Discoloration in camera scans

Discoloration in camera scans

I’ve recently done my first own digital camera scans, after previously letting my lab scan all my 35mm negatives. I use my Canon EOS RP with an adapter for Olympus OM-system lenses and a Zuiko 50mm f1.8 lens with extension tubes. I used my iPad as a light source, in a dark room. As a film holder, I use a 3D printed holder. I did shoot the “reflective” side of the negative, which I have seen people say could lead to issues. Haven’t tried shooting the other side of the film yet. I also didn’t block out light coming through the sprocket holes, which I didn’t know I was supposed to at first.

In these scans I experienced a very awful looking yellow-ish band (as seen in the image below). It’s present in a lot of images, most obvious in bright photos of skies etc., and always in the same place. You can see it in some darker images as well, but not all. I obviously don’t have a perfect setup, so there’s a lot of places where issues could arise. Because of this, I don’t know where to start debugging, and all help and pointers as to what could create such problems is much appreciated. I tried using my parets very basic 35mm film scanner and the discoloration was not visible there, so I know it’s something in my scanning process.

Thanks in advance!
Skärmavbild 2024-01-25 kl. 21.43.42

Presumably you’re talking about colour transparencies rather than negatives but it would be useful to have confirmation. A standard ‘non macro’ lens with extension tubes is not ideal and appears to be causing vignetting in the corners but it wouldn’t cause this of course. It’s likely to be a reflection off the top of the film I would have thought, possibly originating from the light coming through the sprocket holes and reflecting off your lens. Is it not visible through the viewfinder when you take the shot?

(Edited when I got my brain in gear)