Why does the Nikon D3100 not show a live review of my photo before I take it?

Alright, so my girlfriend got a new camera today, it's a Nikon D3100, and even though I own a Canon, I thought I'd help her learn how to use it. I've shown her everything, except when we try to take a photo in manual mode in the live view (LCD screen) the image won't change when you raise or lower the shutter or apperture. Or anything really.

It basically just won't change what the image looks like on-screen no matter what settings you change. The only way you know what the image will look like is if you actually take a photo.

My question: How do you fix this? The canon does this automatically.

Actually it's called Live View and I don't believe your camera has it. Besides dslr cameras are designed with a view finder, I'd advise you learn to use it.

The d3100 does have live view.

i don't have one, but your camera may idle until you wake it up by depressing the shutter release half way to RE-FOCUS, so its also controlled if you like by the FOCUS MODE that is currently dominant.
The focus mode will subsequently be affected by the SHOOTING MODE.

the link below makes a statement that live view is available with NEW AF MODES.

nikon's can be annoying at times and definitely take longer to fathom out their little quirks.

is recommend you get one of the field guides as they usually point out these features.
do an inet search for Nikon D3100 Field Guide

Your question negates itself. You can't review something that has not been taken yet.

I learned photography by myself with a film SLR and it has always been that way even before the dawn of digital photography. You only get to see the effects of your settings after you take the shot. I have never used a Canon dSLR but if they show the effect of each setting change instantly in LiveView mode then there's no need to study photography anymore. Wow! Technology has surely gone too far already.

You are talking about live view, most professional photographers use the viewfinder to compose pictures and only noobs use the live view to switch to live view on the d3100, you see the lever around the red button u pull it and it will switch to live view.

Nikon maintains live view brightness regardless of aperture setting as it is easier to compose a photo when you are seeing everything.

Same thing with the optical viewfinder - it's brightness does not change when you change the aperture either, unless you depress the depth-of-field preview button. And your Canon should work that way as well in the viewfinder at least.

In the SLR days, only the cheapest of SLRs dimmed the viewfinder when you changed aperture, as they lacked any method of stopping down the aperture when the photo was taken. Photographers demanded full brightness when looking through the viewfinder no matter what the aperture setting was as it was all but impossible to see through the viewfinder at small apertures to focus or compose the photo.

Unless you have in incredibly cheap lens, the aperture will remain fully open (for the maximum light input) until you take a photo. As you take the photo, the aperture closes down to whatever you set it to, and immediately returns to wide open after the photo.

Nikon and Canon cameras both do this when you are using the viewfinder. If your Canon does not do this - it's either broken, you have a cheap lens, or you are permanently in DoF preview mode.

In live view mode, Nikon continues to use this design concept it so that you can focus and compose the photo properly. The LCD display is just too small for you to tell if the photo is exposed properly, and it is more accurate to rely on your metering system than guessing the exposure in live view. A dimming live view mode is a crutch you should learn to avoid as it enforces bad habits.

Besides, you should never use live view unless you are doing video. Doing so results in holding the camera incorrectly, which results in more camera shake, which results in blurry photos. The only exception is if you are using the camera on a tripod.

While I can do that with my Nikon D90, I don't see how to do it in the D3100 manual.