Reciprocity effect and Delta 400

I use Delta 400, 120 film and I am interested in try to make exposures around 5 to 15 minutes. Has anyone had any experiences with this and if so what was your increased exposure compensation and or change in development. I read Ansel's info in The Negative but he only goes up to 100 seconds.

Sandy King published film factors for reciprocity failure a while back for a number of films. I took that data and published chart and excel spreadsheet tables for a number of films. The metered times go to 1,000 seconds. I did not publish the times for Delta 400 but you should be able to get pretty close. You can find the chart and tables at

Dead Link Removed

Hope this helps

Mike

Thanks. Michael