Chosen Solution
When I compare the display on my iMac with an external LG monitor of the same size and the same age, the Mac display seems pretty dim and lackluster. Is the comparison fair; i.e., is it normal for an iMac display to look dim when compared with an external monitor? Or, does the bulb and/or other components need replacing?
External video is not the same as onboard video. It is possible your backlight is failing - it will dim as it does (or it may just suddenly go out). You’re comparing Apples to Oranges. If this answer is acceptable please remember to return and mark it.
