FLUX.1 SmartUpscaler-[2Pass Upscaler]. ControlNet + SD UPscale

   This workflow designed to restore, upscale and color fix low resolution realistic images and portraits (blury and non-blurry aswell) using FLUX.1 models. Allows you to output 4Megapixel+ images.

Important Usage notes:

jasperai/Flux.1-dev-Controlnet-Upscaler · Hugging Face    By default any image you load (even 256x256 image) will be resized to match 1Megapixel, which is base resolution for FLUX.1 model. This setting can be altered in - "Image Input Resizer" nodes. After that, this resized image will be upscaled by whichever value you have in Ultimate SD Upscale node.
   Prompt is not mandatory, but can help if you get unstable results, as well as denoise values.
   You can still use value "Image Upscale_by = 1", in that case upscaler will act as an image refiner.

   For celebrity images or characters it's better to use celebrity/character designated Lora to preserve accurate facial features.

You can also try out this workflow as an AI-app:

https://www.seaart.ai/workFlowAppDetail/cti9f9le878c73dh27ig