How to Open the Levels Dialog in Paint.NET
Launch Paint.NET and open a photo that you feel lacks contrast, then go to Adjustments > Levels to open the Levels dialog. Even if you’re used to making levels adjustments in other image-editing software, this dialog may appear a little intimidating at first sight with its two histograms. When adjusting for contrast, there are two features that you should focus on: the Input sliders (on the left) and the Output Histogram (on the right).
How to Adjust the Input and Output Levels Sliders in Paint.NET
Adjusting the Input sliders will change the Output Histogram. As you do so, you’ll see the changes to the image take affect in real time. If the image was underexposed, the histograms are central with empty space above (the light end) and below (the dark end). To improve the appearance of the image, stretch the Output Histogram so that there is almost no space above or below it. To accomplish this: In most cases, you’ll only want to adjust the middle Output slider, but sometimes the top slider can help a photo if used carefully. For example, let’s say you’ve taken a photo with lots of contrast and a few small areas burned out to pure white, such as bright patches in a sky of storm clouds. In that case, you could drag the top slider down a little to add a slight gray tone to those areas. However, if the white areas are large, this can make the photo look flat, so be cautious.
