DTF Glossary
Alpha channel
An alpha channel stores per-pixel opacity separately from colour. In a typical 8-bit image, 0 means fully transparent, 255 means fully opaque, and values between them create soft edges, shadows, smoke, or residue. DTF prepress can use alpha to define visible artwork and derive an initial white-underbase mask.
In practice
Alpha is not a white-ink plane. It describes how colour is composited; a prepress tool or RIP may interpret that opacity to build white, but the resulting production plane has its own threshold, choke, amount, name, and polarity.
Inspect alpha over several contrasting backgrounds. A checkerboard can hide isolated low-opacity pixels, while a hard cleanup can destroy intentional antialiasing or fades. Approve the colour edge and its derived white together.