The DTF prepress vocabulary

• 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.

• Alpha threshold

  An alpha threshold is the cutoff that separates pixels included in an opacity-derived mask from pixels excluded from it. On an 8-bit alpha scale, changing the cutoff decides whether faint edge or background pixels become white, varnish, visible content, or nothing. It does not repair the underlying colour artwork.

• Anti-aliasing

  Anti-aliasing smooths a raster edge by assigning intermediate colour or opacity to boundary pixels instead of forcing every pixel fully on or off. It reduces visible stair-stepping, but in DTF those semi-transparent edge pixels also affect artwork bounds and the white mask, so they must be inspected rather than deleted automatically.

• Artwork bounds

  Artwork bounds are the smallest declared rectangle used to size and place an item. They may follow visible or thresholded pixels rather than the original canvas. Oversized transparent padding or remote low-alpha debris enlarges the rectangle, which can waste space even when the main design looks tightly cropped.

• BigTIFF

  BigTIFF is a TIFF extension that replaces ClassicTIFF’s 32-bit file offsets with 64-bit offsets so the container can address larger data structures. It solves an offset boundary, not every large-file problem: decoded raster memory, pixel dimensions, channel count, application limits, and RIP support remain separate constraints.

• Channel polarity

  Channel polarity defines which numeric value means more ink or coating in a production plane. One workflow may treat black or 0 as maximum white ink, while another treats white or 255 as maximum coverage. A correct channel name with reversed polarity can produce the opposite mask, so bytes and mapping must be verified.

• Choke (white underbase)

  Choke shrinks the white underbase a small amount relative to the colour art, so the white layer hides just inside colour edges instead of peeking past them as a pale halo when press registration drifts. It is the opposite of spread, which grows the white outward.

• CMYK

  CMYK is a subtractive colour model with cyan, magenta, yellow, and black process channels. The numbers are meaningful only within a colour-management and printing condition; the same CMYK values can render differently through another profile, RIP, ink set, media, or linearisation. CMYK channels do not automatically include a DTF white plane.

• Colour knockout

  A colour knockout removes or makes transparent pixels selected by colour criteria so a background or unwanted region does not print. It is distinct from alpha-threshold cleanup, which selects by opacity, and from white-underbase choke, which erodes a production mask. Tolerance and edge handling determine what the knockout preserves.

• Colour management

  Colour management is the controlled interpretation and conversion of colour numbers between sources, working spaces, proofing conditions, and output devices. It uses profiles and declared conversion rules to preserve a chosen appearance as far as the device gamut permits. It is a workflow, not a promise that one embedded ICC tag makes every application agree.

• Dithering

  Dithering approximates intermediate tone values with patterns or distributions of discrete dots. Ordered dithering repeats a threshold matrix; error-diffusion methods pass quantisation error to neighbouring pixels; stochastic methods distribute dots probabilistically. The visible result depends on raster density, dot geometry, scale, substrate, ink, and the physical process.

• DTF (direct-to-film)

  DTF, or direct-to-film, is a transfer-printing workflow in which artwork is printed onto carrier film, commonly with colour and a white underbase, combined with adhesive powder, cured, and later heat-transferred to a substrate. Prepress prepares size, transparency, layout, white, and the file contract before the RIP drives the printer.

• Film utilisation

  Film utilisation is the share of a produced sheet’s area assigned to the declared item area under a stated measurement method. A common rectangular-bounds formula is total reserved item area divided by roll width times used length. It is method-dependent: bounds, gap, margin, marks, and unplaced items must be disclosed.

• Gang sheet

  A gang sheet is a single print-ready file that packs many separate designs onto one run of DTF film, so they print in one pass instead of one file per design. Shops gang orders together to cut film waste and printer time; the packing quality decides how much film one sheet saves.

• Gap (gang-sheet spacing)

  Gap is the minimum spacing a layout reserves between neighbouring item rectangles on a gang sheet. It is not the same as outer sheet margin, visible-art clearance, or a cutter’s required lane. A smaller gap relaxes packing geometry, but only a finishing test can show whether the resulting pieces remain separable and repeatable.

• Halftone

  A halftone represents continuous tone with discrete printed dots whose size, spacing, or distribution changes the perceived density. In DTF, halftoning may be applied to visible artwork or to the white underbase. Those uses have different goals and must be evaluated at final scale through the actual RIP and physical output.

• ICC profile

  An ICC profile describes how device or colour-space numbers relate to a standard colour reference. A source profile helps interpret incoming RGB or CMYK values; an output profile characterises an intended printing condition. Embedding, assigning, converting with, and merely detecting a profile are different operations and must not be described as interchangeable.

• LPI (lines per inch)

  LPI is a halftone frequency: the number of screen cells or nominal lines per inch. In a raster implementation, cell size is derived from image pixels per inch divided by LPI. Higher LPI creates smaller cells at the same raster density, but does not guarantee more usable detail through a given printer and material process.

• Mirror (image reversal)

  Mirroring reverses the output horizontally so a transfer reads in the intended orientation after it is applied. Whether reversal belongs in artwork, prepress, the export recipe, or the RIP is a workflow decision. Applying it twice cancels it; applying it nowhere can make text and directional graphics print backwards.

• Nesting

  Nesting is the placement of many items inside a sheet or roll boundary while respecting dimensions, gap, margin, and allowed rotation. Its objective may be shorter used length, lower film area, fewer sheets, or easier finishing. A dense-looking layout is not proof of a global optimum or of production-safe clearances.

