To make the lighting appear to be real you'll have to at least separate the cityscape into two elements, those in front of the lightning and those behind. Then you put the lighting between the two layers along with some light. The biggest trick is to make the project a 32bit app so that the lighting effects and wrap around the cut out buildings would look realistic.
A comp might look something Like this:
- Layer mask from a solid with feathered mask control the areas of the image that are effected by the flash
- Adjustment layer with the Exposure effect applied to darken the flash
- Another layer mask to define the layer of the backlight
- Your foreground element blurred and brightened to provide the light wrap around the buildings from the lightning flash
- Your foreground portion
- A solid with a duplicate of your lightning strike much brighter and blurred to provide a good glow to the flash
- Your original lightning flash layer
- Your background (the entire image)
This is the result I got in less time than it took to explain it.
Actually real lightnings are 70% "unatttached", because the origin point of the discharge is somewhere in the atmosphere (physically, lightnings bolt upwards, not down) or the lightning expands horizontally. Therefore them touching the buildings would probably not look right many times. Where I see a problem with your image is that the lightning itself is too fat at the end of its forks. Based on the above, the source point is invisible and light emission only increases as the plasma heats up the further away it gets. If you will, the ends would look more like fine hair that caress the buildings. Also, and Rick nicely caught this one, you have no atmospheric scatter/ cloud illumination. Even on realtively clear lightning storms you would see a lot random flashes inside the clouds that also reflect on the streets and building even if no actual bolt exits. You may therefore want to consider adding sporadic soft sheens in the buildings facades to bring it more to life...
This was very helpful. I created more layers and adjustment layers and the shot started looking better and better. I did thin the lightening strikes but couldn't figure out the way to get it to look thiner on the strike side and thicker at the point of origin.
Thank for everything.
"Realisitc" lightning is never convincing; audiences expect a stylized version of reality. You can research lightning flashes and many different types of atmospheric phenomena via google and youtube.
I work at an electrical utility and we do electrical arc animation every now and then. After shooting (really cool and exciting) sustained and instantaneous arcing on huge substation apparatus, we always end up using After Effects to do the fun stuff because the real arcs simply are not convincing.