Upload & Sell: Off
Here are two quick examples.
I used Photoshop and did the following:
- Opened base image.
- Created a new blank layer above the base image.
- On the new layer, I did a Filter>Render>Clouds (making sure black & white were my foreground and background colors).
- Repeated Filter>Render>Clouds, if necessary, until it contained a steam cloud more or less that I liked.
- Used the Magic Wand tool to select a steam cloud out of all the cloud clumps. I selected the more-or-less brightest part of the cloud and I adjusted the Magic Wand Tolerance to adjust how big of a cloud was selected. You can also use Select>Refine Edge to adjust the edges of the could.
- Did Select>Inverse to invert the selection followed by pressing the delete key to delete everything but the steam cloud.
- Used Edit>Free Transform to move the steam cloud roughly where I wanted it and to rotate it.
- Changed the Blend Mode of the steam cloud layer to Screen.
- Created a Curves adjustment layer above the steam layer and then right-clicked the Curves layer to make it activate the Clipping Mask (makes the Curves layer affect on the layer below it instead of all layers below it).
- Adjusted the Curves to bring out the "cloudiness" of the steam cloud.
- Added a mask to the steam cloud layer and used a very soft, black brush to soften the edges of the cloud and to erase any parts that I didn't want.
- Used Edit>Transform>Warp to warp/shape the could if necessary.
- Adjusted opacity of the cloud layer to taste.
It's not as complicated as it looks if you have some familiarity with Photoshop. It took me longer to write up the steps than it took me to do them on both images. As always in Photoshop, there are probably another 20 ways to do steam. I just did a quick Google on "photoshop steam" and turned up several tutorials. I also tried something quick in Lightroom to see if I could do something similar but didn't have much luck. The Adjustment Brush in LR doesn't really have a "Screen Mode" so even using a brush with boosted exposure and shadows doesn't really give the same effect.
One key thing I think is to keep the effect pretty subtle. That helps the realism IMO.
Hope that helps.