I'm not familiar with the calculation of the metrics by WPT and Lighthouse, but per your description the one that should be more closely related is Perceived Render Time.
The perceived render time represents how long the initial visible page takes to load.
With usual text / image size ratios the value largely depends on the loading time of the slowest image within the page's visible range.
Hi Gabriel thanks for the info. In looking over the documentation it appears the timing is based on images. However, what happens if the page has no images but rather other elements such as text. The only way I think I can get this is by adding a user timing metric.
Klaus - the timeline looks awesome. Questions.
If a W3C performance mark is inserted into a web page to measure the rendering of an element such as a hero image, data grid, etc, will those timings be displayed on this timeline. I am referencing https://www.w3.org/TR/user-timing/ and article on this here https://speedcurve.com/blog/user-timing-and-custom... - Basically I want to know when an element such as hero, or data grid actually became visible. Perhaps there is another way to do this. Until now I typically look at the filmstrip in WPT, but using the marking is more accurate.