Question about a light yellow filter

[Steve Mack]

I bought a light yellow filter for B/W work, and the filter factor is 2x. I should know the answer to this, but I'm not sure, since I haven't used a filter in forever. Do I open one stop to compensate?

Also, if I want to reset my light meter to be able to read values directly, where would I set the ISO on the dial for ISO 400 (Kodak Tri-X.)?

Thank you to all who reply.

With best regards,

Stephen

 

[Ian David]

Stephen -
If the filter factor is 2x, you need to give your film an extra stop of exposure, eg open up one stop. Or set your light meter as if you are using ISO200 film. (It may help you to think in terms of slower film requiring extra exposure.)

Ian

 

[Sirius Glass]

A light yellow filter K1 is a half stop more exposure.
A medium yellow filter K2 is a one stop more exposure as posed in post #2.

 

[Kevin Kehler]

Rule of thumb, one full stop like stated above. If using through-the-lens metering, let the camera do its' own compensation (set at 400 ISO and let camera compensate the stop). If using a spot meter, hold the filter in front of the spot meter to compensate as the light might be different depending on what is being metered.