Flux 2 Fast vs Flux 1.1 Pro Ultra

The resolution gap between these models is immediately apparent in detail-heavy subjects. Pro Ultra's 4MP native output captures iris fiber patterns, individual eyelash definition, and subtle reflections that Flux 2 Fast simply cannot resolve. These aren't minor differences—they represent fundamentally different levels of image information.

Flux 2 Fast produces serviceable images at standard resolution, but fine details appear soft or merged. In an eye closeup, iris patterns become simplified, eyelashes blend together, and reflections lack definition. For any subject requiring fine detail—medical illustration, jewelry, macro photography—Pro Ultra's resolution advantage is decisive.

Pro Ultra's raw mode produces images that look like unedited photographs rather than AI-generated content. Skin shows natural variation and imperfections, lighting interacts realistically with surfaces, and the overall aesthetic avoids the "too perfect" look common in AI imagery. This authenticity is particularly valuable for documentary or candid-style photography.

Flux 2 Fast's output, while quick to generate, often exhibits the simplified rendering typical of speed-optimized models. Skin appears flatter, textures lack variation, and the overall image can feel less dimensional. The difference is especially pronounced in challenging lighting conditions where Pro Ultra maintains coherent light interaction across the scene.

Professional portraits reveal the quality gap between these models. Pro Ultra renders skin with visible pore texture and natural tonal variation, catch lights appear precisely placed and correctly shaped, and hair shows individual strand definition. These details collectively create the "medium format quality" look that professional photographers recognize.

Flux 2 Fast produces portraits suitable for quick previews but lacking professional polish. Skin appears smoothed without natural texture, hair tends toward simplified masses, and lighting effects lack nuance. For any portrait work intended for professional use, Pro Ultra's quality advantage justifies both its higher cost and longer generation time.

Flux 2 Fast's sub-second generation enables use cases that Pro Ultra cannot serve. Interactive applications requiring immediate visual feedback, high-volume batch processing, and rapid prompt iteration all benefit from 1-second turnaround. When you need to generate hundreds of test images quickly, Flux 2 Fast's speed is genuinely valuable.

Pro Ultra's 8-second generation time is a deliberate trade-off for quality. The additional compute time produces 4MP output with detail that cannot be achieved faster. For final production renders where quality matters, 8 seconds is entirely reasonable. The key is matching the model to the workflow: Flux 2 Fast for exploration, Pro Ultra for execution.

Flux 2 Fast is the budget champion, costing roughly 9x less per image than Pro Ultra. For high-volume applications where individual image quality isn't critical—generating thumbnails, testing compositions, creating placeholder content—Flux 2 Fast's low cost enables scale that would be expensive with premium models.

Pro Ultra's premium pricing for 4MP output is actually competitive per megapixel for ultra-resolution work. The question isn't raw cost but value: a single Pro Ultra image for commercial use is worth more than nine Flux 2 Fast previews that don't meet professional standards. Match the model to the application's requirements.