Results: 720p And 1080p
Low Details @ 720p
As expected, Far Cry 4 is not a game that facilitates playable performance on low-end PCs or entry-level graphics cards. Nevertheless, you can achieve passable frame rates with sub-$100 GPUs as long as you're willing to drop your resolution to 1280x720 pixels.
If you really want to achieve at least a 30-FPS minimum, you need a GeForce GT 730 GDDR5. Aside from raw frame-per-second performance, the Radeon boards suffer more significant frame time variance. This can be a symptom of micro-stuttering, and while the lowly Radeon R7 240 will suffice if you're not a performance snob, its frame time variance is astonishingly high. We consider the Radeon R7 250X to be a good starting point for Far Cry 4, though.
Low Details @ 1080p
Let's see what happens when we bump up the resolution from 720p to 1920x1080:
The GeForce GTX 650 is forced below 30 FPS at this resolution, while the Radeon R7 250X manages to keep its frame rate higher. The GeForce GTX 750 Ti does a good job, too. Once again, the Radeon cards struggle with high frame time variance.
Medium Details @ 1080p
Let's explore what happens when we increase the detail level at 1080p:
The frame rates remain quite high for the GeForce GTX 750 Ti and up. AMD's Radeon R9 270X and 285 are hit with a lot more frame time variance than we'd like to see, but it's not so distracting in practice to render the game unplayable.
Ultra Details @ 1080p
With the ultra detail preset enabled, this game becomes much more difficult for mid-range graphics cards to cope with. Even the Radeon R9 285 drops slightly below a 30 FPS minimum, while the Radeon R9 290X, GeForce GTX 970 and GeForce GTX 980 are the only three cards able to maintain high-end frame rates. By now, we're not surprised to see the Radeons demonstrating an undesirable amount of frame time variance.