Details and Contrast
In this phase I was focusing on adding small details like wires, tubes, tools, etc...things that would contrast with larger areas of low detail. I usually try to create contrasted areas in a painting so that the viewer has a dynamic perception of the image. Try to introduce contrasts and a subsequent balance between large soft areas and smaller defined details, dark/light, warm/cold, small/big, etc (Fig.10).
I hit the painting once more with the Color Balance filter. I picked colder hues for the shadows and warmer ones for the highlights. I love this filter as it harmonizes the color scheme and automatically adds contrast to the image. I also created a new layer in Color Dodge mode and with a large soft brush and a dark brown color I introduced glows from the lights in the back. Objects like the mechanical arms which form dark silhouettes against bright areas are excellent for these soft glows. I tried to keep them subtle, though (Fig.11).
Final Detail Pass
With a small brush I started zooming in on areas where I could add all kinds of details, like knobs, wires, highlights, batteries, wrinkles, lights, etc. Large shadowed areas are also a great place to introduce soft details. These details are not perceived right away, but they can be quite rewarding to the viewer upon closer inspection. I also introduced a separate layer for the down lights. Lighting effects like glows and volume lights always add interest, but try to keep them low profile as they shouldn't detract from the main subject and light sources (Fig.12).
Finally I added my signature and applied a Smart Sharpen filter. Sharpening should take into account what the final resolution of the image is going to be. Since this one was created mainly for web display, I resized it to the desired resolution and reapplied the Smart Sharpen filter to bring out the details and brushstrokes at this final resolution. Don't underestimate this pass as it can make a big difference (Fig.12).