Actually I think that this subject would be a great exercise for us. And if you think that a 3d render alone can “only” give you photo real results you haven’t been using 3d that long. It is possible to composite realism in a basic 3d render using Photoshop or Gimp, etc. It has been done for years by 3d artist.
Maybe we could pick a reference image that is a real world photo and lighting involving something like wood blocks, glass marbles, nails or concrete covered pavement. Such elements are not hard to model and the textures are easy to duplicate with photos from the web. We could set up a scene of a collection of real would elements and place them inside of a box (Cornell box so to speak). Then we could put this collection in good but simple lamp lighting, etc. and take a digital photo of it. Finally we could try to duplicate this real photo with Blender, Yafray, AO, etc. We could also list the methods that we used in detail and the render times, etc.
This could result in helping some of us to find to the best path to achieving 3d realism in our own renders.
Everything from light intensity to shadow depth can be tweaked in a 2d app with the use of multipass rendering or rendering out to separate elements of your image in different secularity, shadow, diffuse passes.
Sometimes more often than not photorealism in 3d is achieved with multipass rendering compositing techniques. And we can mistakenly attribute this quality to the power of a tweaked “scanline” render pass in a 3d software app.
AO rendering , Yafray, Mentalray, V-Ray, etc. can allow just about any artist to render something good without all the tweaking and compositing. This is also known as 3d lighting, texturing and compositing skills. But Yafray rendering, etc. can take up precious time away from your project. Multipasss photorealism is way faster than Yafray or AO rendering. And with Blenders improved raytracing engine multipass rendering is so much better now in Blender.
Right off the top, using real photo textures, diffuse, and spec maps in your work and a good study and application of the lighting principles that are found in the real world can give you photo real results. All this can be done without the wait that tweaking and rendering that Yafray and AO renders involve.
Did you know that most seasoned 3d pros don’t rely on the power of a 3d software rendering engine to produce 3d realism all of the time? They do rely on their practiced and speedy methods of multipass rendering and compositing.