Sunlight -- don't leave home without it.
For an example of what lighting a diorama with sunlight can do, take a look at the cover of the December Model Railroad Hobbyist. Ken Patternson moves portions of his basement layout outdoors into his back yard and uses the Mississippi River for a distant background. If the shadows are too stark he uses bounce cards to add in some fill lighting.
Nothing looks more realistic than real sunlight. But here are a few suggestions for when real sun light isn't practical.
Approximating this indoors requires:
If you want to take photos that look "real" here are some hints and tips...
o a good balance between a single direct light to simulate the sun and a very diffuse sky bowl light. The direct sunlight should be redder than the skybowl. For example, use a halogen for the direct light and 4100K fluorescents (with at least at CRI of 85). Set the camera to about 3200K white balance for daytime or 3000K for a redder late afternoon effect. Experiment like crazy to balance the amount of indirect and direct light and the white balance of the camera.
o the primary direct (sun) light needs to be far enough away that it is "small" relative to the scene in the way that the sun appears to be "small" to us. Primary light rays should be at least somewhat close to parallel. This says that a large diameter lamp will need to further away. Keeping the light further away also has the benefity of reducing light fall-off from the nearest part of the scene to the furthest. If you light a 4' deep scene with a lamp that's 2' from the nearest part of the scene, the furthest part of the scene is now 3 times further away. The intensity of lighting falls off rapidly as distance increases. A light that is too close will result in very amorphous, poorly defined shadows. Real shadows, tend to be pretty well defined (unless the object casting the shadow is far away from from the shadowed surface.
o white balance -- I already mentioned this. I'm mentioning it again. The best way to accurately white balance a digital camera is to shoot a photo of a neutral gray card and let the camera figure out what red, green, and blue, compensation is needed to make it really white. Using auto-white balance usually doesn't work terribly well. Using the builtin incandescent white balance usually results in a reddish/yellow photo. It's better to get the white balance right in the camera rather than postprocessing color balance with software (such as photoshop).
o don't use too much fill light. Shadows should be dark. Inky black shadows may be too dark (and even the best digital cameras don't have the dynamic range to register bright highlights and still show detail in the dark areas.). If the shadows are too dark, try adding *little* bit more fill light. It's easy to get too much fill lighting -- when that happens all the shadow ares start looking really unnatural -- a bit like a 93 year old super model with too many face lifts and too much makeup.
o most modern digitral cameras do pretty well in low light. This is especially true for DSLRs. You don't need to have enough photo lights turned on to make you squint in the brilliance. Many a great photo has been snapped with lighting that feels really dim. The key is often to make the lighting feel "delicate" rather that blast the subject into submission with a salvo of photon torpedos.
o flash lighting is a whole different ball game. I'd recommend not getting into it unless you're prepared to spend some $$ to get a primary (direct) speedlight and at least one, additional diffuse (bounce) light. Getting a bounce, slave strobe with a stand and umbrella diffuser is probably a good idea. Think the kind of equipment a photo studio uses to take family portraits.
The above is mostly aimed at taking "art" style photos. If you're shooting snap-shots for a photo album or are taking "product" photos, much of the above can be ignored.
Cheers,
Charlie
