Best way to enlarge the image without creating noise or cause the photo to pixelate?

[MrCameraMan]

I have high resolution digital image (300ppi, 96MB) that measures 8005x4191 px (1.91x1 crop ratio) that needs to be made into a 20 foot x 24 foot mural.  I realize that there will be a change in ratio.  What is the best way to enlarge the image without creating noise or cause the photo to pixelate?  Thanks!

[D Fosse]

If you want it to look its absolute best, don't upsample at all! Despite what most people believe, it never helps. It can never be better than the original.

Concentrate on optimal sharpening instead, that has much bigger impact.

Upsampling is just to avoid visible pixels. If that's not an issue, upsampling serves no purpose. All it does is disrupt the pixel structure and introduce artifacts. Here you will end up somewhere around 30 ppi, which is more than good enough for large format reproduction to be seen from far away.

If you must upsample for whatever reason, the game is to minimize the damage. At the moment, the best upsampling method is to go back to the original raw file and use Super Resolution in ACR or Lightroom. It will have the least amount of artifacts.