AI Upscaling for Print: PPI, DPI, and File Size Guide
Print demands more resolution than screens. A photo that looks sharp on your phone can look blurry on a poster. This guide explains what resolution you actually need and how AI upscaling gets you there.
PPI vs DPI: What's the Difference?
PPI (pixels per inch) describes the digital image. A 3000×3000 pixel image printed at 10 inches will have 300 PPI.
DPI (dots per inch) describes the printer. Most professional printers print at 300 DPI. The printer creates one ink dot per pixel at 300 DPI.
The rule: your image PPI should match or exceed the printer DPI. For 300 DPI printing, your image needs at least 300 PPI at the final print size.
How Much Resolution Do You Need?
| Print Size | At 300 PPI | At 150 PPI | Typical Use |
|---|---|---|---|
| 4×6 in | 1200×1800 px | 600×900 px | Photo prints |
| 8×10 in | 2400×3000 px | 1200×1500 px | Framed photos |
| 11×17 in | 3300×5100 px | 1650×2550 px | Posters |
| 24×36 in | 7200×10800 px | 3600×5400 px | Large format |
| A0 (33×47 in) | 9900×14100 px | 4950×7050 px | Billboards, banners |
Note: Large format prints viewed from 3+ meters away can use 150 PPI. The eye can't resolve finer detail at that distance.
Which AI Model to Use for Print
For print, you want models that add real detail, not just sharpness. Here's the selection:
- Lumen — designed for print-grade detail. Adds texture and fine detail that holds up at close inspection. Best for framed prints and gallery work.
- Flare — general-purpose upscaler for everyday photos going to print. Natural detail recovery without over-processing.
- Mirage — for extreme upscales (4×+). When your source is very small and you need a large print, Mirage invents plausible detail. Verify the result looks right before printing.
- Visage — if faces are in the photo, run Visage first for faces, then Lumen for overall print detail.
File Format and Color Space
For print, use these settings:
- Format: TIFF or PNG for lossless quality. JPEG at 95%+ quality is acceptable for most print shops.
- Color space: Convert to CMYK if the printer requires it. Many online print services accept sRGB and convert internally.
- Bit depth: 8-bit is standard. 16-bit gives smoother gradients but doubles file size.
Step-by-Step: Upscaling for a 24×36 Poster
- Check your source resolution and orientation. A 24×36 portrait poster has a 2:3 aspect ratio. If the source differs, crop or add borders without stretching; calculate the upscale from the cropped image.
- Calculate the needed resolution: 24×36 at 300 PPI = 7200×10800 px. At 150 PPI = 3600×5400 px. Confirm PPI and bleed requirements with your print shop; swap width and height for landscape orientation.
- Upload to UpRes, select Lumen, and preserve the source aspect ratio. Choose a scale so both output dimensions meet the required pixel minimum after cropping. A 1800×2700 px source at 4× reaches 7200×10800 px. Lumen supports up to 8×, subject to plan and output-size limits. A fixed 16:9 screen preset is not a poster target.
- Download the result and verify its actual pixel dimensions against the print minimum. Check fine details at 100% zoom — fabric texture, hair, and text should look clean.
- If the required scale exceeds model or plan limits, use a larger source, a smaller print, or a lower PPI agreed with your print shop. Do not assume repeated upscaling restores missing detail. Inspect any face restoration before printing.
- Export as TIFF for the printer. If the file is too large, use JPEG at 95% quality.