower. At one extreme we have sunlight. The sun is so far away that light rays reaching the earth are almost parallel. The same amount of light reaches you where you are standing as reaches someone else a block or two away from you (or miles away). So we know that if we have to light a group of people with a number of rows we need to move the light back so a similar amount of light reaches the back row as reaches the front row. If the light(s) is too close in the fall off will be rapid and the back row will be dark or the front row will be overexposed.

Smaller
Smaller light equals more defined shadows. A small light cannot “wrap” around the subject to cause a wide shadow edge.

Diminishing Returns

(click to enlarge)

I feel that after a certain distance the size of the light doesn't really matter all that much. A 60-inch umbrella far away is just as hard as a smaller modifier. So, I gathered up the studio staff for a group photo and lit it three ways.

Have you met the staff? An interesting bunch. Over on the left we have our lobotomy patient, next is our exhibitionist, then the lowly photographer, and finally that guy who is just a shadow of his former self. Look for a new post about shadows coming soon to this blog.

The light was set up 9-feet away from the group and flash power was adjusted to give f/7.1 in each photo. The first photo is with the 60-inch umbrella. The second photo is with the 7-inch dish. The third photo is the same 7-inch, but with a sheet of diffusion material taped to the front of the reflector.
Looking at the three photos, the big difference between them is in the shadow density. As I expected, the 60-inch has the lightest tone shadows, followed by the diffused reflector. They each allowed more light to bounce around the room to open up the shadows.
But what about the light on the faces? Surely the big umbrella is going to be the clear winner here. Or is it? I see very little difference in the light on the faces in these three photos. It just took a lot more flash power to light with the umbrella than with the smaller, more efficient reflector. And that can be a big consideration if you are going out on location to make the group photo, especially if using battery-powered flashes. However, the umbrella or the dish with diffuser will cast a wider area of light that you might need for a very large group if you want to stay with a single light source.
Of course, if this was to be a portrait of one or two people, I could have the big light in much closer and could be more creative with lighting patterns, and separating the subject from the background, and on and on, etc., etc. But for groups you need to pull the lights back. And, in doing so, you might find that you don't need as large a light or as much strobe power as you thought you would.

 

 

BONUS MATERIAL

Many aspects of photography are related and many of them deal with distances. Here are some ways you can apply knowledge about one aspect of photography to learning another. First we have depth of field and depth of light. As you move your camera back away from your subject your depth of field (the area of the scene that appears reasonably sharp) gets larger. Taking that to lighting, as you move your light back away from your subject your depth of light gets larger. The closer the light is to your subject, the darker the background will be. The closer your camera/lens/aperture combination is to your subject, the more shallow the depth of field.

Next is perspective. The closer your camera is to your subject, the smaller the background will appear. Conversely, as you move back away from your subject the background gets larger. This is often mis-labled as telephoto compression, but it is the physical act of moving back that causes the change. You just tend to use a longer lens when farther back to magnify the subject to fill the frame, which makes people blame the lens.

Very much related to this is how a face looks in a photograph. The closer your camera is to your subject the more pronounced their features will appear. As you move back away from your subject their features flatten out. In close your subject’s nose looks bigger in relation to their eyes and ears. But as you move back the features flatten out as the nose, eyes, and ears get relatively closer to each other than to the camera. When you move back you can switch to a longer focal length lens again to fill the frame, but like before it is the physical moving back that changes the depth of features of the face. As in the lighting situation above, there is a point of diminishing return. Once you are in the range of 12-15 feet away from your subject I don’t think that moving any farther back will have any more effect.

How do you like to light large groups of people?

How do you apply what you know about one aspect of photography to other aspects?

Thanks again for following along!
John


Light as a feather

What does it mean to “feather” your light?

The first thing many people will say is that it makes the light softer. But is that really true? Let’s take a look. To feather the light means that you turn the light so it isn’t pointing directly at your subject. As we should all know, the softness of the light comes from the size of the light in relation to the subject. A big light in close gives a soft light with its size allowing light to reach the subject from multiple angles and filling in its own shadows. That same light backed up farther away becomes smaller as seen by the subject. Light comes in from more restricted angles and the shadow edge quality gets harder.

What happens when you take a softbox and rotate it away from your subject? The height of the box remains the same, but the width gets narrower (smaller) as you turn it away, making it look more like a strip light to the subject. As the height remains the same the up/down shadows (under the chin, under the nose, under the eye sockets) will remain the same. But side-to-side shadows (the side of the nose) will get slightly harder. If you don’t make the light source larger, it will not get any softer.

OK, if feathering doesn’t soften the light, what does it do?

