So I’m seeing something that I don’t think I’ve seen before. I’ve been testing a few papers for use in paper negative and direct positive processes. Twice now, I’ve been able to replicate the same behavior. Currently, I’m looking at Ilford Coldtone VC fiber paper (for direct positive but the development of the neg is the same as for paper negative essentially). Initially, I tested for speed using the step-exposure method. I used probably f8 or f16 when I did this. I got a paper speed of ISO 6 + 3 stops (I use a Pentax Spot meter that only goes down to 6 so I add the additional stops). This yields a good negative on this paper which would stand on its own as a paper negative and reverses well into a positive image. The problem now is that if I shoot the lens wide open, it is not following the same speed rating and the image area is totally exposed to black (negative) with no image detail. Complete total overexposure. Stop it down and use the same speed rating and the image forms correctly. I’m changing nothing else in the workflow. The only difference is the aperture used for the exposures. Has anyone experienced anything like this?

And as far as the lens, I’m using a 10 3/4” Goerz Dogmar f4.5. The only thing I could think of was if the lens (it’s an old lens) somehow has an aperture not conforming to modern standard. It doesn’t have a typical f-stop scale and instead reads: f4.5, f5, f5.5, f6.8, f8, f16, f22

Any insight would be appreciated.