Gonna just type a bunch of thoughts here. (edit, looks like I typed a lot)
Your first step should be to determine what type of portrait you want to make. A standard boring business-style headshot, a glam beauty portrait, a gritty or moody look, a dark and scary look. Different subjects have different needs. I like dark and gritty and high-contrast and scary, but I sure wouldn't use that sort of lighting when making a headshot for a dentist to put on his business cards.
Second step is to analyze others' work that you like, really study it, challenge yourself to try to determine their lighting setup. Do this on every photo you see. Some things to analyze:
Position and hardness of the shadow cast by the nose and chin
Catchlight(s) in the eyes
Rim/edge light on the shoulders, or a glow from a hair light
Definition of skin texture
When lighting a portrait, consider all the following factors for every light you're using - flashes, ambient, interior room lighting, sunshine, etc.
- Positioning of each light in relation to the subject (and background)
- Direction of each light in relation to the subject (and background)
- Size of each modifier (relative to the size of the subject)
- Power level of each light
- Distance from each light source to subject
- Color of each light source
Most portraits start off with one light being the primary light source - this is your main or key light. This is often the brightest light in the setup, but not always. This is sometimes the largest modifier in the setup, but not always. You can put this light in a variety of positions, refer to the first link provided by Alveric above.
-- Main light important note #1: For most portraits, it's very important that the main light is higher than the subject's nose, or higher than their head altogether. When the main light is below nose level, it looks unnatural and weird and creepy and usually unflattering.
-- Main light important note #2: The change from butterfly lighting to loop lighting is very simple. You can move the main light, OR you can just have the subject move their head. It doesn't matter where the main light is, if the subject points their nose right under the bottom edge of the main light, you're getting butterfly lighting. if they point their nose a little off to the side, you get loop lighting. Moving the subject's nose is WAY EASIER than moving the light stand.
Most portraits (but not all) will include a second or third light source. These can act in a variety of ways, depending on the style of portrait you want to make.
For standard portraits, you want a fill light. Its purpose is to lift and soften the shadows cast by the main light. For business headshots and glam/beauty portraits, you usually don't want hard, dark shadows cast by the facial features. You want just a hint of shadow, just enough to give definition and shape to the face. In this case, your fill light will be almost (not quite) as powerful as the main light, and positioned near the camera, and relatively large, so everything that the camera sees is lit by the main light or filled by the fill light.
For separation from the background - and this is going to be very important with your black backdrop in your setup - it's very useful to have a rim light, kicker light, hair light. This one is placed behind/above the subject, pointing at the top of the subject's shoulders or head. This will give a little edge or rim, to define the shape of the subject and make them pop off the background. If you have a black background, a main and fill light, and a subject with black hair and a dark suit, without a rim or kicker light, they're going to sink into the background.
OR. Instead of a rim/kicker light, you can point a light at the background. Even a black backdrop can be interesting if you shine a light at it. A bare speedlight and a color gel, pointed at a black backdrop, can make a really cool background.
A few thoughts on modifiers.
Number one thought, modifiers are for controlling and shaping the light. Number two thought, bigger isn't always better.
You have three modifiers there that I can see, the shoot-through umbrella on the right, the little softbox on the left, and the snoot in the back. You can do A LOT with those three things. But to effectively use them, think hard about what each modifier does.
The shoot-through umbrella is the go-to modifier for many starting portrait photographers. It has its uses, but I'm personally not a huge fan of shoot-throughs. They're really hard to control. The when the Speedlight hits that umbrella, the light goes EVERYWHERE - the subject, the ceiling, the floor, the background. When it hits the ceiling and floor, it'll bounce off and go every direction again - not necessarily a bad thing, but definitely a bad thing if that's not what you want. If you place it close to the subject as your main light, the center will create a hotspot with rapid falloff (less bright as you move away from the center). This is good! Or this is bad! Depending on what kind of portrait you want.
The softbox is much more controlled and directional. Size-wise, it's a little smaller, this isn't necessarily a bad thing. The little barn-doors flaps on the side will further reduce uncontrolled spill. The flat surface will give a more even light, especially with bigger softboxes. It won't have as much of a center hotspot as the shoot-through umbrella, but at the edges of where the light touches, it will fall off almost immediately. I like softboxes. When shooting with Speedlights, I use one pop-up "brolly box" style octagonal softbox as my main light, sometimes a second one as my fill.
The snoot is easy. It puts a dot of light right where you point it, and nowhere else. Little spill, little uncontrolled bounce.
OK, let's go to some specific setups.
Here's a one-light setup, using a 22" square softbox. Considerations:
- Though the softbox is somewhat directional, I'm still going to get a LOT of spill and bounce from the ceiling, the backdrop, and the white floor. I don't need a fill light.
- Since the subject is in high contrast to the background, I don't need an edge light or a kicker light to make separation. In fact, an edge light might make her even less defined, since it would put a white edge against the white background.
- The light is on a boom directly above the camera. It's a studio strobe, but for this purpose it doesn't matter, a Speedlight at high power in a similar softbox would have achieved similar results. Not enough power? bump ISO from 100 to 200, it'll be OK.