Feathering gives you control. You get to place the edge of the light from your softbox and you get to control the balance the intensity of light on the cheeks of your subject. Let’s take a look.

For this series of images I used a flash meter at the point marked in the upper left image to measure an exposure of f/4 (ISO 100, 1/125 sec.) and I varied the flash power between each image to maintain the same f/4.0 reading on all five images. The inset diagrams show the lighting setups from above and the second row of photos shows the setup from the side. There were no fill cards or fill lights used. All images are straight out of camera with no exposure or color adjustments. The light, an Interfit Photographic Honey Badger was modified with the 24x24 popup softbox that comes with the light. Both the inner and outer diffusers were in place and it was 18-inches from the nose of the mannequin in the middle image. (FCC Warning: that is an affiliate link, I may be compensated if you purchase something there using code “cornicello10” at checkout—and you get 10% off!)

Pay close attention to the nose shadows in the photos above. They stay pretty much the same throughout the series. What changes is the exposure balance between the two sides of the face. Pointed behind the subject the cheek closest to the light is much brighter than the other cheek. As the light is turned towards and then beyond the subject the highlight moves across the face. At first the two cheeks come closer to each other in brightness. Then finally with the light pointing away from the subject and towards the camera the other cheek gets slightly brighter than the cheek on the side with the light. The power on the light had to be brought up quite a bit on the last image because it was pointing quite a bit forward, lighting up more of the environment in front of the subject, causing a bit of a change in color, too. My last blog post was about environmental bounce. Check it out if you get a chance.

Distance matters, too. As you move your light back farther from your subject the light pattern grows and transition area gets larger. This can help when photographing groups of people with a single light. By backing the light up and pointing the light across the front of the group you can get even coverage across the group. Here is a group photo of the staff of PCNW in Seattle. It is lit by one large umbrella slightly to the side and slightly feathered across the group.

Click on the image to enlarge it

To answer some questions that might come up…


What is the difference between using a softbox with a recessed front panel versus one with a flush front panel? The recessed panel with its miniature barn doors gives more control over where you place the edge of the light and has quicker fall-off with darker shadows. Here is a set of comparison images lit with the same size softboxes with and without a recessed front diffuser. For the third row I added a white foam-core bounce board as a fill light.

beauty-direct.jpg

Yes, you can feather up and down to control the balance of light from the forehead down to the chin. It is not uncommon to have your light look like it is pointing at the ground in front of your subject or pointing up into the air above your subject to get the desired pool of light on your subject’s face so that the forehead is not too bright compared to the nose and chin. Your light might end up looking like it is not pointing at your subject at all. The important thing is what the light looks like on your subject, not what the actual light looks like.

Yes, you can feather an umbrella or a hard reflector or a beauty dish. WIth an umbrella or beauty dish be careful to not turn the light so far that the bare flash can be seen by the subject, hitting them with harsh direct light from a small light source (the flash tube).

What are your questions about feathering light?

Parabolic Umbrellas

Getting the most from your parabolic umbrella

It has been a few years now since Paul Buff (Alien Bees) introduced their 86-inch PLM (Parabolic Light Modifier) umbrella, which was quickly followed up by similar umbrellas from other companies. Some call them a 7-foot umbrella (measured across the arc of the back of the umbrella), some call then 65-inch umbrellas (measured across the opening of the umbrella). They come in a variety of styles—white reflective, dull silver, shiny silver, and translucent (shoot through). They have 16 ribs/panels (most photo umbrellas have 8, while the Photek GoodLighter and Softlighter have 10). The more ribs, the closer the shape comes to being round.

But it is not just about the shape (mostly noticed in the catchlights of people). Before all of these inexpensive parabolic umbrellas there were others at much greater price from companies like Broncolor and Briese. I believe it was all started by Briese, but their market is mostly in the film industry. More photographers around the world are familiar with the Broncolor Para modifiers that come in a variety sizes from their Para 88 (about 3-feet across the front) to the Para 330 (almost 11-feet across the front opening). Prices range from $3,000 to $7,000 or more just for the umbrella system.

These original parabolic reflectors provide a wide range of looks by having a mechanism to move the lamp head within the umbrella to focus or defocus the light. With the lamp placed deep into the umbrella you can find the focus spot that turns it into a gigantic spotlight that collimates the light rays emerging from it. But many people feel that the real beauty from the para comes when it is defocused. To do that bring the lamp head all the way out to the edge of the umbrella. With its 24 shiny silver panels the center of the umbrella goes dark and you wind up with 24 small bright spotlights around the edge, making it into a gigantic ring light.

