How to Upscale an Image Without Losing Quality (AI vs Traditional Methods)

Why Images Lose Quality When You Upscale Them

Traditional image upscaling — stretching a small image to a larger size — works by interpolating between existing pixels. The most common algorithm is bicubic interpolation: for each new pixel it looks at surrounding pixels and calculates a weighted average. The result is smooth but visually soft — the enlarged image looks blurry because it is inventing pixel values from averages rather than real detail.

How AI Upscaling Is Different

Real-ESRGAN (Real-Enhanced Super Resolution Generative Adversarial Network) works differently. Instead of averaging existing pixels, it was trained to hallucinate plausible detail. Real-ESRGAN was trained on millions of high-resolution/low-resolution image pairs. It learned what a brick wall at 4× resolution looks like, what fur looks like up close, what text sharpens into. When it upscales your image it is not interpolating — it is reconstructing detail based on learned priors.

Comparison: Bicubic vs Lanczos vs AI

Method	Quality	Speed	Cost
Bicubic	Blurry at 2×+	Instant	Free
Lanczos	Slightly better than bicubic	Instant	Free
Real-ESRGAN (AI)	Sharp, detailed at 4×–8×	2–10 seconds	Free on Brush
Topaz Gigapixel	Excellent	Minutes (local GPU)	$99 software

Step-by-Step: Upscale with Brush

1. Go to Image Upscaler. No signup required.
2. Upload your image. JPEG, PNG, WebP, HEIC, AVIF supported. Max 50 MB.
3. Choose your scale factor: 2×, 4×, or 8×. For most uses, 4× is the sweet spot.
4. Toggle Face Enhance if your image contains portraits.
5. Preview the result with the before/after slider.
6. Download. Output is always PNG to preserve the new detail without JPEG re-compression artefacts.

Choosing the Right Scale Factor

• 2× upscale: Your image is already reasonably sized but you need slightly more resolution. 1080p → 2160p (4K). Fast, minimal artefacts.
• 4× upscale: Shot on an older camera or low-resolution phone, or printing at large format. This is the most popular option.
• 8× upscale: Very small source image (e.g. 500×500 px) and you need a large output. Some AI hallucination artefacts may appear on extremely degraded inputs.

What AI Upscaling Works Best On

• Portrait photos — Real-ESRGAN with face enhancement recovers skin texture, eye detail, and hair definition cleanly.
• Product photos — Objects with defined edges and textures scale well.
• Landscape photos — Sky, foliage, and buildings all benefit from texture reconstruction.
• Old photos — Even degraded scans from decades ago can be meaningfully enhanced.
• Text in images — Logos, signs, and UI screenshots sharpen noticeably.

Harder Cases

• Heavily compressed JPEGs — JPEG compression artefacts can be amplified. Use Image Compressor to produce a clean source before upscaling.
• Out-of-focus blurs — Upscaling cannot invent focus. Genuinely out-of-focus images will still be blurry, just at higher resolution.
• Abstract or painterly images — AI models trained on photography may add photographic texture to artwork. Use the 2× option for paintings.

Printing Upscaled Photos

Original size	After 4× AI upscale	Printable at
600×400 px	2400×1600 px	8×6 inches at 300 DPI
1200×900 px	4800×3600 px	16×12 inches at 300 DPI
2400×1800 px	9600×7200 px	32×24 inches at 300 DPI

Frequently Asked Questions

Does it invent detail?

Yes — if your image is extremely degraded, the AI will reconstruct plausible detail that was not technically there. This looks good but is not precisely accurate to the original.

How big will the output file be?

A 4× upscale of a 1 MB JPEG will produce a PNG of 10–30 MB. Compress after upscaling if you need smaller files for web use.