What are the biases in day and nighttime landscape auto modes in terms of aperture, iso and shutter speeds?
In any landscape mode, ideally you want small aperture for depth of field, low ISO and you assume a static scene so shutter speed isn't important, and in fact a tripod may be assumed.
Daytime Landscape should give preference to smaller apertures for greater depth of field, e.g. f/8 or f/11. ISO and shutter speed would be managed to get the lowest ISO possible without having too slow a shutter speed. Some cameras might allow the shutter speed to get below the level at which you could hand hold (and assume you use a tripod). Others might raise the ISO if it keeps the shot in hand-held range.
Night Landscape will probably vary a lot between cameras. The main thing is that by putting the camera in Night Landscape mode, the camera knows you are photographing a long-range scene, so popping up the flash is not going to work. There are then two options, which again may vary:
- Raise ISO, widen aperture in order to try to get a decent hand-held exposure
- Assume camera is on a tripod or table top, and keep ISO low to keep noise down, keep aperture small for depth of field, and increase the shutter to several seconds if necessary to get the exposure.
Most cameras will disable the flash in Night Landscape mode. They will often have a Night Portrait mode which will use slow-sync (rear-curtain) flash to illuminate a nearby subject.
On a compact like a Nikon Coolpix, Night Landscape itself has two sub-modes:
Hand-held - this fires off a number of shots, and then merges them in-camera to try to get one shake-free exposure. I would imagine the shutter speed would be on the order of 1/15th, something like that.
Tripod - choosing this sub-mode lets the camera know it's on a tripod, so it does one long exposure, which may be several seconds.
On a DSLR like the D7000, Night Landscape will assume you have a tripod, or have the camera steadied against something. It will keep the ISO low (Auto-ISO disabled) and allow a long exposure.
I would expect that since Night Scenes are dark, the Night Landscape mode ought to dial in some negative exposure compensation so that the image is somewhat dark, rather than trying to render a daytime scene. I don't use scene modes, so I'm not sure if that's what they do.