Final rendering images are darker than preview images

I just started web-ui based stable diffusion.

When I export the final rendered images, it’s always darker than the previous preview images, and I don’t know why.

And this is a final result(Exported files at file browser are also same.)

This is my setting and it was bbmix-ANIMEMIX, but other 2D checkpoints have same issues.

Sampling Method : dpm++ sde karras
Sampling steps : 40
Upscaler : SwinlR 4x
Hires steps : 15
Denoising step : 0.4
Upscale by : 1.5

Any advice for a newbie?

Setting screenshot for easy to see.