Category: Photography Basics > 8. Digital Post-Processing Article ID: 8.4 Created: May 2026

The essentials at a glance

• Brightness determines how light or dark the overall image appears – it is best corrected using gamma/exposure, not a basic brightness slider
• Contrast describes the difference between light and dark areas – too little looks flat, while too much loses detail
• The histogram shows the brightness distribution and is the most reliable tool for assessing exposure

Explanation

Correcting brightness

Basic brightness slider: Raises or lowers all tones evenly → colors quickly become washed out (when brightening) or black (when darkening) → loss of contrast. Suitable only for rough corrections.

Gamma correction (exposure slider in Lightroom): Primarily raises the midtones without significantly shifting the highlights and shadows → contrast is largely preserved. Preferred method for exposure corrections.

Tone curve (gradation curve): Maximum control – each tonal range (shadows, midtones, highlights) can be adjusted independently. Steeper learning curve, more precise results.

Adjusting contrast

Contrast slider: Raises light tones and lowers dark tones simultaneously → S-curve. Quick and effective for images that look flat.

Tone curve: Allows S-curves with precise control over each range. Professional method.

Clarity: Increases local contrast along edges → adds texture and an impression of sharpness. Good for landscapes and architecture; use sparingly for portraits (unflattering for skin).

Adjusting shadows and highlights separately

Modern RAW programs (Lightroom, Darktable) allow separate adjustments:

• Highlights: Darken overexposed areas
• Shadows: Brighten underexposed dark areas
• Whites: Maximum white point
• Blacks: Minimum black point

This allows the image’s dynamic range to be used optimally – details in highlights and shadows are visible at the same time.

Reading the histogram correctly

The histogram shows how many pixels have each brightness level:

• Left: Dark tones (black)
• Right: Light tones (white)
• Clipping on the left (the graph touches the left edge): Shadows are blocked up → shadow areas without detail
• Clipping on the right (the graph touches the right edge): Highlights are blown out → bright areas without detail

Ideal histogram: No clipping at either edge, with the distribution depending on the subject (bright subjects have more values on the right, dark subjects more on the left).

Practical tip

In Lightroom, enable the “Blown Highlights/Blocked Shadows” warning function (J key in the Develop module): Blown highlights are marked in red, and blocked shadows in blue. This lets you immediately see where detail loss is occurring and make targeted adjustments using the highlights and shadows sliders.