Not always, just from time to time, I'm discovering these cloud-like artifacts on my 4x5 film shots. They are present on the film itself; it's not scanning artifacts. Artifacts can be present on different film types (first photo is EKTAR100 color negative, second is EKTACHROME E100 slide). These two shots were done with different cameras but with the same film holder.
The cloud-like artifact pattern is always different on every frame that has them.
First, color and B&W images are the same. Second, only one color channel with curves adjustments can make the artifacts more visible. On the B&W image, notice that the cloud-like artifacts have quite the same silhouette-like exposed part of the frame, but with an offset. The silhouette is a TOYO 4x5 film holder inner ledge for holding the film frame.
On the first photo, the artifact structure on the right side of the frame is more shallow than on the rest of the frame.
Any thoughts on the source of the color noise?