I've been processing film since about 1965 and this is by far the strangest thing I've ever had happen.
Here are the parameters:
Two rolls 120 processed at the same time, in the same tank using HC110 at 68-70 degrees.
Temps of all chemistry and wash water were within 5 degrees of one another.
Used a Kindermann rotational processor.
Used the appropriate time on the development chart less 20% to allow for constant agitation.
One roll was Tmax 100, the other was Ilford Pan F Plus (long outdated)....both exposed at normal film speed.
In the images below, the church doors are from the roll of Tmax which all came out perfectly.
The two frames that include the cars are from the roll of Ilford and show the strangest pattern I have ever seen on any film. It is almost like a texture screen has been applied and it matches on each and every frame throughout the roll but does not appear on any of the blank areas of the margins or between frames as you can see. No, I did not shoot through anything except clear air.
Since both rolls were processed together and under normal processing parameters, I can't imagine that this is in any way a processing artifact.
Unfortunately, I can't remember which of my three medium format cameras was used on the weird roll, but my diciest one, (an ancient Kalimar 660 which I was testing) was used on the church image and of course the rest of that perfect roll. The other choices would have been Hasselblad or Yashica Matt 124G, but this looks like no camera or lens artifact that I've ever seen. Nor does it resemble any light leak I've ever encountered.
Best guess so far came from a friend who opted for a bad roll from the manufacturer which only activated when exposed to light through the lens, but showed nothing on the cleared film areas post fixing and washing. I have my doubts, but I have no other opinions.
I am completely at a loss on what could cause anything remotely like this, so everyone, please chime in with your best guesses.
Thanks in advance.