Before we move onwards into the conclusion it is handy to know how much graphics memory the game requires in a preferred resolution. You'll notice that 2GB graphics card are sufficient and that's the number this game has been aiming on. A graphics card with 2 GB of graphics memory minimum is really recommended by us. Should you have less available and run into performance issues, the easiest way out preventing frames from being swapped back and forth in that frame buffer is to select lower quality settings or disable AA levels.
Above you can see a wide variety of in-game selectable quality modes @ 2560x1600. We switch in-between the image quality modes (Low to Ultra) to monitor frame buffer utilization. As you can see we are hovering at the 1.5 GB of graphics memory with FXAA enabled starting at High quality mode settings already. Once you increase the quality settings towards Ultra mode you start to reach a turning point where the game almost hits 2 GB of graphics memory. The measurement shown above is fairly similar and applicable for 1920x1080/1200 and 2560x1600. Now not everywhere in the game that much graphics memory is used, but there are some critical points in-game where you will reach or even pass the 2GB in combination with the highest quality modes. If you'd apply an exclusive AA mode like MSAA though graphics card drivers, we have no doubt you'll breach the 2GB threshold. So be careful with that.
Overall the advise is simple enough, make sure you have a graphics card with 2 GB of graphics memory when using High to Ultra image quality modes. Please keep in mind though that memory utilization will vary a bit per level, it's not a very precise thing to measure. As such take these values as an indication, not a precise measurement.
Anyway, 2GB minimum for your graphics card, it is the magic number to find Elizabeth ;)
Summing it up
All modern mainstream and better graphics cards starting at mid-range will run the game at Full HD (1920x1080) in combo with Ultra settings well. For mid-range the 7800 series from AMD and the GTX 660 series from NVIDIA will offer truly nice value for money and that's where we as PC gamers need to be. We do not like to forfeit in quality.
If you need a little more icing on top of the cake then the GeForce GTX 660 Ti is great, while on the competition's side the Radeon HD 7950 Boost editions being very price competitive as well -- single GPU wise. From there upwards you pay the price for premium products and the value for money ratio slowly is killed off. At 2560x1600 with Ultra Quality settings the more high-endd cards currently available can manage really well. Please do bear in mind that our tests are based on averages, so YES there will be times your FPS drops to 25 fps in big fights and explosions, even with GTX 680, R7970 or a Titan.
I also want to point out, all cards used today are reference cards with reference clocks. As you guys know AIC/AIB partners mostly offer factory overclocked or factory faster clocked products. That by itself can shift performance per card or brand upwards another 10% -- just so that you guys know okay?
We use Windows 7 64-bit SP1 all patched up. Each card runs on the same PC with the same operating system clone. GeForce cards use the latest 314.22 WHQL (download) and for AMD Radeon graphics cards we used the latest 13.3 Beta build 3 driver (download). Both NVIDIA and AMD have released these drivers being optimized for Bioshock Infinite (and Tomb Raider).
As always, we hope you enjoyed this selection of measurements. One last small tip, if you need extra performance, disable VSYNC in game. It seems that the game engine locks and regulates your framerate fixed to the closest target which often can be either 30 or 60. Disable it and your graphics card will get a lot more to do, but at the cost of screen tearing.
Last and final note, as always with thesew guides, this article was rushed a little as such it still is pending a grammar check. So forgive me the a-typical mistakes.