Since Carrara is currently rendering something, and I rarely have the time anymore to experiment myself, I figure I'll just ask you guys.
Photon Mapping- What is it, and when should I use it (as far as realism goes)?
Transluscency- How do you get this to work? I tried for about an hour to make a teapot transluscent, and just could not make it work. And if I have SSS, am I going to need transluscency enabled, too (like for the ears)?
Finally, what settings do you use for realistic, wet, lively looking eyes? Is SSS involved here, too? And am I going to need to make my own if I want them to be believable (You know, an eye that's not just a sphere with a texture, but an actual structure like the ones Shonner made)?
Okay, one more thing, BRDF and BSSRDF- I'm pretty sure these have something to do with how light hits a surface, but other than that I'm clueless. What do they stand for, and is it anything that can be manipulated inside Carrara 5?

This is just an experiment I did. With light through transparency set for the rendering, look at the differences when Translucency is set at 0% and again at 100%.

Compare these results when the translucency is set at 0% and you vary  transperency between 0% and 100%.

Hope that helps with one question.

Thanks bwtr. I was rendering with only an hdr, and either translucency requires more/different lighting, or the effect is just too subtle to notice with hdri alone. Now I'm trying to find a way to create a falloff with the translucency, so it only goes to a certain depth (from what I can tell it goes the whole way through).

I think, with translucency, you need light coming through from behind to get the effect. That effect I did was jus on a plane. If it had thickness would that make a dofference.

You may need to look at the SSS (sub surface scattering) mabe to get a "depth" effect?

It would be good if Shonner replied to this thread for you.

Have a look at the shaders which come with C5. May help.

So far I've been testing using a "fleshy" sphere, with a smaller black sphere inside, and the ring shape light. I get a funny looking effect  on the flesh sphere where the black sphere blocks all the light, so the object only looks transparent in that area. Maybe I should try placing the spheres and light inside a cube so the light can bounce around more and perhaps counter the effect. I'll post some images to demonstrate when I get back home.
I've been searching other forums trying to find out more; some of their results really make my stuff look like child's play- 
http://forums.cgsociety.org/showthread.php?t=377706&page=6&pp=15&highlight=translucent

Was this what you have been looking at?  Did you find anything about "Bidirectional surface scattering reflectance distribution function"?  Lets know if you did please

Attached Link: http://http://www.onona3d.com/pdf/texturing.pdf

This should provide our answers?

Attached Link: http://http://forums.cgsociety.org/showthread.php?t=77484

Extended versions are here.

wow, you've been working! Here's a small comparison of tests I did today, focusing only on the diffuse, translucency, and SSS parameters. The setup consists of an outer sphere 1 unit in diameter, an inner black sphere 1/2 unit in diameter, and a single ring light shining from beneath.

1: Diffuse set to a lime green color, translucency set to a value of 90%
2: Translucency changed to 5%
3: Inner sphere set to 90% size of outer sphere
4: translucency of outer sphere changed to 900%
5: Translucency changed from a value to a color, the same color as the diffuse
6: Diffuse color set to white (this gives a result similar to the first test)
7: Translucency set to blue
8: Inner sphere color changed to red
9: No diffuse setting used, translucency changed back to lime green, SSS enabled. The following is all set within the SSS's parameters- Tranlucency- 10%, Refraction Index- 30%, Intensity 100%.
10: SSS intensity changed to 20%
11: SSS translucency set to 90%
12: SSS intensity changed to 100%, inner sphere diffuse set to lime green.

You know what, I just remembered I did hide the inner sphere at certain points, but I don't remember when... my bad. The dull cap on the top was really starting to bug me. Here's a small scene to see the translucency (god I'm getting tired of typing that word) from different angles. Back wall set to glow and lit with anything glows, the only light source in the image. And I don't know why I have those annoying artifacts on the side walls, the ceiling had it too until I added objects there, as well.

Oh right, and good find on the bssrdf; what page was that on?

I can not remember now but it apparently refers to Aniostropic lighting. (See in Carrara shader list options "Lighting Models>

You have been busy also.  Whats the reason for having the inner black sphere though?

I wanted to see what effect an interior structure would have on the light as it passes through, as these tests are primarily, for now, an attempt at building a better skin shader.

What happens if you create a sphere in the vertex room and add thickness? Might this approach an impression of the model haveing "bones"?

Vertex sphere with 0.5" thickness. Added back light.  Ist texture (as added_ Metals>(the antioscopic)Brushed Copper. Agjust add SSS(default Settings)Adjust transparency to 28%

Getting interesting?

I hadn't thought of that, that's interesting. I think I'll try some tests with V3, as that will likely be easier to judge for accuracy than the sphere.

I am playing around with one of the hands from Poser. Converted into a mesh and added thickness in Carrara. Will have to add a hand skeleton to it I think.

All interesting fun.

I made some progress tonight. My first attempt (1) turned out the best. SSS is activated and everything but it's intensity and color are set default, and the translucency channel I've set to color, using the same color the SSS employs (a dull red). Image 3 is the same, but translucency (in the translucency channel, not the SSS channel) is turned off. In the center, image 2, I've raised the SSS channel's translucency from 10% to 90%, thinking perhaps I could get a result more like the first without fiddling at all with the main translucency node. As you can see, this isn't the case. So I think I'm closer now. The color in the first image seems close to accurate, but I need to tone down the intensity. Holding a light up to the back of my ear, I see it's mostly the "interior pools" (I don't know what they're called) that are lit up enough to see blood, not the outer rim of the ear. How do I place both a color and value in the translucency channel? I'm sure it's very easy. What kind of results are you getting bwtr?

I have been sidetracted elsewhere.  Your no1 result looks perfect. Will try myself later today.

The skin coulour and gloss is not right yet but your No1 settings look fine to me.

When I get a moment I will do a skin with veines and try again

Here is my veined skin you might like to play with.

This mornings first try!

Not bad! Been busy with work lately, but when I last tried a different angle with the best settings from my last posting, I found the translucency affected practically every part of the body facing the camera, reguardless of thickness. Either I'll have to try another setting, or create a map for translucency.
I'm guessing it's possible that C5 can't determine the amount of translucency relative to local thickness, but I don't know for sure yet.

Carrara does not do SSS on ears well.  Maybe Carrara 6 will have an advanced SSS that can handle thin protrusions from large dense objects similar to modo's SSS?

Nice skin, bwtr.

Thanks Shonner.  Inspired by all your works!  Difficult business I have found out.

Happy New Year mate.

I decided to have a hand at the eye shader tonight. Shininess and highlight are set to 100%, reflection is set to 5%, and a subtle noise (fractal if I remember correctly) is in the bump channel. The eye is really just a sphere with a Poser character's eye texture projected over it, so there's no realistic structure, just textures. Illumination in this first image is only two self-illuminated cubes.

and here is the same setup, with box lights in the same place, only with an HDR file for more immersive reflections. I'm sure reflection could be set even lower, perhaps 2-3 percent.