Background images added via VFB become grainy

For some reason the background image I add via the “Background Image” option becomes grainy. I’m using an image created in Photoshop at 3500 px width and then I do a render in Max at 800 px. The image however looks noisier than it looks in Photoshop at that resolution. Why is that? Is there something I’m missing?

Please check this screenshot:

That’s because V-Ray doesn’t apply any re-sampling on the image.
As for now it is best to use background images that matches the output resolution in order to avoid that issue.

I’ll make a note about it into our system.

Thanks for the clarification and the tip! Works as expected now.