HDR Effect VAE V3.0

Note: ALL METRICS use FP32 version - FP8 version is supplied for research only.

Bottom Line

HDR VAE is the recommended choice for approximately 80–90% of real-world use cases.

Although Base SDXL VAE maintains a small advantage in objective reconstruction metrics, HDR VAE consistently produces images that appear sharper, richer, more vibrant, and more professionally polished. The modest reduction in PSNR and SSIM is a worthwhile tradeoff for the substantial gains in perceived visual quality.

HDR VAE v3.0 vs SDXL Base VAE

Note: HDR VAE achieved an SSIM score of 0.8481 versus 0.8555 for SDXL Base. A small SSIM reduction is expected for an enhancement-focused VAE, and this result remains significantly stronger than previous HDR VAE versions.

Overall Results

The evaluation shows a clear tradeoff between reconstruction fidelity and visual enhancement.

SDXL Base VAE Wins

• Higher SSIM (0.8555 vs 0.8481)

• Better LPIPS (0.04136 vs 0.05392)

• More accurate structural energy preservation

• Slightly closer perceptual similarity to the original image

HDR VAE v3.0 Wins

• Sharper images

• Better edge preservation

• More accurate contrast reproduction

• Significantly larger color gamut

• Greater color diversity

• Better brightness and contrast consistency

• Reduced channel drift and improved color balance

Key Findings

Sharpness & Detail

HDR VAE preserved image detail far more effectively:

• Sharpness remained within 4% of the ground truth, while SDXL Base lost roughly 41%.

• Edge density dropped only 7.3% with HDR compared to 24.8% with Base.

• Gradient strength was also closer to the original image.

Winner: HDR VAE

Contrast & Brightness

• SDXL Base was slightly closer in absolute brightness.

• HDR VAE preserved contrast almost perfectly.

• HDR showed virtually zero brightness bias and near-perfect contrast gain.

Winner: HDR VAE

Color Reproduction

HDR VAE produced substantially richer color output:

• +37.9% LAB color volume versus -6.5% for Base.

• +16.6% more quantized colors versus -10.1% for Base.

• Fewer spurious colors and better color balance.

Winner: HDR VAE

Conclusion

If the goal is maximum fidelity to the original image, SDXL Base remains the stronger choice according to SSIM, LPIPS, and structural preservation metrics.

If the goal is higher perceived image quality, HDR VAE v3.0 delivers noticeably sharper details, stronger contrast, richer colors, better edge retention, and more accurate photometric behavior while sacrificing only a small amount of reconstruction fidelity.

In short:

• SDXL Base VAE = More faithful to the source

• HDR VAE v3.0 = More visually detailed and vibrant

• SSIM difference is small (~0.9%), while HDR gains in sharpness, contrast, and color reproduction are substantial

Recommended Use Cases

Use Base SDXL VAE when you need:

• Maximum numerical fidelity

• Scientific, medical, or archival imaging

• Close color matching to reference images

• Natural, subtle, or muted aesthetics

• High consistency across generations

• Extensive post-processing workflows

Use HDR VAE when you need:

• General-purpose image generation (recommended default)

• Photorealistic outputs with greater depth and impact

• Artistic or stylized generations

• Better detail retention in faces, textures, and architecture

• HDR-like contrast and richer color reproduction

• Strong visual appeal and presentation quality