Step900 PDD: darker/desaturated colors, softer motion details, and possible motion damping
Hi, I have been testing the step900 LoRA + step900 PDD heads on MiniMax H3 Ref2VA and noticed a few consistent quality differences compared with the original non-PDD 20-step generation.
My PDD tests were mainly done at 8 steps, since 4 steps showed more obvious generation errors in some scenes.
The main differences I noticed are:
Consistent darker / grayer color tone
- PDD outputs tend to look noticeably darker and less saturated.
- The original 20-step Ref2VA output preserves the colors of the reference image much better.
- This seems fairly systematic rather than normal seed variation: multiple PDD generations showed a similar gray/dark bias.
Slightly softer fine details, especially during motion
- Fast-moving hands can look slightly blurred or less well defined.
- Clothing edges and other small details during motion also look softer than the original 20-step output.
- 8 steps improves this compared with 4 steps, but it still does not quite reach the detail quality of the original 20-step sampling.
Possible reduction in motion intensity / speed
- At first I thought the motion was clearly slower and had a smaller range of movement.
- After closer comparison, the difference is not very large and some of it may be perceptual.
- However, I still occasionally get the impression that strong/fast motions are slightly smoothed, damped, or less energetic with PDD.
I am using the step900 checkpoint, not step600.
The overall motion and structure preservation are actually quite good, so the PDD model is already very useful. The most reproducible issue on my side is the global color/tonal shift, followed by slightly softer high-frequency motion details.
It may be worth checking whether the PDD heads or student LoRA introduce a systematic bias in low-frequency luminance/chroma components, and whether fast-motion/high-frequency details are being slightly over-smoothed during distillation.