I've recently set up a darkroom and have a question about ADOX MCP 312. According to the info sheet, 312 without any filter is a grade 2. The problem is, my exposure time for this grade is about 3 seconds, max. It's ever so slightly longer when I use the filters in the colour head for higher grades - and even shorter for lower grades. Can anyone tell me what I'm doing wrong? I should be able to have a longer exposure time, no? My enlarger is an LPL D6700 with dichroic filters. The aperture on the lens is F11. I'm processing the paper in Formulary 130, 1:1. Thanks for any info - much appreciated.