I've covered this at more than sufficient length
elsewhere, but I still get asked about lighting in Iray, so I wanted to do a quick set of text basics for those who have trouble ferreting out the relevant bits from the videos. Here is a reference set of lights
and a Sunny 16 preset you can download and use for practice. These are the lights I use as starters in 90% of scenes now. If you want to know more about tone mapping I've gone into that here
as well.THREE-POINT LIGHTING: WHAT IS IT?
Wikipedia covers the photographic theory of three-point lighting here,
if you would like to know more about that. The short version is that when you're photographing or rendering a person, your scene can look nice with less effort if you use three lights arranged around your subject.A KEY LIGHT
is a bright light, usually white, in front of and slightly above the level of your subject's face.A RIM LIGHT
is a slightly less bright light, usually yellow or orange, behind and slightly to one side of your subject, creating a warm "rim" or halo around them. A FILL LIGHT
can be a couple of different things. It can be a light off to one side and in front on the opposite side from the key, or it can be a "bounce board" near the ground that reflects light up to the subject. Usually it is lower than the key light (although I personally don't always do that) to ensure there aren't harsh shadows on the chin area and lower face.
APPLYING THREE-POINT LIGHTING IN IRAY 1: Loading Spotlights
The easiest way to do this is with photometric spotlights, using an HDRI for additional fill (in much the way that an outdoor shoot uses natural sunlight for fill as well). You can use mesh lights, too, but I'm not going into that today.
Suppose you have a figure centered in your scene. You need to create three spotlights from the "Create" menu on the top of Daz Studio, Create--New Spotlight.
When there are three spotlights in your scene, the fastest and easiest way to arrange each one is to select it and look through it. Go to your Scene tab. If you don't have one, you can create one using Windows--Panes/Tabs. Left-click on a spotlight to select it. You can also rename a spotlight by clicking and holding on its current name in the Scene tab if you want to name them Key, Fill, etc.
With the spotlight selected, go to the top right portion of your 3D Window. There you will find a dropdown. Right now it probably says either "Default Camera" or "Perspective View." Either way, click on it. A dropdown appears showing all the non-mesh lights and cameras in the scene. Select Spotlight 1 (or whatever name you gave it).
Now you are looking through the view of that spotlight. When you use the movement controls just below that dropdown, you are moving the light itself, not just the view! So when you move the controls around to frame your figure in your view, now your spotlight is pointed in the right direction. Move this first one so that you are looking slightly "down" on the figure from the front and right or left. You don't want it to be looking straight on from the front because it will create a "headlight" look. This will be your Key.
Go to the Parameters tab with the light still selected. Under the Light heading are your photometric light controls (scroll down). The important things start with Light Geometry. Leaving this at Point will create a small, sharp point of light, like a flashlight. I recommend changing it to Disc to create more of the look of studio lights with reflectors. Then below that are parameters called "Height" and "Width." These determine how big the light object will be on rendering. I set them to 50 each, but you can experiment. The bigger these numbers are, the softer and more diffuse your shadows will be - only use 10 and 10 if you want fairly sharp, harsh shadows!
Below that, turn off Render Emitter and Two Sided. Those are not useful in most scenes. Render Emitter will make your spotlight visible to the camera and Two Sided makes the geometry shine out both directions if it has them.
Luminous Flux (Lumens) determines the brightness of your light. How much you need here varies directly with how far from your subject your light is going to be, but it always needs to be higher than the 1500 default. The numbers I use for Sunny 16 tone mapping (discussed below) are usually around 150000000 to start.
Last of all is the Temperature in Kelvin. Real lights actually have temperatures, which you can find if you Google them; for now the important thing is that temperature controls color. The default of 6500 K is white; 3500 K is warm and orange, and dimmer; and 8000 K is very bright and slightly blue. For now leave this Key light at 6500.
Now that you've set up your Key, select the second light, which will become your Fill. Move it to the front and opposite side from the Key and repeat the steps to give it geometry and more lumens (although I would give it less than the Key by at least a power of 10). I often tint this light blue, not just using 8000K as a temperature but also using the "Color" option at the very top of the light controls.
Finally, position the Rim light behind and facing your character. This light should be about as bright as the Fill in lumens, but at a temperature of about 3500 K to make it warm and orange. You can use other colors or temperatures of rim lights, but this works for most scenes.
Now you have your lights in place, let's set up the Tone Mapping and check the HDR.APPLYING THREE-POINT LIGHTING IN IRAY 2: The HDRI Or Sky And Tone Mapping
The Tone Mapping settings are found in your Render Settings tab. When Iray is set as your render engine, a Tone Mapping heading appears. The important values for today are Shutter Speed, F/Stop, and Film ISO. I'm not going into what they mean in detail (again, the Tone Mapping tutorial was for that), I'm just going to recommend that you set Shutter Speed to 200, F/Stop to 16 and ISO to 200. There are other ways to handle tone mapping, which are discussed in the other tutorial, but this works for most daylight indoor and outdoor scenes.
The default HDR in Daz Studio is perfectly fine. It's not fancy, but it's a reasonable color scheme for most lighting setups. If you just ignore it your scene will probably come out decent. There are ones sold in the store that are much better as backdrops or skies, though, so if you have a budget for it I'd look at Dumor3D and DimensionTheory's stores (OutOfTouch has some nice outer space ones, too). Lately I'm using Skies of Iradiance or the Light Probes the most. Mostly with HDR you don't need to tweak settings a huge amount, just click and go. If you want to turn the HDR's intensity up or down, or see what it's currently set, you can find this in the Render Settings under Environment. Make sure Draw Dome is set to ON if you want to use the HDR as a sky or backdrop.
If you are doing a daylight scene that only needs a sun, you may also think about using the Sun-Sky system instead of an HDRI. You can do this by clicking on the current picture by the words "Environment Map" and choosing "None." This will expose the sky settings. Again, make sure Draw Dome is ON.
By scrolling down you can set the time, date, latitude and longitude if you want to match a particular time and location. Changing the time moves the "sun" around your sky. You can also set a spotlight as a sun node by adding another spotlight to your scene and then clicking the "SS Sun Node" button in Environment. This lets you choose the spotlight in your scene as the "Sun." Then when you move the spotlight, you move the sun. This can be easier than trying to get the sun placed just right using time settings.
I like to also turn up the "Horizon blur" setting when using the Sun-Sky, because otherwise it's a bit of a hard line and can look odd if it should end up in the background of a scene.
You can use the sky system for night as well by setting it to a late time, but it will have no moon or stars, so I recommend using a night sky HDR in that situation instead.
APPLYING THREE-POINT LIGHTING IN IRAY 3: The Headlamps
Finally, make sure the headlamp of any camera you use is OFF! Select the camera in the Scene tab and look at it in Parameters Tab. There should be a set of settings, and the bottom one is labeled "Headlamp." Click on that and you will see a dropdown that probably says "Auto." Change it to OFF.
This is important to not have that unwanted shining light from your camera, and also is the reason why you should ALWAYS create a camera to render through and NEVER use the Perspective, Front View, etc. cameras whose settings you cannot access - their headlamps can't be turned off!