Scale Factor

Also known as: scale, scale_factor

Scale factor controls the upscaling multiplier for super-resolution models. A scale of 2 doubles the image dimensions, 4 quadruples them. Higher values produce larger images but take more time and can introduce artifacts if pushed too far.

What It Does

Super-resolution models like Real-ESRGAN take a low-resolution input image and upscale it to a higher resolution while adding realistic detail. The scale factor determines the multiplier applied to both width and height. A 512×512 image at 2× becomes 1024×1024; at 4× it becomes 2048×2048.

The model doesn't simply stretch pixels — it intelligently fills in detail that wasn't present in the original, using patterns learned from training data. Higher scale factors require more computation and more "hallucinated" detail. For most use cases, 2× or 4× is sufficient. Pushing beyond 4× often introduces visible artifacts or overly smoothed textures.

Value Ranges

2× Scale

Doubles dimensions (4× pixel count). Fast and reliable. Best for images that are slightly undersized.

3× Scale

Triples dimensions (9× pixel count). Good middle ground for moderate upscaling.

4× Scale

Quadruples dimensions (16× pixel count). Maximum commonly supported. Good for significant upscaling from small originals.

Visual Comparison

Image pending

scale = 2

Image pending

scale = 3

Image pending

scale = 4

Tips

2× is usually sufficient for web display and general use.
4× is ideal when you need print-resolution output from a generated image.
Upscaling an already high-resolution image wastes time and credits with minimal benefit.
For best results, generate your image at the model's native resolution first, then upscale as a separate step.