Like @davescm, I did some comparative testing of my own between Photoshop versions 20.0.7, 22.5.4 and 23.3. Using mouse, Modifier Keys panel (double-click Shift to lock it), doc size mentioned above, click once top left, move mouse to bottom right corner, click and start clock at the same time, stop timer when stroke reaches cursor location (repeated 3x). Made sure Rulers were not shown and workspace (panels shown) was the same. Results: 20.0.7: average time was 5.5 sec 22.5.4: average time was 7.7 sec 23.3: average time was 6.3 sec * Timing and performance will vary per machine/resources.
Here area a few things you can tweek to improve speed: In Brush Settings panel > Brusth Tip Shape: increase the Spacing. Sometimes hiding certain panels can speed things up (i.e. Navigator, Brush Settings, etc) Turn off or lower Smoothing Switch from 16bit to 8bit (I realize this might be a deal breaker). Different zoom magnifications can affect performance
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