What can I do, in terms of lightning, to make Digital look like Film? By that I mean a "dreamy" sort of look.
Does it has to do with the color temperature? the setup?
Each colour film reacts differently to light and renders colours in it's own unique way, if you are trying to accurately simulate film then you need to learn the properties of the particular emulsion.
However if you are trying to get a generic retro look to your images then this is much easier. I shot a wedding a few years ago and decided to do the whole classic film look to all of the images.
The main things to adjust are white balance and saturation, I tend to go for a very warm WB that looks both nostalgic and film like and the same time. For older films reduce saturation. Some times a bit of split toning helps, here I pushed the shadows toward magenta and the highlights toward cyan:
Another useful cue is shallow depth of field, most film images were shot with "full frame" SLRs or medium/large format cameras, and fast lenses were often used wide open due to the poor ISO performance of film, combined with a bit of film grain the look is fairly convincing:
An incidental, less clinical approach to shooting is recommended, film was expensive, you could rarely afford to just shoot a few hundred images and pick the best:
Finally the image content helps, look for retro vehicles/buildings, avoid people using smartphones etc:
Finally don't be afraid to boost contrast, it can look just as "film like" as low contrast instagram images, but don't overexpose and digital images feature hard clipping of highlights, film had a more gentle roll off:
There are so many different things that people refer to as "film look", rather than any one thing.
In truth, people have their own ideas about what "film look" is, and most of them aren't really anything to do with film vs digital. A digital camera with the same lens as used in a film camera could produce the same image, not accounting for any digital post-processing (some of which may be done in-camera).
"Film look" may refer to:
Applying less digital sharpening
The camera and/or RAW processor adds a lot of sharpening by default. Digital sharpening has a very characteristic look that you don't get in photographic prints directly from film. You can decrease this in the camera, and chances are even the lowest setting adds some sharpening (to counter for the Bayer filter).
Good lighting techniques
Sometimes when a scene is lit well in a studio, that can look like a "film look" because people associate digital cameras with amateur snapshots like on Facebook, etc.
Paying any attention at all to "strobes" other than on-camera "deer in headlights" type can get you this type of "film look" if it's done decently.
S-shaped contrast curve
Film's response to light tails off at both the top and bottom-end in an S-shape. Some of the higher-end digital cameras may be able to emulate this using contrast curves selectable in-camera, though this can also be done with the "curves" command later.
Sometimes "film look" is simply about grain.
Poor black levels
Instagram has taught us that boosting the black levels so that blacks are no longer black but a muddy grey, or even a muddy purple or brown colour, can achieve a look that mimics poorly exposed/developed older film (depending on how subtly this is achieved.
There are a number of things you can try if you want to achieve a dreamy look, most of them in post-processing.
You might want to use a large aperture to throw the background out of focus and get nice bokeh
In post processing, try increasing contrast and saturation to mimic the look of some film stock like Velvia. Also try adding some grain.
Next you might want to add "glow" to the image : Adding Glow in Photoshop. This is what I expect you might mean by the dreamy look.
An easy way to experiment with the look of old films is using this online emulator and if you are interested in the technology behind it, parts of the source code seem available (make sure to read the license carefully, though, it's not "free" software).
The whole thing is based on color lookup-tables, see also Pat David's blog: