I have used Delta 100/PMK for years. It is my favorite combination for blazing sharpness and vanishingly low grain. I rate D100 at 50 and develop for 14 min @ 68F. EI 64 would most likely be fine. I wouldn't change the dev time for such a small difference in EI. The negatives are easy to print and have a special 'beauty' quality to them. Good luck.(posted 9139 days ago)