Some basic tutorials about lighting

Rafael

I am preparing some small and basic tutorials, so hopefully, you will find them useful.

Here is the first one on How we can have more consistent illumination in our renders.

https://otake.com.mx/Tutorials/Light-Intensity/Light-Intensity-Inside-DazStudio.php

In photography, we use either a light meter or a gray card. I prepared a simple scene with a couple of spheres as gray cards.

In the tutorial, I explain how to use them, how to interpret the readings and some recommendations on the default values of the lights.

It is a work in progress. I will probably expand it with new tips.

Feel free to comment if it is not clear enough.

Rafael

How soft a shadow produced by the Sun should be?

The relationship between how far a subject is from its projected shadow (C), and the falloff of the borders of the shadow (D), is the same as the relationship between the light source diameter (A) and the distance to the subject (B).

In the case of sunlight, we are tempted to think the shadows are just harsh, to think that the sun is a point of light, but it is not. The diameter of the sun is about 1.4 million kilometers, and the distance to us is more or less 150 million kilometers. This is a bit more than 100 times the diameter. This means that the softness of the shadow is more or less 1/100 of the distance to the subject.

In our renders, this means that if we want to simulate the sun coming from a window, that is 2m away the fall of the shadow should be 2cm. This should be important, especially on close-ups, because 2cm is close to the size of the distant phalanx of our fingers. It will be an important element to give our renders scale.

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Here is a simple scene. A wall rotated to be perpendicular to the sun, a plane located 2m away from that wall (E), and sunlight provided by Sun-Sky options in Daz.

And here are two renders. The first one the soft zone is out of scale. It is too soft, so the shadow looks like coming from an object further away than actually is (F). The shadow of the hand is too soft for that short distance.
The second is closer to what we should expect. About 2 cm on that shadow of the wall 2m away (G). We can see how important this is to be consistent in the scale of the elements in our render.

The default settings on the Sun Disk Scale slider on Sky-Sun parameters is on 4. Change it to 1. But also, the softer look of 4 is a nice touch in some situations.

Rafael

Use extra lights!

In real life photography you add more lights as you need them, you can carry a portable flash, or a white or silver reflector. Don't be afraid to add an aditional light at your scene.

A. The image on the left is a difficult scene in real life. Combining direct sunlight with some areas in the shade. I am using "Sun-Sky" as lightsource.
B. It is a good idea to add a simple light to light up our character. I added an area light and now using "Dome and Scene", so both, the Sun-Sky and the area light contribute to the lighting.

But you can also add lights using HDRI to balance and control the scene.

C. Here is a simple scene using one HDRI. It is consistent, but the image can be improved.

D. I reduced the intensity of the HDRI from 1 to .3 so we do not overexpose our image.

E. And I added two lights. One area light (E), as a flash from a photographer would use. (The same case as the previous example)

F. And a point light, on more or less the same position the natural sun would be. This "Fake-sun" give more light to our subject but maintains the original sun position and shadows but without increasing the background brightness.

G. We can see the combined lights. The HDRI, the area light and the Fake sunlight. The overall image has the light more balanced and integrates better the model to the background.


 

So, don't be afraid to use more lights!

robertswww

@rafael_f12aa018 I am enjoying your clearly explained Lighting Tutorials, and I really like your photography comparisons and the accompanying example images showing each change the different lighting effects have on a character and scene. Keep up the good work!

Rafael

Thank you!

Artini

Great examples.

How did you find the position of the additional lights to be consistent with the HDRI one?

I have tried myself, but could not find the really convincing positions of the additional lights.

 

Rafael

Artini, Nice question.

How do you add a point light consistent with a light on an HDRI?

1. Turn "Draw dome" ON.

2. Add a camera with a wide-angle lens, say 20mm. Position it more or less on the opposite side of where the HDRI source of light might be.
I added a sphere just as a reference point on where our subject will be. Use Iray render mode to see the shadow.

3. Select the camera and move it using the View Orbit and Move tool Find the source light of the Hdri. Position it behind your center or point of interest. In this case the sphere.

4. Switch to wireframe mode and add a point light on more or less the opposite side of the camera. I'm using the top view.

5. Switch to Camera View again and fine-tune the position of the light using the gizmo.

You can play with the values of your new light. I Would keep the temporal camera to fine-tune the position of the new light.

Additional Tips.

a. If you use a Spot Light, use the same method, but at the end, you can choose it as a "camera" to point the light toward your subject.
b. An extra advantage of using a spotlight is that you can dolly it using the blue arrow, whereas a point light is more difficult to control without the usage of the temporal camera.
c. If your scene is a close-up scene the lights can be relatively close to the subject. The bigger the scene the further away the light should be. This is because an HDRI illuminant is in theory an "Infinite sphere". In Daz Studio there is a slider for Dome Radius. I have not tested much on how important this is. I think this affects the softness of the shadow relative to the distance from the object to the floor (Related to my other post about the Sun soft shadow).
 

 

Artini

Thank you very much for the detailed description - much appreciated.

 

Artini

Any idea about how to incorporate a background images (no HDRI) into Daz Studio

to get consistent lighting in the scene with them?

 

Rafael

That is what most of my few renders on Daz has being about. I need to start my gallery!

This post is a Work in progress...

As this is a bit complex and a case-by-case scenario, consider this section as just some useful tips.

Matching the illumination with background images

Here are some examples of images I made combining a Photo as a background with a 3D character.

Under Edition...

 

 

 

 

 

Artini

Thank you very much for taking it into your consideration.