• PPI vs DPI

  PPI describes image pixels per printed inch; printer DPI describes device-addressable dots or drops per inch. They are related only through a production process, not interchangeable labels. Effective image PPI equals the source pixel dimension divided by intended physical inches, while printer DPI belongs to the downstream device and RIP configuration.

• Preflight

  Preflight is the structured check performed before release to find file and layout conditions that may make output wrong: physical size, effective resolution, alpha, colour metadata, artwork bounds, overlaps, off-sheet placement, white source, spots, mirror state, and RIP handoff. A finding is evidence for review, not automatic customer approval.

• PSD and PSB

  PSD is Adobe Photoshop’s version-1 document format; PSB is the large-document version-2 format. Adobe’s specification sets a 30,000-pixel-per-dimension boundary for PSD and 300,000 for PSB. Either can carry extra spot channels, but the extension does not prove a RIP accepts the file or preserves its production mapping.

• Resampling

  Resampling changes an image’s pixel dimensions by removing pixels or calculating new ones. It differs from changing resolution metadata, which can alter interpreted physical size without changing the grid. Upsampling may smooth an enlargement but cannot reconstruct fine detail, edge information, or type clarity that the source never contained.

• RGB

  RGB is an additive colour model that describes colour with red, green, and blue components. It is a practical interchange space for artwork with transparency, but RGB numbers are not printer ink recipes. A profile and conversion path determine their meaning, while the RIP and device condition determine how printable inks reproduce them.

• RIP (raster image processor)

  A RIP converts page or image data into device-ready rasters and controls output responsibilities such as separations, screening, colour conversion, ink channels, media modes, queues, and printer communication. Capabilities vary by product and version. Prepress prepares a validated handoff; it does not replace the RIP’s device-control role.

• RIP preset

  A RIP preset is a saved handoff recipe that groups choices such as container, colour model, ICC profile, alpha handling, spot counts and names, mirror state, and other export defaults for a target workflow. It reduces repeated setup, but it proves only the file writer’s configuration—not acceptance by every RIP version or queue.

• Roll width

  Roll width is the nominal cross-web width of continuous print media. It is not automatically the same as loaded, imageable, or packed usable width; printer limits, tracking, edge exclusions, marks, handling, and outer margin can reduce the production region. Compare widths using total film area, not sheet length alone.

• Rotation (nesting)

  Rotation turns an item to another allowed orientation so its rectangular bounds may fit a sheet more efficiently. DTF gang-sheet packers commonly test 0° and 90°, but geometric permission is not semantic approval. Text direction, artwork intent, labels, grain, marks, cutting, or customer instructions may require a fixed orientation.

• Screen angle

  Screen angle is the orientation of a halftone grid or dot structure relative to the image axes. Changing it rotates the pattern without changing nominal LPI. Angle can affect visible texture and moiré when the artwork screen interacts with raster sampling, another screen, fabric structure, or downstream RIP processing.

• Sheet margin

  Sheet margin is the reserved border between the outermost packed item bounds and the selected sheet edge. It protects a layout boundary, but it does not automatically equal a printer’s non-imageable region, a registration-mark zone, roller clearance, handling allowance, or visible-art distance. Those downstream constraints must be checked separately.

• Soft-hand underbase

  A soft-hand underbase reduces solid white coverage with a controlled pattern so the transferred area can feel less heavy than a fully solid backing. It trades coverage structure against colour support and durability. The result depends on dot method, density, artwork, fabric, ink, powder, cure, press, and wash testing.

• Spot channel

  A spot channel is a separate raster plane assigned to a named production ink, coating, or operation rather than mixed into process RGB or CMYK colour. DTF workflows use spots for white; UV-related handoffs may also use varnish. The plane’s bytes, name, order, and polarity must match the receiving workflow.

• TIFF

  TIFF is a tag-based raster container that can represent several colour models, bit depths, compression schemes, metadata fields, alpha, and additional planes. “TIFF” therefore does not identify one production structure. A DTF handoff must declare dimensions, density, primary colour, channel count, spot names, polarity, compression, and reader compatibility.

• Transparency

  Transparency means pixels can be partially or fully absent from the visible composite, usually through an alpha channel. A transparent-looking editor background does not prove the exported file contains alpha, and alpha does not prove the edge is clean. Low-opacity residue, padding, and intentional fades require separate inspection.

• UV-DTF

  UV-DTF is a transfer workflow for adhesive decals in which UV-cured colour, white, and commonly varnish are built on a film system and transferred to a hard surface. Its ink, film, lamination or transfer, curing, and spot-layer requirements differ from garment DTF, so the two workflows should not share unverified settings.

• Varnish channel

  A varnish channel is a separate grayscale production plane that tells a UV-capable workflow where to place clear coating. It is not process colour, transparency, or white underbase. Its coverage, name, polarity, and optional outward spread must be validated against the exact RIP, printer, ink, film, curing, and transfer process.

• W1 channel

  W1 is a conventional name for the first white-ink spot plane in some DTF file and RIP workflows. It is a label, not a universal standard or guarantee of mapping. The receiving queue must still discover the plane, interpret its polarity, assign it to white ink, and preserve registration with colour.

• White halo

  A white halo is visible white ink extending beyond the intended colour edge of a transfer. It can come from underbase geometry that is too large, colour-to-white registration offset, scaling or mapping errors, or low-opacity colour residue that changes the derived mask. The symptom must be classified before choke is adjusted.

• White underbase

  A white underbase is a production ink plane printed beneath colour so the substrate does not show through and weaken the intended appearance. In DTF it is commonly derived from artwork alpha, then adjusted with threshold, choke, amount, soft-hand patterning, or halftone. It is separate from the colour composite.

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