Mamiya RB & RZ67: mysterious spots on negatives?

Ever since I bought and began using an RB67, I have noticed from time to time two white, undeveloped spots on frame #1 of my negatives, about 1/2" into the frame from the "leading edge" of the roll. They have bedeviled me for months, and I could NOT determine their origin. Now I have.

That "leading edge" is where the masking tape sticks the film to the paper backing. I customarily insert this end into the center of the developing reel, after tearing the film away from the paper backing. The length of tape remaining on the film seems to grip quite well the spring clip on the developing reel.

The spring clip is the culprit. Its two "legs" are crimped around one of the transverse rods that keep the sides of the reel separate. When you wind the film onto the reel, it comes in contact with the two crimps of the spring clips, and prevents the developer from reaching the surface of the film.

Ordinarily, this won't be a problem, if the point of contact falls outside the area of the first exposed frame. But the matching-arrows configuration in the RB film backs I have--that tell you when to stop winding the film and close the back--place the first frame too close to the attaching tape.

The answer is simple enough. DON'T stop winding the paper leader ahead when the arrows coincide. Instead, crank it ahead another half inch.

I don't know if anyone else has had this problem, and I don't know if my explanation here is clear enough, but if the answer to both questions is "yes," maybe this harangue will be of help.

R.W. Behan

R.W. Behan wrote:
Ever since I bought and began using an RB67, I have noticed from time to time two white, undeveloped spots on frame #1 of my negatives, about 1/2" into the frame from the "leading edge" of the roll. They have bedeviled me for months, and I could NOT determine their origin. Now I have.

That "leading edge" is where the masking tape sticks the film to the paper backing. I customarily insert this end into the center of the developing reel, after tearing the film away from the paper backing. The length of tape remaining on the film seems to grip quite well the spring clip on the developing reel.

The spring clip is the culprit. Its two "legs" are crimped around one of the transverse rods that keep the sides of the reel separate. When you wind the film onto the reel, it comes in contact with the two crimps of the spring clips, and prevents the developer from reaching the surface of the film.

Ordinarily, this won't be a problem, if the point of contact falls outside the area of the first exposed frame. But the matching-arrows configuration in the RB film backs I have--that tell you when to stop winding the film and close the back--place the first frame too close to the attaching tape.

The answer is simple enough. DON'T stop winding the paper leader ahead when the arrows coincide. Instead, crank it ahead another half inch.

I don't know if anyone else has had this problem, and I don't know if my explanation here is clear enough, but if the answer to both questions is "yes," maybe this harangue will be of help.

R.W. Behan

I use the Paterson tank and reels so I do not have this problem; the
film is fed by two ballbearings on the sides of the reels unto a spiral
groove on the reel. I like it because there is never the risk of the
film jumping into another groove and touching another part of the film.
It is a lazy way, but it works.

RobGN