I wasn't sure where to post this video, as it shows me working with my 14x17 DIY camera, with XRAY film, developing it in the darkroom, and then making a kallitype print from one of the negatives. @MattKing if it's in the wrong place, please feel free to shift it. Thanks!
Not for me and this X-ray film. I've been using this combo since 2008. The same goes for HP5, Acros, FP4, Pan F.... Manufacturer's recommended factor is too high for me. 1 stop maintains zone III density. A densitometre confirms this for me, as well as a print.
That's what I thought also. Some of the manufactures don't publish the filter factor with the specifications anymore - probably because filters nowadays are used with in-camera metering systems. I recently purchased a yellow 15 4x4 filter and measuring against the blank white of my laptop screen it indicated a 1-stop loss. Then I took the filter outside and held it up against the blue ski opposite the sun and sure enough it measured 1-2/3 stops. I theorize that the difference in the readings can be attributed to the lighting source.