On a digital SLR, you won't see the scene you're about to photograph on the LCD screen—unless you engage Live View.
The scene doesn't automatically appear on the LCD screen like a point-and-shoot camera.
That's because the mirror inside your camera has to flip up so the sensor can send the image to the LCD screen.
When the mirror is flipped up, you can't see through the viewfinder.
The viewfinder isn't as accurate as the LCD screen.
On the LCD screen, the following are more accurate:
You may be able to focus manually, which may be better than autofocus when doing close-ups.
You may be able to enlarge the image on the LCD screen, facilitating focusing.
You may be able to preview depth-of-field.
• Exposure, contrast, and color
As for the color, the LCD screen isn't calibrated.
So the color on it won't be as good as the color on your monitor.
However, LCD-screen color is a far better representation of the color versus the viewfinder.
• The mirror may need to be flipped down quickly for autofocus, slowing it down.
• Sunlight can make the LCD screen hard to see.
• Live View consumes more battery power.
There may be a longer delay between pressing the shutter release and the shutter opening.