{"course":{"slug":"vector-and-print","title":"Vectors, Logos and Things That Get Printed","url":"https://addaly.com/learn/vector-and-print","level":"beginner","track":"create"},"lesson":{"slug":"where-vector-becomes-pixels","title":"Where vector quietly becomes pixels","url":"https://addaly.com/learn/vector-and-print/where-vector-becomes-pixels","position":7,"of":73,"minutes":10,"answer":"Shadows, blurs, meshes and blend modes are generated as pixels at a resolution the document sets (often 72 ppi by default) and anything transparent gets sliced into atomic regions when flattened.","keyIdea":"Shadows, blurs, meshes and blend modes are generated as pixels at a resolution the document sets (often 72 ppi by default) and anything transparent gets sliced into atomic regions when flattened, which is where the grey box and the hairline seam come from."},"body":{"format":"markdown","text":"## The effects that are not vector at all\n\nSome things in a vector application are geometry. Some are pictures generated on the fly. The second group has a resolution, and if you do not set it, the software picks one for you, often badly.\n\nRaster by nature, in every program:\n\n- Drop shadow, outer glow, inner glow\n- Gaussian blur and feather\n- Most texture, grain and distortion filters\n- **Gradient mesh** (Illustrator) and mesh fills (Inkscape, CorelDRAW)\n- Anything under Illustrator's Effect ▸ Photoshop menu\n\nCompositing, which is not raster but needs flattening in older workflows:\n\n- Any object below 100% opacity\n- Blend modes: multiply, screen, overlay, soft light\n- Transparency inside a placed PDF or PSD\n\n## The 72 ppi trap\n\nIllustrator has a document setting called **Raster Effects Resolution**. For years the default on a new document was *Screen (72 ppi)*. Every drop shadow, every feather, every blur in that document is generated at 72 ppi.\n\nYou will not see it. On screen at 100% it looks perfect, because your screen is roughly 72 to 110 ppi. It prints as a visibly chunky, stepped shadow.\n\nFix it on day one: Effect ▸ Document Raster Effects Settings ▸ **300 ppi** for print, and check it again whenever you open somebody else's file. Inkscape's equivalent is in Document Properties (default export dpi and filter quality); CorelDRAW sets it per-effect in the bitmap resolution dropdown.\n\n## What flattening actually does\n\nA press workflow that cannot handle live transparency (PDF/X-1a, EPS, PostScript, older RIPs) must **flatten** it. The flattener does something surprising:\n\n1. It finds every region where a transparent object overlaps something.\n2. It divides the artwork into *atomic regions*: areas that can each be described with a single opaque appearance.\n3. Regions that can be expressed as vectors stay vector. Regions that cannot (because a gradient is blending through a blur, say) are rasterised at the flattener's chosen resolution.\n4. It reassembles the page from those pieces.\n\nTwo well-known artefacts come straight out of step 3 and 4.\n\n**The grey or white box behind a logo.** The rasterised region is rectangular, it carries the background it was composited against, and if the background in the file is not the background on the paper, the rectangle shows.\n\n**The hairline seam.** Two adjacent atomic regions share an edge. One is drawn as vector, one as a raster tile. Their anti-aliasing does not agree exactly along that edge, so a light line one pixel wide appears across your artwork: visible on screen at some zoom levels and, worse, sometimes on the printed sheet.\n\nIllustrator's **Flattener Preview** panel (Window ▸ Flattener Preview) shows you which regions will rasterise before you export. Acrobat Pro's Output Preview has a transparency flattening view. Both are worth a look before a big job.\n\n## How to avoid the whole problem\n\n- **Export PDF/X-4 where the shop can take it.** X-4 keeps transparency live all the way to the RIP, which does the flattening once with full knowledge of the device. No atomic regions in your file, no seams.\n- **Ask.** \"Do you want X-1a or X-4?\" is one line in an email and it settles this.\n- **Build flat where you can.** A shadow made from a solid shape at a lower tint is not transparency and never flattens. A \"gradient\" built as five flat steps in a screen-printed job is a deliberate decision, not a limitation.\n- **Rasterise on purpose.** If an element needs a blur, rasterise it yourself at 300 ppi with a known background, and place it. You now control the resolution and the edge rather than discovering them later.\n\n## The limitation\n\nResolution independence is a property of *geometry*, not of the file extension. An `.ai` file whose hero image is a gradient mesh with a Gaussian blur over it is, for practical purposes, a raster file in a vector wrapper. It will not enlarge cleanly and it will choke a plotter.\n\nThe test is not what the file is called. It is what is inside: select everything, look at the Document Info or Objects panel, and see whether the count is paths or effects."