Banding

Banding is a digital artifact where a smooth gradient, such as a clear sky or a studio backdrop, breaks into visible steps or stripes instead of blending evenly. It happens when the file has too few tones to describe the gradient, or when a flickering light is caught by a sensor reading the frame row by row. Both cases leave flat strips of one shade next to another, like contour lines on a map.

Tonal banding is a file problem. An 8-bit JPEG has 256 steps per color channel, and a strong edit spreads those steps far enough apart to see. Flicker banding is a shutter problem. LED and fluorescent lamps pulse with mains power, and an electronic shutter reads the frame row by row, so some rows catch a bright phase and others a dark one. Tonal banding follows the gradient; flicker banding is horizontal stripes across the whole frame.

A clear sky is one long gradient with no texture to hide the steps. From deep blue at the top to pale blue near the horizon, it uses only a small slice of the available tones, often 20 or 30 values in an 8-bit file. Any edit that stretches that slice, such as dehaze, a curves move, or a graduated filter, widens the gaps between values until each one becomes a visible stripe. Studio backdrops and vignettes band for the same reason.

It prevents most tonal banding. A 12-bit RAW file holds 4,096 steps per channel and a 14-bit file holds 16,384, compared with 256 in a JPEG. The same edit that bands a JPEG leaves a RAW file smooth. Banding can still appear if the edited image is exported as a low-quality JPEG, or if a heavy gradient is pushed far beyond what the sensor captured. RAW does nothing for flicker banding, which comes from the shutter, not the file.

Start by easing off the edit that caused it, usually dehaze, clarity, or a steep curve. If the steps remain, add a small amount of grain or noise over the affected area. The random texture hides the steps and the eye reads the gradient as smooth. In Photoshop, convert the document to 16 bits per channel before editing gradients, and apply a slight Gaussian blur to the banded area on a separate layer if grain alone is not enough. Export at high JPEG quality.

Many monitors and laptop screens are 6-bit panels that simulate more colors by flickering between two shades. They add steps to gradients that the file does not have. Browsers and photo apps can also band an image while scaling it to fit the window. Check the image at 100 percent zoom and, if possible, on a second display before deciding the file is at fault. A calibrated 8-bit or 10-bit monitor shows what the file holds.

LED and fluorescent lamps pulse 100 or 120 times a second, twice the frequency of mains power. A sensor using an electronic shutter or electronic front curtain reads the frame one row at a time over a fraction of a second, so some rows are exposed during a bright pulse and others during a dim one. The result is horizontal stripes across the frame, sometimes with a color shift. A shutter speed of 1/100 s or 1/120 s covers a full pulse and evens the rows out.

Posterization is banding taken to the extreme. A gradient that should hold hundreds of tones collapses into a few flat patches, so the photo looks like a poster printed with a handful of inks. It happens when a low-bit-depth file is edited hard, saved repeatedly as a JPEG, or run through heavy compression. Some editing apps offer posterization as a deliberate graphic effect, which is the same process applied on purpose.

Yes, in most cases. A light layer of grain or noise adds random variation to each pixel, which scatters the hard edges between steps so the gradient reads as smooth. The technique is called dithering, and printers and screens use it all the time. Add the grain after all other edits and keep it subtle; a grain amount of 10 to 20 in Lightroom is usually enough. It does not fix flicker banding, where the stripes are far too strong to hide.

It can, and often more clearly than on screen, because a large print magnifies a sky gradient and the viewer looks at it longer. Send the printer a 16-bit TIFF instead of a JPEG when the image has wide smooth areas. Soft proof the file before printing and inspect skies and shadows at 100 percent. A printer's own dithering hides small steps, but strong banding in the file survives the trip to paper.