I would guess that you are using the 120 version of the Delta 3200. Unlike most 120 films, the Delta 3200 has a base fog similar to that of 35mm.(posted 8176 days ago)The 35mm version is still a little more fog than most other 35mm films, but not enough that most people notice it. For both formats, the base + fog for fresh film will run in the range of 0.38-0.45.
David Carper ILFORD Technical Service