Here's behind-the-scenes, click through for my crummy Photobucket, sorry I don't have the softbox in the shot. The top edge of the square softbox is right up against the ceiling. This is in my living room, we shove all the furniture out of the way and roll out the white paper, and lay down white tileboard for a floor.
Analyze this photo. Look at the shadows cast by her chin onto her neck, cast by her elbow onto her hip. Shadows cast by the "floating" wall tiles onto the paper backdrop. These are all an indicator of the position and size of the main light. The shadows aren't pitch black because there's a lot of light bouncing off the ceiling and floor onto the subject, to fill them in.
IMAGE LINK: https://flic.kr/p/DNjLSu Vita_Red_20160118_7157.jpg by
Nathan Carter, on Flickr
----
Here's another one-light setup, at the opposite end of the portrait spectrum, dark and gritty instead of bright and glam.
- This is a single bare Speedlight on a stand, for a very hard-edged light and deep shadows. I, uh, started out with a brolly box on a stand, without a sandbag, and a gentle breeze blew it over after five minutes. Oops. Well, bare lights work well for this subject matter anyway.
- I would have loved to have a kicker light for a little additional drama, but I was traveling light and not carrying much gear.
- I'm using a medium shutter speed (1/50) to let in a little ambient sky.
IMAGE LINK: https://flic.kr/p/yYhYdc DragonCon_20150906_4904.jpg by
Nathan Carter, on Flickr
Look at the very hard-edged and dark shadow cast by his nose, and by his chin onto the jumpsuit, the tiny catchlight in the eyes, and the defined skin texture. These tell you that it was a very small light source, and no fill light.
-----
Here's a two-light setup: Main light is a Speedlight in a 42" brolly box, rim light is a bare Speedlight. This is my go-to 2-light setup when I want to travel moderately light.
Considerations:
- The background is fine for this subject matter, I don't need to light it and I don't need to stop my light from falling on it. It's there.
- I want to use a relatively large light source for a more flattering beauty-ish portrait
- The kicker light adds interest and definition. I don't NEED it for separation from the background, but I want it for added visual interest. An orange gel on the kicker adds just a little more.
- Shutter speed is 1/160 (max sync), f/5.6, ISO200, which is just enough to eliminate all ambient. I could have gone f/4 and ISO100, f/5.6 gives me a little more DOF cushion in case focus is slightly off, while still blurring the background.
IMAGE LINK: https://flic.kr/p/uUeXvJ Metrocon_20150613_0082.jpg by
Nathan Carter, on Flickr
Look at the shadow cast by her nose. It's pretty dark because I had no fill light, but the shadow edges are soft because of the relatively large size of the main light. The large light also helps to minimize the appearance of any skin texture. This is not perfect butterfly lighting, I could have moved the light a little to the left or had her turn her nose a little more camera-right.
----
OK, now the big finale: here's a three-light setup, using gear that's almost identical to what you posted. Considerations:
- I have a black backdrop (black painted plywood box around the A/C equipment).
- Plenty of physical distance to separate the subject from the background
- A relatively large main light, my good ol' 42" brolly box, for flattering "beauty" portraits. (Beauty is in the eye of the beholder, eh)
- Kicker light in a shoot-through umbrella (one of the few times I use this) for a widespread kicker
- Look what you can do with a black backdrop - you don't HAVE to let it fall to black. Background light on high power with a colored gel on it. This is a bare Speedlight sitting on the floor, aimed up at the background plywood. Or, instead of the floor, you could put it on a stand directly behind the subject, pointed at the background. I might not put it on a stand off to the side, since it'd be hard to get an even light across the background (the side nearer the light will be brighter).
- The "backdrop" plywood is pretty small, but I want distance separation between the subject and backdrop. By standing very far away and using a long focal length, I can use perspective to make this work. If I tried to stand close and use a wider lens, the background would not be large enough.
Setup/BTS. The subject stands where my colorchecker/gray card is sitting on the floor. Right at the back edge of the stage is my background light, pointed up. The shoot-through umbrella is pretty low power, just enough to give a hint of additional interest coming in from camera-left, but not enough to spill all over the place.
IMAGE LINK: https://flic.kr/p/pUw9Xz BBB_Cabaret_20141031_30909.jpg by
Nathan Carter, on Flickr
Results:
IMAGE LINK: https://flic.kr/p/pCikMu BBB_Cabaret_20141031_30913.jpg by
Nathan Carter, on Flickr
The face lighting style is loop lighting, but since the modifier is large (relative to the subject), the edges of the nose shadow are very soft. Also note the very subtle orange glow on the subject's right, frame left.
Blue gel on the background light instead of orange, and the light is aimed a little lower to get a gradient effect. I don't think I had a gel in the shoot-through this time, or maybe it was blue too, I can't remember.
IMAGE LINK: https://flic.kr/p/GN7DgX Cupcate_Burlesque_20151120_5894.jpg by
Nathan Carter, on Flickr
Since her chin and nose are pointed up, there's no significant nose shadow, just that little sliver of shadow on the side - so this doesn't really count as classic butterfly or loop or anything. Still works, though.
Anyway. Flip through my Flickr if you like, and the albums in my Victor Voyeur page, I'm happy to answer questions about any of the photos in there.
