Hello @marcandre , thanks for posting to the FME Community! Majority of our raster readers (GeoTIFF included) will only read a single pyramid level, which by default, will be the highest resolution or "Densest" level (is this what you mean when you say "dense level"?).
To summarize, you shouldn't need to do anything, reading the dataset will do what you're looking for by default. Best, Kailin.