FLUX Chroma (The Perchance T2i model)
podvornyakva @ podvornyakva @lemmy.world Posts 0Comments 1Joined 1 day ago
First thing first - it IS a Chroma model... whatever version it is. Base seed match exactly. About that prompt. It is too cheap. You can't replicate nothing with that. Nobody can.
To the point. 'text-to-image' use simple approach to feed Chroma model. It is a two-pass sampling. First pass image used by second pass. 'text-to-image' gives user only first/base seed. The second seed is unknown. It is random. Second seed makes variation of the base image. With only base seed you can't reproduse same result. Neither in Comfy UI nor on web page of "text-to-image. Even with very detailed prompt. Hope i've made it clear.
To deteils. "Seven is the number of magic" Shocking Blue.
So there is a two KSampler nodes in workflow. First KSampler pass latent output as the source of second node latent input. Base KSampler set 3.5 guidiance and 1.0 denoise. As a Chroma creators recomedation. To mix in a second-pass image necessary to low down denoise factor of the second KSampler. Let's say we wana spare noise factor in final image from both pass. How do we make it? Simple - we set denoise factor to 50% of the second KSampler. 0.5. But here is the "magic". 50% denoise do not make spare influence. In fact - we get 25% influence from the second pass. Why? because of guidiense. It is halfed to. We halfing overal noise factor. Like we make transparent image on top of another image. Transparent image got only 50% of ALL it's values. Hue, luma, color, etc. Same happening with KSampler denoise.
And what should we do, to solve this issue? Right - we set guidiance to 7, doublind influence of the second pass noise. Simple. Recomended steps for sampling is 26. I use 16 for the first pass and 32 for the second. About resolution. To match "text-to-image" seed base image must be same size and orientation. Second image size may differ, but it leads to errors in image: extra fingers, extra hands and so on. It is happen because of streching latent image. To avoid those errors scaling factor must be 0.25, 0.5, 2.0, 4.0, etc.
Probably the Chroma setup for "text-to-image" plugin much more complex than that. But it's all up to you. Hope it was usefull. SYA.
P.S. As you can see here, high steps change nothing... mostly, while second pass makes drastical changes of base image. Still high-step base image makes final image details sharper and clear.
first image 16 steps, third 3 image 52 steps, second image pass 2, 32 steps)
Here is a Chroma fp8 e4m3fm scaled. Detailed prompt. 32/32 passes.
One issue that i can't solve is a CYAN color. All output, more or less, have a bluish look. I'm trying to get rid of that with help of LoRAs, but got no success yet. Any suggest?