A game reported as running at a high resolution is often rendering far fewer pixels and reconstructing the difference. The setting now describes the output, not the rendering effort.
Rendering cost scales with pixel count
Every pixel drawn requires shading work, and the cost rises roughly with the number of pixels. Moving from one common resolution to the next roughly doubles that load.
Modern effects make each pixel more expensive as well, so the combined increase can outpace what a generational hardware improvement delivers.
Rendering at a lower internal resolution and enlarging the result is the obvious response, and the entire difficulty lies in doing the enlargement well.
Reconstruction uses information across frames
Simple scaling has nothing to work with beyond the pixels in the current image, so it produces a soft result with visible stair-stepping on edges.
Temporal techniques instead accumulate detail from previous frames, shifting the sampling pattern slightly each frame so that successive images cover different sub-pixel positions.
Because the camera and objects move between frames, the reconstruction must track that motion and discard samples that no longer correspond, which is where the difficulty concentrates.
Motion is where artefacts appear
When motion tracking fails, old samples are applied to the wrong place. This shows as ghosting behind moving objects, shimmer on fine detail or smearing during fast camera movement.
Transparent effects, particles and thin geometry such as fences and foliage are the usual trouble spots, because they move independently of the surfaces behind them.
Reconstruction quality is therefore judged in motion rather than in still screenshots, where almost every technique looks acceptable.
Frame generation is a separate idea
Generating intermediate frames between rendered ones raises the displayed frame rate without reducing the time it takes for input to affect what is drawn.
Latency is governed by the rendered frames, so a smoother image can accompany a response that feels unchanged or slightly worse than before.
This is why frame generation suits slower-paced games better than competitive ones, and why the frame rate counter has become a less complete description of how a game feels.
The settings menu no longer says what it did
Two machines both reporting the same output resolution may be rendering very different numbers of pixels depending on the upscaling preset selected.
Comparing hardware or settings therefore requires stating the internal resolution and the reconstruction mode, not just the final figure.
Reviewers have adapted by reporting both, but the underlying settings menu still presents a single number that no longer carries the meaning it once did.