},"check":{"question":"A logo with a soft drop shadow is exported as PDF/X-1a. On press, a faint rectangle of slightly different white appears around the mark, and a thin light line runs across the shadow. What produced these two artefacts?","options":[{"text":"The shadow was drawn at 72 ppi, so it was upsampled by the press RIP, and the interpolation produced both the rectangle and the line running across it.","correct":false,"tempting":"A low raster-effects resolution produces a visibly stepped, chunky shadow. It does not create a rectangular boundary or a seam, which are geometry, not sampling."},{"text":"PDF/X-1a converts RGB to CMYK, and the shadow's alpha channel was converted into a light grey fill.","correct":false,"tempting":"Colour conversion changes hue and density uniformly; it cannot produce an edge at a rectangle boundary that has nothing to do with the artwork's shape."},{"text":"The flattener sliced the page into atomic regions, rasterised those containing the shadow, and left mismatched edges between them.","correct":true},{"text":"The press used a coarser line screen than the proof, so the shadow's halftone dots grouped into visible bands.","correct":false,"tempting":"Coarser screening shows as dot pattern across the whole tonal area, not as a rectangular boundary and a single straight seam."}]},"prev":{"slug":"clipping-hides-it-does-not-remove-it","title":"Clipping hides; it does not remove","url":"https://addaly.com/learn/vector-and-print/clipping-hides-it-does-not-remove-it"},"next":{"slug":"tracing-and-when-to-redraw","title":"What auto-trace is doing, and when to redraw instead","url":"https://addaly.com/learn/vector-and-print/tracing-and-when-to-redraw"},"authorship":"Founder and series editor: Dr Mustafa Mun. Written by AI models to a written standard. Exam keys checked blind by a second model: 3,665 of 3,666 agreed. Academic review invited.","review":{"status":"Draft, open for academic review"},"cite":"Addaly (2026) 'Where vector quietly becomes pixels', in Vectors, Logos and Things That Get Printed. Edited by M. Mun. Addaly. Available at: https://addaly.com/learn/vector-and-print/where-vector-becomes-pixels (Accessed: 13 October 2026).","licence":{"name":"CC BY-NC-SA 4.0","url":"https://creativecommons.org/licenses/by-nc-sa/4.0/"},"reader":{"schema":1,"title":"Where vector quietly becomes pixels","courseTitle":"Vectors, Logos and Things That Get Printed","module":{"index":1,"slug":"what-a-vector-is","title":"The thing that is actually in the file"},"answer":null,"keyIdea":"Shadows, blurs, meshes and blend modes are generated as pixels at a resolution the document sets (often 72 ppi by default) and anything transparent gets sliced into atomic regions when flattened, which is where the grey box and the hairline seam come from.","hero":{"kind":"plate","image":null,"alt":null,"caption":null},"blocks":[{"t":"h2","id":"the-effects-that-are-not-vector-at-all","runs":[{"text":"The effects that are not vector at all"}]},{"t":"p","runs":[{"text":"Some things in a vector application are geometry. Some are pictures generated on the fly. The second group has a resolution, and if you do not set it, the software picks one for you, often badly."}]},{"t":"p","runs":[{"text":"Raster by nature, in every program:"}]},{"t":"ul","items":[[{"text":"Drop shadow, outer glow, inner glow"}],[{"text":"Gaussian blur and feather"}],[{"text":"Most texture, grain and distortion filters"}],[{"text":"Gradient mesh","b":true},{"text":" (Illustrator) and mesh fills (Inkscape, CorelDRAW)"}],[{"text":"Anything under Illustrator’s Effect ▸ Photoshop menu"}]]},{"t":"p","runs":[{"text":"Compositing, which is not raster but needs flattening in older workflows:"}]},{"t":"ul","items":[[{"text":"Any object below 100% opacity"}],[{"text":"Blend modes: multiply, screen, overlay, soft light"}],[{"text":"Transparency inside a placed PDF or PSD"}]]},{"t":"h2","id":"the-72-ppi-trap","runs":[{"text":"The 72 ppi trap"}]},{"t":"p","runs":[{"text":"Illustrator has a document setting called "},{"text":"Raster Effects Resolution","b":true},{"text":". For years the default on a new document was "},{"text":"Screen (72 ppi)","i":true},{"text":". Every drop shadow, every feather, every blur in that document is generated at 72 ppi."}]},{"t":"p","runs":[{"text":"You will not see it. On screen at 100% it looks perfect, because your screen is roughly 72 to 110 ppi. It prints as a visibly chunky, stepped shadow."}]},{"t":"p","runs":[{"text":"Fix it on day one: Effect ▸ Document Raster Effects Settings ▸ "},{"text":"300 ppi","b":true},{"text":" for print, and check it again whenever you open somebody else’s file. Inkscape’s equivalent is in Document Properties (default export dpi and filter quality); CorelDRAW sets it per-effect in the bitmap resolution dropdown."