The most important part of a great photo is a great exposure.

When your sensor absorbs the right amount of light, everything gets better: the color, the contrast, and especially the noise — that grainy, blurring effect you see on photos shot in dark rooms.

But what can you do when you under-expose an image, and it turns out too dark?

Snapseed, Photoshop Express, and other photo editing apps offer "enhance" buttons, but they tend to produce ugly, grainy fixes. Adobe Photoshop on a computer does a better job with its "Auto" tools, but most of us don't pay that hefty monthly subscription.

The best way to do it for most people is manually — inside your favorite app.

The amount of light you can rescue from your photo depends on your camera's dynamic range (the amount of detail it captures in shadows and highlights) and the quality of your JPEG file. For this tutorial I used a very dark photo from a high dynamic range camera to exaggerate the effect.

This image comes from a PigPen Theatre Co. concert. The band wandered away from the bright lights of the stage and into the dark of the audience and I didn't adjust in time. I'll use the free Photoshop Express app to spruce it up (more on that app's features here), but you should be able to accomplish something similar in whichever app you prefer.

Here's how the original JPEG for this demo looks.

In Photoshop Express, bump up the exposure/brightness slider, but not too far. This is a blunt instrument, and can wreck your image with grain if overused.

Next, push up the highlight slider. This lightens only the brightest and least grainy parts of your shot.

Now lower the contrast. This takes the jagged edges off the brightness effect, and improves the look of your midtones.

Many dark shots have color issues. Adjust the color as necessary, starting with the temperature. This image was a little too warm so I slid the slider to the cool side.

Tint comes next in the color fix. I shifted the slider a little green-ward here. The other direction is pink.

Usually your image will benefit from a vibrance boost at this point. But don't go overboard.

Noise lives in the shadows, especially in brightened shots. Shifting your shadow slider to the dark side helps, and adds a soft contrast to your image.

I also bumped up the noise reduction a tiny bit here. But this effect can easily make your image look plastic-y and blurry if you go too far.

If your midtones look a little flat and hazy, play with the defog slider until they improve.

Here's how the final edit looked when I exported it.

Here are the takeaways:

When brightening an image, it's easy to overdo it. It's tempting to turn on every effect at maximum, but this can look unnatural.

Noise is your enemy. But the best way to fight it is by nailing your shadow and highlight adjustments, not with the noise reduction tool.

I didn't touch some of the more dramatic effects, like the clarity slider or filters, at all.

Your goal shouldn't be to make the image look like it was shot on a bright day. The closer you stay to how the scene actually looked, the better your result will be.