Field Of View Scaling
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Some games specify FOV as horizontal, others as vertical or diagonal, and the same number under a different measurement convention produces a visibly different view — converting between them is necessary before comparing FOV settings across games.

The conversion depends on the display's aspect ratio; vertical FOV is generally derived using the arctangent of (tan(horizontal FOV/2) divided by aspect ratio), then doubled — this is why the same horizontal FOV looks different on a 16:9 versus an ultrawide monitor.

Standard rectilinear projection (used by most game engines) inherently stretches objects further from the center of the screen as the FOV widens, which is a geometric side effect of projecting a wide field onto a flat screen, not a rendering bug.

A wider aspect ratio (like an ultrawide monitor) shows more horizontal content at the same vertical FOV, so matching a comfortable FOV from a standard monitor to an ultrawide typically requires converting via vertical FOV to preserve the same effective vertical view rather than keeping the horizontal number identical.

A wider FOV shows more of the environment at once, which is generally useful for peripheral awareness, but it also makes distant objects appear smaller and more distorted at the screen edges, so competitive players often balance FOV against target visibility rather than maximizing it outright.