File [attached]: Use it like a “sand-box”. Explore it, tweak it and take what you need. :o) ...and yes, there are too many ideas in it.
Photorealism is a term that I avoid, it is too bendy, and clients might have a different idea about it.
However, observation is the “mother” of it. A good skill-level in photography is a must have (not just a click away and fix it in Light Room stuff), so one knows what happens to light (and how light, surfaces and camera works together). There are no short-cuts for this. YOU have to learn it. A good starting point is certainly the list in the material editor, write it down and explore your surrounding [objects] with it, what part [material editor] would be useful. Then do the same thing with light, there are over “hundred” parameters and options. Know them, and explore the objects again. Then get the options in rendering - same procedure. As a 3D-Artist that is the base to know., if that level of realism is targeted. With this in mind, the camera position and settings are critical to work with—in the same way.
Of course, just suggesting this and not delivering would be weird. I started to post some stuff “Photography for 3D Artists” here:
https://www.youtube.com/c/drsassila
As long as we do not have a frequency based light system, C4D is R-G-B based, we will not be able to reproduce, e.g., how light really behaves in a lens.
Your request: Too little information (above) was given (e.g., context, what materials, is it glass, acrylic, etc.), to get closer, and as you can see—a simplified file is possible as well. CAD files are more often than not, not at all a start for the quality you are aiming. Yes, I do not have seen what you have. As usual, you do not share and request support. We have been there many times…
Scale is certainly a factor in that set up as other parts in the scene, as light sources, objects, etc.
(…)
I would go with a multi pass render and a good color -grading/finishing. (Render in 32bit/channel, float—of course), for multipass and some light glow effects, I made [back in time] a series and not so much has changed since. It’s here on CV.
With the complexity of that theme, for starters I would suggest the book from PIXAR’s crew:
Digital Lighting and Rendering (3rd Edition) (Voices That Matter) Nov 21, 2013
by Jeremy Birn
(I have read the first and second edition, but flipped through the third. Certainly a good base to have)
All in all, you might suggest this as a tutorial series. Perhaps someone is brave enough to go through this theme completely (if that is even possible)—and not just for a single object, scene, a series that creates a base for this kind of quality. It will be perhaps a work of many years to train all the skills needed to produce “photorealistic” results for anything that is thrown as challenge at an artist. It will be an “master/apprentices” kinda series, as a simple “do-this,do-that”, style will not work at all for this, never has, never will.
Take care.
[edit, Jan 17]