Delta 400 is EI:250. FP-4+ is EI:80. Tri-X (35mm) is EI:250. Tri-X pro is EI:320. HP-5+ is EI:400. Tri-X (35mm)is very foggy, not a great film. HD curve is S shaped: long toe, early shoulder. HP-5+ has a virtually straight line HD curve and is a true 400 speed. Can't say much about Plus-X, fairly decent. FP-4 is notably superior with virtually no base fog. FP-4+ and HP-5+ are spectacular films. Are you using plain water stop and Formulary TF-4 fixer?(posted 8697 days ago)