It is this soft, yet hard, ring light quality that I have found to be lacking in the 7-foot class parabolic umbrellas. For most of the time that I have owned these big umbrellas I have basically used them as umbrellas for fill light or with a heavy diffusion fabric across the front turning them into big round softboxes. That is fine for the white reflective and the translucent umbrellas. But that silver umbrella. There had to be more to it.

For the photos in this article I will be using the shiny silver version of the Interfit Photographic 65-inch Parabolic Umbrella with their Honey Badger studio flash. You can slide your lamp all the way in on the shaft of these umbrellas to create a strong spotlight like effect. But drawing the head out to the end of the shaft doesn’t get to the ring light look. Take a look at the first two photos of the silver umbrella with the head all the way in making for a concentrated light and then with the head pulled out to the very end of the shaft. The center is still the hot spot in the umbrella. Where are those spotlights around the edge of the umbrella?

Flash head mounted far down the shaft of the umbrella

Flash head mounted far down the shaft of the umbrella

Flash head mounted as far out on the umbrella shaft as possible

Flash head mounted as far out on the umbrella shaft as possible

Flash head mounted on a separate stand 5-feet out from the umbrella

Flash head mounted on a separate stand 5-feet out from the umbrella

para-compare.jpg

For a while I’ve been thinking about ways to make these umbrellas act a bit more like the Para. I don’t expect to match it exactly, but I was sure that I could do better than what I’ve been getting. It finally dawned on me to take the lamp head off of the umbrella shaft and mount it on a separate light stand so I could pull it even further out of the umbrella. Take a look at the light pattern in the umbrella in the third photo where I have placed the lamp 5-feet (60-inches) from the center of the umbrella instead of at the 31-inches when mounted on the umbrella shaft. This is starting to look more like what I’ve been trying to achieve. The edge lights are not quite as small as I would like, but I think that comes from the overall shape of the umbrella. The true paras are deeper and more of a cone shape than the 7-footers.

What does all that translate to on the other side of the camera? Here are three self portraits made with the lamp head in the three positions. The modifier and camera remained stationary between these photos with the umbrella about 8-feet away from the subject and white seamless paper about 2-feet behind the subject.

Flash head mounted far up the umbrella shaft

Flash head mounted far up the umbrella shaft

Flash head pulled back to the end of the umbrella shaft

Flash head pulled back to the end of the umbrella shaft

Flash head mounted outside the umbrella

Flash head mounted outside the umbrella

head-outside4.jpg

The first image feels a bit harsh and contrasty for my taste. The second is a little nicer with a bit more of a feeling of the light wrapping. Third image is my choice for contrast and quality. Notice the color change in the third photo. In the first two images the light is pretty well contained within the modifier and doesn’t bounce all around the room (what I call environmental bounce). In the third image the flash head is well outside the modifier, as shown on the right, bouncing light around the room which has a golden colored wood floor, which becomes a secondary light source, which warms up the image considerably.

Here are closeups of the catchlights in each of the above. Some might find the ring light look in the third image distracting. Other people might not ever notice it.

With the lamp head way out in front of the modifier you need to be careful about the light striking the front of the lens causing flare. The lens hood might not be enough. You might need to set up a flag between the light and the lens depending on how close you are trying to get the light to your subject.

You can stop reading here if you like. But if you want to geek out a bit about parabolas, I’ve added the following section.

Going more into the geek…

Let’s look at what makes a parabola. First the standard definition: a symmetrical open plane curve formed by the intersection of a cone with a plane parallel to its side. 

WHAT???

parabola-focused.jpg
parabola-defocused.jpg

Basically, it is a U-shaped curve. You can read tons more on Wikipedia. Here we are concerned less with what a parabola is or how it is formed, but more about what it does to light. Within the parabola is a focus point on the axis of symmetry and outside is a line called the directix. The parabola is the shape defined when all the points on a line are equidistant from both the focus point and the directix. Visually, it goes something like this on the right.

When talking about light, a (theoretical) point source placed at the focus point is reflected into a parallel beam, leaving the parabola in parallel rays. In actual practice let’s just say that the light is deep (falls off slower than inverse square would predict) and contained or directional. Various factors prevent the light rays from being truly parallel. There is little environmental bounce, so the light is contrasty, but it is also large, so it fills in some shadows. You will need to experiment with having the light at different distances from the subject to find the look that you like.

If the lamp is moved further out of the parabola—defocused—the light rays are scattered (diffused) and exit in a diverging pattern, but the center goes dark and you get a ring of bright spotlight-like lights around the edge of the reflector. The overall exposure will be less as more of the light is spread out and bypassing the subject. Again, experiment with different light-to-subject distances, erring towards having the light closer in the smaller the parabolic umbrella you are using.