In this tutorial I will present some basic post production techniques that may improve the final look of your renders. I was using Photoshop CS4 but most of the presented tricks can be achieved in any decent 2D editing software.
All we have is just a merged RGB image, without any render passes such as reflection, specularity or object ID. First step will be changing the coloristic mood, so we use Color Balance adjustment layer. But before we start it's good to change our working color depth from 8 to 16 bits per channel. Remeber that if you want to save your final output as jpg file, you need to get back to 8 bit mode again.
(Where to change color bit depth.)
(Color Balance adjustment layer.)
(Color Balance setup.)
Image seems too dark in the centre, so I need to enhance exposure a little bit (I use exposure adjustment instead of Levels or Curves, as it gives me more tonal controll). Once again I use adjustment layers and create one that would darken the whole image even more, and the second one lighting up the centre.
(Exposure adjustment layers.)
(Second Exposure adjustment layer setup.)
Next step is boosting model's reflections. To do this, I must merge all the layers and then duplicate the merged one. Desaturate it and set the blending mode to Color Dodge. Add black mask to the new layer and paint reflecting areas (over the mask) with white, soft brush (brush opacity 10% - 30%). Play with the layer's opacity to adjust reflections way you want them to look like.
(Step by step color and tonal adjustment.)
For sharpening I use common technique with High Pass Filter. Flatten your image once again and then duplicate merged layer. Go to - Filter - Other - High Pass filter - and set the radius from about 2.0 to 3.0 pixels. Press OK and set the blending mode to Overlay. You can create a mask and erase areas with antialiasing problems.
And we're almost done here. You can play with Levels adjustment if the image seems too bright, too dark or out of contrast. One more step I usualy take is using some of the Nik Software - Color Efex Pro filters. You can download them from the producer's website and test for free for about two weeks.
(Color Efex Pro filter manager.)
I've used Tonal Contrast filter to extract even more from the shadows and increase the contrast between the grayscale tones.
And that's it. Final touch would be "Lens Correction filter" simulating some physical lens effects like chromatic aberration, vigneting or optical distortion. Try not to overuse them, as for example images with exaggerated chromatic aberration may only seem more realistic, while they still look very amateurish. As you can see, the post production used in this project is rather subtle. Although each single step may seem not to make any significant changes to the base image, after merging everything into one output we can see how much difference there is. My secret of post production is taking some time for experiments and making small steps in the whole process. Usualy ending at adjusting just some basic parameters such as brightness/contrast, tonal curves or color balance, hardly ever brings satisfying results (especially if the render has poor quality). Techniques shown in this tutorial are not really anything special, but still I hope someone will find them useful.