For photo editing, there isn’t one fixed brightness setting for every screen. The key is to match the display to your viewing environment and, ideally, calibrate it with hardware.

A common target for editing is about 120 cd/m² (nits) for monitor white, with controlled ambient light. If the room is dark, a screen set too bright often leads to edits that come out too dark elsewhere. That’s why many uncalibrated displays cause problems: they’re usually set much too bright.

Good practice:

• edit in consistent, controlled room lighting
• calibrate the monitor with a hardware calibrator if accuracy matters
• keep monitor and ambient white point matched, commonly D50 or D65

If you don’t have a calibrator, a useful rule of thumb is that screen white should look about the same brightness, or only slightly brighter, than a sheet of white paper viewed in the same light.

So no, your laptop and desktop do not need to use the same percentage brightness setting. Different displays have different maximum brightness. What matters is that both are adjusted to a similar calibrated output for your room, rather than simply “as bright as possible.”