Always Make Your Poster File at the Biggest Size You Sell

A customer buys an A5 print. You supply an A5 file. Everyone's happy.

Then the same design sells as A0, and you're stuck. The only file you have is A5, so you enlarge it, send it off, and hope. What arrives is soft — edges slightly furred, fine text mushy, the whole thing looking like a photo of a poster rather than a poster.

The fix costs you nothing at the time and everything once it's too late: master every design at the largest size you're willing to sell, and let each order shrink it down.

Shrinking and enlarging are not opposites

This is the whole idea, and it's worth being precise about why.

When you shrink an image, the software has more information than it needs. Four pixels become one, and it can work out a sensible value for that one from the four it can see. Detail is discarded, but nothing is guessed. The result is genuinely sharp.

When you enlarge an image, the software has less information than it needs. It must produce pixels that never existed, by looking at the neighbours and estimating what should sit between them. That estimate is always a blur, because a smooth average is the safest guess. Edges that were crisp become gradients.

So the two operations are not symmetrical. One throws away data you had. The other manufactures data you never had.

The A5-to-A0 gap is bigger than it sounds

Each step down the A-series halves the area. A5 to A0 is five steps, so A0 is 32 times the area of A5 — not five times.

At 300 DPI:

Blow an A5 file up to A0 and roughly 31 of every 32 pixels in the final file are invented. Nothing in that file was measured; almost all of it was estimated from the 3% that was real.

Put the other way round: an A5-native file printed at A0 works out at about 53 DPI. For context, PSDmate flags anything under 100 DPI as an error before you publish, and warns under 150. Fifty-three is not a borderline case.

Run it the right way round and the maths is boring, which is the point. An A0 master printed at A5 lands at roughly 1700 DPI. The printer discards what it can't use and prints something perfectly sharp.

What "stretched pixels" actually looks like in the post

Nobody returns a poster because its DPI was wrong. They return it because of what they can see:

• Furred edges. Anywhere a dark shape meets a light background, there's a soft transition instead of a clean line.
• Mushy small text. Quotes, dates and captions go first. Thin strokes blur into their own background.
• Flat texture. Grain, paper texture and fine linework average themselves out into a slightly plasticky wash.
• Haloing on AI artwork. Upscaled AI images often gain faint bright rims around high-contrast shapes — the upscaler over-sharpening its own guesses.

None of this is obvious on a phone screen. All of it is obvious on a wall.

Why this costs money, not just quality

A soft print doesn't just cost you that one sale. On Etsy the damage compounds:

1. The refund. You pay the print cost, the shipping, and usually the return.
2. The review. A three-star "nice design, print quality wasn't great" sits on the listing permanently.
3. The ranking. Reviews and order quality feed Etsy's search placement, so a handful of quality complaints quietly costs you impressions on every listing in the shop.
4. The reprints. If the file is the problem rather than the printer, every large order from that design has the same fault waiting in it.

The asymmetry is stark. Mastering large costs you disk space and a slightly slower export. Mastering small costs you the largest, highest-margin orders you'll ever get — because the big sizes are exactly the ones where the flaw shows.

The rule, and the sensible exception

Master at the largest size you'd ever accept an order for. For A-series posters that's A0. Then let each order downsize from that one file.

The exception is DPI, not dimensions. 300 DPI is a comfortable default, but it comes from print work viewed at reading distance. A0 posters are viewed from across a room, and viewing distance scales with size. 150 DPI at A0 is genuinely fine — that's 4967 × 7022 px, about 35 megapixels, and it will look sharp on a wall.

What you must not do is drop the dimensions. A 150 DPI A0 master still downsizes beautifully to A5. A 300 DPI A5 master still can't go up.

If you're working from AI-generated art, generate at the largest size the model supports and upscale once, early, before you build the design around it. Upscaling a finished composition is far worse than upscaling the raw image and then working at full size.

Keeping the file under the limit

A0 at 300 DPI is 139 megapixels, which is an unwieldy file, and PrintShrimp accepts print files up to 50 MB. So:

• Export as JPEG at quality 90–95 for anything photographic or painterly. A 35–70 MP JPEG at that quality typically lands well inside 50 MB, and the compression artefacts are invisible in print.
• Use PNG only when you need transparency or the design is flat vector-style colour, where PNG both compresses better and stays crisp.
• Export sRGB, not CMYK or Adobe RGB. PSDmate warns on anything else because the conversion happens at the printer, and a file already converted twice shifts colour.
• 150 DPI at A0 is the pressure valve. If 300 DPI won't fit under 50 MB, drop the DPI, never the dimensions.

For the full picture on resolution, colour profiles and bleed, see the DPI and resolution guide. For what Etsy itself requires of your listing images — a separate question from your print files — see Etsy image size requirements, and which format to export as for the JPEG-versus-PNG decision in detail.

How PSDmate handles this

When a product has several sizes enabled, PSDmate doesn't send a separate file per size. It picks one master print file — the largest A-series size you've enabled — and that single file backs every variation. Smaller orders are produced from it by downsizing, which is the safe direction.

That's why the size you enable matters. Enable A0 and your A5 orders print from an A0 master. Enable only A5 and every order, including the big ones, is limited by it.

Before you publish, PSDmate checks the effective DPI of your artwork against every size you've switched on, and flags anything under 150 DPI as a warning and under 100 as an error — per size, so you find out that A1 is marginal while you can still do something about it.

The short version

Downsizing keeps quality because it discards information you already had. Upsizing loses quality because it invents information you never had. A5 to A0 means inventing about 97% of the file, and the result lands near 53 DPI.

Build the master once, at the top of the range. Every smaller order comes out of it for free — and the A0 sale, when it arrives, is the one that pays.