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Avi Liberman
•
2yr
added comment inWhat is Light?
Dorian - I have a small confusion some things and I just wanted to make sure I got it.
First, why do needs to know about "diffuse reflection" in relation to shading? Isn't what makes the form 3d is where the light hits (reaches) its surface?
1. When you showed specular reflection, you used a mirror or chrome.
Does it mean that all the lights gets the same value on every point of the ball because of the surface material? Does specular depends on the material or surface angle?
2. About the highlight. Why do we see highlight on rough surfaces (not chrome like) like body? I understood that it relates to specular reflection.
@squishygian
3mo
Hi Avi, I had the same question as you, it seemed contradictory with the information given and the examples like a chrome ball, that an incredibly smooth surface like say a perfectly smooth white marble will still have diffuse reflection as well as specular, I read this article on Wikipedia https://en.wikipedia.org/wiki/Diffuse_reflection#:~:text=A%20flat%20surface%20is%20indeed,continues%20to%20be%20diffusely%20reflected.
that made it a bit clearer, apparently diffuse reflection happens just below the surface of an object, the light penetrates the object, and sort of bounces around inside and goes everywhere, there are very few materials that don’t allow this to happen, one being chrome, specular reflection on the other hand, happens above the surface, so let’s take the chrome ball as an example, chrome and other metals do not allow light to bounce below their surfaces, so no diffuse lighting, but because specular reflection happens on the surface, it has specular reflection, hope that made sense
TLDR: According to physics, materials that can be penetrated below the surface by light will have diffused reflection, if the surface of that material happens to be smooth, it will also have specular reflection because that happens on the surface, not below it.
@pizzle
1yr
I'm not sure if you are still wondering about this. I don't yet have this course so I don't know if some post are hidden to me or not. But as a professional photographer, I can answer this to some extent for you.
I think it is very important to learn about "diffused reflection" in relation to shading, because it's all light and has an affect on what we see. But to clarify, don't think of diffused and specular. There's direct light, which is often your main light source, and then there's bounced light, often used to fill in shadows (you can also use another direct light source to fill in shadows).
Both the mirror and skin (or any other surface) are both bounced light sources. The direct light would be (in this case) a laser, or to better understand, think of the sun or a light bulb in your home. I can create specular highlights without a mirror, so it isn't needed. But a mirror would give you a stronger bounced reflection and light source.
Just about everything will bounce light back off of it and create a secondary light source depending on how strong the main light source is. as a test, go outside, turn your hand flat and look at the underside at the shadow, then take a plane piece of paper and start to bring it close to your hand, you will see the shadow get brighter.
The lingo could be confusing for some. As a photographer, diffused light is related to the kind of light. The sun, a bare light bulb are both considered hard light sources. Put a cloud between the sun and object or a lamp shade on, and they both become diffused light sources.
Specular would be the considered the type of light reflecting on what we are looking at. And in a way, yes, it is the bounced light we see off that surface we are looking at.
Hope this helps clarify things a bit.
