Odd patterns on negatives while scanning

I'm having these odd rainbow patterns show up when I'm scanning my negatives...The negatives appear clean and I haven't miss-handled them, as far as I know.My scanning method is to place the negatives between my light box and a small pane of glass and photograph the image with my DSLR. The pattern appears when the negative is sandwiched. When I first noticed it, I cleaned and scrutinized everything thoroughly, thinking I had somehow contaminated the film or my equipment. But I could not resolve the issue, apart from removing the film from the glass. There is no evident contamination of the film, light box, or glass. The only variable is the film. Sometimes the effect is worse than at other times...I'm not sure if a brand of film is the culprit, maybe. This particular image is TMAX100.My best guess right now is photo-flo. I add the photo-flo for 30 sec, then rinse, squeegee, and hang. IF it is Photo-flo, what could I do to remedy the problem?Has anyone seen this issue before?I'm asking before doing too much testing on my own...due to not wanting to handle my negatives more than is necessary.

Lazlo said:

.My scanning method is to place the negatives between my light box and a small pane of glass and photograph the image with my DSLR. The pattern appears when the negative is sandwiched..

Click to expand...

Newton rings - a phenomenon in which an interference pattern is created by the reflection of light between two surfaces

Often happens with glass negative carriers. To avoid, some negative carriers use slightly etched anti-Newton rings glass.

High-end scanners avoid this by using oil immersion of the film between the glass.

Try putting the emulsion side next to the glass on your light box and simply tape the edges of the film to that surface (skipping the cover glass).

Thank you! After googling it, that's exactly what's going on. Now I know who my enemy is!

cut out a hole in a piece of sheet film the size of the frame of film. Place that piece of film between the condenser and the negative. Problem solved.

Or find some anti-newton glass to put over the condenser surface.

Try flipping the film so the other side touches the glass instead

DSLR on A.P.U.G....

get a sheet of enlarger anti newton glass and then sandwhich film between AN glass and clear glass with emulsion side facing clear glass side. Photograph from clear glass side.

If the negative carrier from an enlarger holds the negative flat enough for enlarging, it holds it flat enough for copying as described above. One can place the film in a negative carrier and place the carrier on the light box. A more compact substitute for the enlarger's negative carrier can be improvised if much negative copying is needed. Properly stored negatives are flat enough without being sandwiched between glass or held in frames to flatten them. They merely have to be held out of contact with the glass of the light box.