}]},{"t":"h2","id":"what-flattening-actually-does","runs":[{"text":"What flattening actually does"}]},{"t":"p","runs":[{"text":"A press workflow that cannot handle live transparency (PDF/X-1a, EPS, PostScript, older RIPs) must "},{"text":"flatten","b":true},{"text":" it. The flattener does something surprising:"}]},{"t":"ol","start":1,"items":[[{"text":"It finds every region where a transparent object overlaps something."}],[{"text":"It divides the artwork into "},{"text":"atomic regions","i":true},{"text":": areas that can each be described with a single opaque appearance."}],[{"text":"Regions that can be expressed as vectors stay vector. Regions that cannot (because a gradient is blending through a blur, say) are rasterised at the flattener’s chosen resolution."}],[{"text":"It reassembles the page from those pieces."}]]},{"t":"p","runs":[{"text":"Two well-known artefacts come straight out of step 3 and 4."}]},{"t":"p","runs":[{"text":"The grey or white box behind a logo.","b":true},{"text":" The rasterised region is rectangular, it carries the background it was composited against, and if the background in the file is not the background on the paper, the rectangle shows."}]},{"t":"p","runs":[{"text":"The hairline seam.","b":true},{"text":" Two adjacent atomic regions share an edge. One is drawn as vector, one as a raster tile. Their anti-aliasing does not agree exactly along that edge, so a light line one pixel wide appears across your artwork: visible on screen at some zoom levels and, worse, sometimes on the printed sheet."}]},{"t":"p","runs":[{"text":"Illustrator’s "},{"text":"Flattener Preview","b":true},{"text":" panel (Window ▸ Flattener Preview) shows you which regions will rasterise before you export. Acrobat Pro’s Output Preview has a transparency flattening view. Both are worth a look before a big job."}]},{"t":"h2","id":"how-to-avoid-the-whole-problem","runs":[{"text":"How to avoid the whole problem"}]},{"t":"ul","items":[[{"text":"Export PDF/X-4 where the shop can take it.","b":true},{"text":" X-4 keeps transparency live all the way to the RIP, which does the flattening once with full knowledge of the device. No atomic regions in your file, no seams."}],[{"text":"Ask.","b":true},{"text":" “Do you want X-1a or X-4?” is one line in an email and it settles this."}],[{"text":"Build flat where you can.","b":true},{"text":" A shadow made from a solid shape at a lower tint is not transparency and never flattens. A “gradient” built as five flat steps in a screen-printed job is a deliberate decision, not a limitation."}],[{"text":"Rasterise on purpose.","b":true},{"text":" If an element needs a blur, rasterise it yourself at 300 ppi with a known background, and place it. You now control the resolution and the edge rather than discovering them later."}]]},{"t":"h2","id":"the-limitation","runs":[{"text":"The limitation"}],"role":"limit"},{"t":"p","runs":[{"text":"Resolution independence is a property of "},{"text":"geometry","i":true},{"text":", not of the file extension. An "},{"text":".ai","code":true},{"text":" file whose hero image is a gradient mesh with a Gaussian blur over it is, for practical purposes, a raster file in a vector wrapper. It will not enlarge cleanly and it will choke a plotter."}]},{"t":"p","runs":[{"text":"The test is not what the file is called. It is what is inside: select everything, look at the Document Info or Objects panel, and see whether the count is paths or effects."}]}],"check":{"question":[{"text":"A logo with a soft drop shadow is exported as PDF/X-1a. On press, a faint rectangle of slightly different white appears around the mark, and a thin light line runs across the shadow. What produced these two artefacts?"}],"options":[{"text":[{"text":"The shadow was drawn at 72 ppi, so it was upsampled by the press RIP, and the interpolation produced both the rectangle and the line running across it."}],"correct":false,"tempting":[{"text":"A low raster-effects resolution produces a visibly stepped, chunky shadow. It does not create a rectangular boundary or a seam, which are geometry, not sampling."}]},{"text":[{"text":"PDF/X-1a converts RGB to CMYK, and the shadow’s alpha channel was converted into a light grey fill."}],"correct":false,"tempting":[{"text":"Colour conversion changes hue and density uniformly; it cannot produce an edge at a rectangle boundary that has nothing to do with the artwork’s shape."}]},{"text":[{"text":"The flattener sliced the page into atomic regions, rasterised those containing the shadow, and left mismatched edges between them."}],"correct":true,"tempting":null},{"text":[{"text":"The press used a coarser line screen than the proof, so the shadow’s halftone dots grouped into visible bands."}],"correct":false,"tempting":[{"text":"Coarser screening shows as dot pattern across the whole tonal area, not as a rectangular boundary and a single straight seam."}]}],"order":[1,3,2,0],"why":null},"prev":{"slug":"clipping-hides-it-does-not-remove-it","title":"Clipping hides; it does not remove","minutes":8},"next":{"slug":"tracing-and-when-to-redraw","title":"What auto-trace is doing, and when to redraw instead","minutes":9}}}