[BigMackCam]

I have what is probably a very dumb question that thoroughly betrays my lack of detailed knowledge in chemistry and physics

I'm in the process of designing a product for personal use in digitising negatives, and my current design involves several magnets to hold components together whilst allowing them to be separated and moved / adjusted as required. My question: Can magnets have a detrimental effect on developed negative film, either B&W or colour? If so, could this occur within a short time period (a few minutes or hours), or would it be over much more extended timescales?

Many thanks in advance!

[Digitalis]

Can magnets have a detrimental effect on developed negative film, either B&W or colour?

No. Without going into the physics of magnetism standard Silver halide and development products, along with colour film dyes are completely impervious to magnets.

[BigMackCam]

No. Without going into the physics of magnetism standard Silver halide and development products, along with colour film dyes are completely impervious to magnets.

Thank you so much - both for the short, unambiguous answer and for not going into the physics, which would assuredly go straight over my head!! Much appreciated

[Digitalis]

or the short, unambiguous answer and for not going into the physics

You are lucky it's 7AM here and I haven't had my coffee yet.

[UncleVanya]

The only caveat is for the defunct APS film format which uses magnetic media to hold exposure info. The data is a nice to have UNLESS you remove the film mid-roll. Then it is used to advance to the right exposure later when reloading it to the camera. Using a magnet on this could scramble the data.

[jumbleview]

Permanent magnet should not affect film. I have a 120 film frame (do not remember vendor) which uses small permanent magnets to lock two parts of frame together.

[BigMackCam]

The only caveat is for the defunct APS film format which uses magnetic media to hold exposure info. The data is a nice to have UNLESS you remove the film mid-roll. Then it is used to advance to the right exposure later when reloading it to the camera. Using a magnet on this could scramble the data.

Thanks, Brad The tool I'm developing - a film holder of sorts - is for 135 and 120 colour and B&W negative film, so this wouldn't be an issue... but it's still good to know, and an interesting advancement (albeit an unenduring one) in film history...

[Not a Number]

FWIW: The Lomography film holders use magnets to hold the parts together.

https://microsites.lomography.com/digitaliza/

[BigMackCam]

FWIW: The Lomography film holders use magnets to hold the parts together.

Yes, I've recently bought both the 135 and 120 versions of the Lomography Digitaliza. My question, although primarily related to the development of my own tool, also relates to my use of the Lomography products...

[Not a Number]

I don't think iron is used in modern films. I think it was used in some of the old plate processes in the beginning of photography. Although I suspect given the red color of some of the color development solutions there may be iron in so of the chemistry.

I don't see any cause for concern except for the above mention mag-stripes on APS film. I think the Kodak Disc cameras used mag-stripes as well.

[BigMackCam]

I don't think iron is used in modern films. I think it was used in some of the old plate processes in the beginning of photography. Although I suspect given the red color of some of the color development solutions there may be iron in so of the chemistry.

I don't see any cause for concern except for the above mention mag-stripes on APS film. I think the Kodak Disc cameras used mag-stripes as well.

Interesting. Many thanks for that! [I think Kodak Discs are comfortably outside my range of concern ]

[Kobayashi.K]

When you live in Europe, Conrad has a huge assortment of permanent magnets, round, bars, strips, and screwable.

[Alex645]

Can magnets have a detrimental effect on developed negative film, either B&W or colour?

Once upon a time motion picture film used a "mag stripe"; a strip for the audio track. There should be no effect of magnets on developed film.

[photoptimist]

As others have said, magnetic fields won't affect film.

My only word of caution with the design would be that if there is any roughness in the magnet surface or abrasive dust and the mechanism (or person) pulls the magnet in a way that makes it slide across the film before lifting off, then it could scratch the emulsion or base layer. Neodymium/rare earth magnets can be beastly strong and hard to separate and tend to slide first.

You might also take just a bit of care with iron and steel tidbits -- an errant staple that get sucked in and stuck to the magnet and then clamped to the film might not be pleasant.

I look forward to seeing BigMackCam Magno-Scan-O-Matic 3000 in operation!

[Digitalis]

I don't think iron is used in modern films.

A lot of red toners use Iron, or copper as it is significantly cheaper* than seleno/sulfite based gold toners**. And in any case even if the images were toned with iron there wouldn't be enough unbound elemental iron to only be weakly affected by magnets. In order to have any significant effect magnets need a ferromagnetic mass that is roughly equal to or greater than their own.

*Unlike gold, Iron and copper have a detrimental effect on the archival longevity of silver gelatin prints.
** gold chloride and sodium thiocyanate, look up Kodak GP-2. labelled as brown toner however if diluted properly, red tones dominate.