Light leak or development issue?

In the adjusted levels image, it almost seems as if something photo active has contaminated the reel and is leaching out onto the film edge.

Do you use a variety of developers? Could there be a pattern of this occurrence when you switch from a certain developer to another?

How old is the reel? I assume it is a plastic reel; correct?

Could it be absorbing some developer or simply breaking down a bit and causing a chemical reaction that is somehow superadditive to the developer?

Your agitation is 3-4 inversions every minute, but is your tank completely full? It looks like there's a "clustering" of activity around the reel, either due to lack of agitation or, like @Kino said, too much stuff on the reels. Silver and dirt builds up on plastic reels, after use, and can be cleaned off using potassium dichromate bleach and a brush.

Kino said:

In the adjusted levels image, it almost seems as if something photo active has contaminated the reel and is leaching out onto the film edge.

Do you use a variety of developers? Could there be a pattern of this occurrence when you switch from a certain developer to another?

How old is the reel? I assume it is a plastic reel; correct?

Could it be absorbing some developer or simply breaking down a bit and causing a chemical reaction that is somehow superadditive to the developer?

Click to expand...

Plastic reel, maybe 3 years old. This has crossed my mind, though not dev since I haven't used anything but DD-X for two years, but I had thought possible leftover wetting agent residue. Since considering this though I have been washing the reel extra thoroughly. Are the plastic reels really that porous that the chemical make-up could change over time? I guess fixer would be the biggest factor if so? I have a spare reel which I can try, just to add another layer of superstitious ritual to proceeedings. I might end up with eye of newt or toe of frog in my developer at this rate!

Don Heisz said:

Your agitation is 3-4 inversions every minute, but is your tank completely full? It looks like there's a "clustering" of activity around the reel, either due to lack of agitation or, like @Kino said, too much stuff on the reels. Silver and dirt builds up on plastic reels, after use, and can be cleaned off using potassium dichromate bleach and a brush.

Click to expand...

Tank is 550ml full, used to be 500ml, but I had bubbles down the edge. I'd like to think you are right about the clustering thing, but as I say, I've had rolls with 90% sky which have come out perfect, then the next roll every sky shot has this problem, with no change at all in my regime.

Typical extra edge density from turbulence during agitation. 120 film is especially prone to this problem. You need to experiment with amounts of developer in the tank and agitation schemes until you find a combination that gives you even development. FWIW, I spent two days and 10 or so rolls of film finding my sweet spot some 30+ years ago. I'm glad I shoot LF now...

Doremus