Using the red #25 filter drops your film speed by two stops. By rating your film of 400 at 200 you have already compensated by 1 stop. You can compensate the other stop in the development by overdeveloping. Your developing time will depend a lot on what developer you intend to use. Also take into consideration under what conditions you exposed your film at (cloudy, hazy, flat lighting) you may want to overdevelop just a bit to bring out some contrast in the low-lights. You did not mention what your reasoning was for using a red #25 filter to begin with. What are you looking for in your end result in your image?(posted 8641 days ago)Rhonda