i realized that i have the gel holder instead of the filter holder
its very sharp...even at 3.5
There's three kinds of filter holder:
Gel holder (I think you can fit a naked glass in the gel holder, maybe a 40.5mm or 42mm glass)
Filter holder (39mm thread)
Polarizer filter holder (the official one is C-PL1S, but the C-PL2S can be fitted)
The polarizer filter holder (+included filter, special with a gear around it) commands horrible prices: seen at up to 400$, but sometimes you can find a reasonable seller (bought mine for 65,40€)
There is a neat system for turning the polarizer without removing the filter holder, including photos
Here you can find a compatibility chart for all the drop-in filter holders:
https://www.nikonimgsupport.com/eu/BV_article?articleNo=000005861&configured=1&lang=en_GB&setRedirect=trueIn the chart, it is stated that the C-PL2S is incompatible with the 400/3.5, but I was able to fit it by using a rectangular piece of black closed cell foam, which moves it out by about 6-7 mm.
The springy action of the foam holds it firmly in place so it does not rattle.
Ciao from Massimo