Tutorial: Overexposed VS Underexposed

So what's the difference between an overexposed and underexposed photo? The difference is that one is too dark, and one is too bright. Being that in the photo, some details are lost because of the dark or light pixels, which beams out, destroying all that detail.
A lot of people always ask me why I always use flash in my photography. Many people nowadays doesn't need to do this, but I do, because my camera isn't very good at handling high ISO levels, so about 400ISO, it starts being very noisy. If you don't know what I mean by noise, see here. So I tend to use my flash to at least expose it properly, otherwise, I've just a whole bunch of noisy photos to deal with at post processing time.
So lets see what's the difference between the two and how to tell:
This is an underexposed photo. It loses all the details in the dark parts like the shadows. And even to the eye, it's too dark. This is caused by a fast shutter speed, or a small aperture, or a low ISO.

So let's relate that to each one to this photo.
With shutter speed: it's too fast, and didn't get enough time to expose the sensor to the light.
With aperture: it is too small. The opening of the lens is not wide enough to let enough light in.
With ISO: it was too low, and it didn't have enough of them going out to bring the light in.


This is an overexposed photo. It has lost all the details in the bright bits, and basically it's TOO BRIGHT! This will kill your eyes, if it's in the full size.

Shutter speed: It's too slow. It took too much light in, and the shutter speed could be adjusted to be quicker.

Aperture: It's too big, the opening of the lens too every speck of the light and threw it into the sensor. 

ISO: It's too high, it put too much out collecting too much light.

So here's a photo that is nicely exposed. The blacks are not too black, and the whites aren't too white. It's good.

NEXT TUTORIAL:

But having said that overexposing and underexposing is bad, there is ways to edit it, and which one is easier to edit? Keep an eye out for the next coming post!