Orange filter vs. no filter OM2n 28mm f3.5 lens.

http://www.flickr.com/photos/6222653...7629961032651/

That was at 6.75 in Tmax 1:4. Clearly no filter needs even more time... so far only the yellow filter seems worth using. I'm not sure how much to increase development for EI25 filterless, but everything is vastly blown out.