120Hz/240Hz Variable Refresh Rate (VRR) & G-Sync: Saccadic Motion Blur Optics

Unlike old CRT monitors that illuminated pixels with instantaneous phosphor flashes, modern LCD and OLED displays hold each frame continuously on screen until the next refresh cycle (Sample-and-Hold).

When you scroll a webpage at 60 Hz while tracking a line of text with your eyes:

$$\text{Eye moves continuously at } \mathbf{v} \quad \text{vs.} \quad \text{Display holds static frame for } \mathbf{16.67\ \text{ms}}$$

While your eye smoothly tracks across the display, the static image is held frozen for 16.67 ms. This velocity mismatch causes the image to physically drag across your foveal photoreceptors: Retinal Slip. Text smears into a blurry, illegible ghost trail!

Motion blur on modern screens is governed not by pixel transition response time (GtG), but by Motion Picture Response Time (MPRT):

$$\text{MPRT} \approx \frac{1}{\text{Refresh Rate}} \quad \longrightarrow \quad 60\ \text{Hz} = \mathbf{16.7\ \text{ms}} \quad \text{vs.} \quad 120\ \text{Hz} = \mathbf{8.3\ \text{ms}} \quad \text{vs.} \quad 240\ \text{Hz} = \mathbf{4.2\ \text{ms}}$$

At 120Hz and 240Hz, frame persistence drops by 50% to 75%. Moving text remains pin-sharp during fast scrolling, eliminating the need for constant micro-saccades and refocusing.

When frame rates fluctuate out of sync with a fixed 60Hz display, frame judder and tearing occur. The brain struggles to integrate these micro-stutters with vestibular motion cues, inducing subtle motion sickness and nausea. VRR / G-Sync dynamically synchronizes panel refresh to graphics rendering, delivering rock-solid optical smoothness that minimizes digital asthenopia.