Image Sharpness

[jujubee]

Not sure if this is mostly a function of the Denoiser (from what I've read), but I'm trying to figure out ways to render out a terrain with sharper trees in the distance.
Using VRay Physical Cams. There's almost as if there's a slight blur in the distance being applied.
While I realize this might be optics, my client is not being easy about this.

Are there any other suggestions?

[npg]

Yes, the NVIDIA AI denoiser is known to reduce sharpness a bit. Unfortunately we can't fix that until we get a better neural net. (I'm assuming you've tried increasing samples and the result can no longer improve)