There isn’t a universal “acceptable” amount of noise—it depends on the image, the intended output, and your artistic goals. In practice, many photographers worry more about noise than viewers do.

The key advice: don’t judge noise at 100% on screen. A 1:1 view often exaggerates noise far beyond how it will appear in a normal-sized print or normal viewing distance. Since your concern is 13x19 prints, evaluate the print itself or view the image at an on-screen size that matches the print.

Cropping heavily will make both softness and noise more obvious, which likely explains why an ISO 400 wildlife shot can still look noisy.

For reduction tools, community recommendations included Noise Ninja and Topaz DeNoise. Any noise reduction involves some trade-off with detail, so the goal is usually to reduce noise enough that it stops distracting rather than trying to eliminate it completely.

Also consider that noise can be aesthetically useful. In some images—especially black-and-white—it can add mood or atmosphere. If you’re unsure, get feedback on actual prints from other photographers or viewers rather than relying only on pixel-level inspection.