Input and Output Levels
When using ‘Levels’ adjustment layers it is important to note the differences between input and output levels. Input levels allow you to change black levels, white levels and mid-tones. This can be used to add contrast to an image and make the darks darker or lights lighter.
Output levels adjust how dark ‘black’ is in an image and how light ‘white’ is. Using the output levels, it is possible to change the ‘black’ point to grey, giving the image a less contrasted look.
Adjusting Colors using Levels
Levels adjustment layers can also be used to change color in an image. To change colors, click on the color channel drop down – by default it will be on RGB. From here the Red, Green and Blue channels can be adjusted individually.
For instance – to add blue into the shadows of and image, select the ‘Blue’ color channel and slide the dark point to the right on the output levels.
To finish the image and give it that ‘Film’ look, a slight gaussian blur was applied. This makes the image look like it was taken with a lower quality lens. Next noise was added to the image to simulate film grain.