Color film developed as BW....is it Ortho?

[Ambro51]

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Having started developing very old rolls of my forgotten film, I found D76 does a good job of recovering images.   As the silver emulsion is bromide based, is it a true orthochromatic film?   

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[giannis]

On 3/30/2020 at 4:25 PM, Ambro51 said:

Having started developing very old rolls of my forgotten film, I found D76 does a good job of recovering images.   As the silver emulsion is bromide based, is it a true orthochromatic film?   

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Of course not. If it was orthochromatic, red would appear as almost black. There haven't been any orthochromatic colour films.

The reason why you see messed up contrast, fog and tonality,  because of:

1. the blue blocking layer ("yellow mask") that sits below the blue sensitive emulsion layer,  and above the green sensitive and red sensitive layers. This blocking layer is made of colloidal silver, that during normal C-41 processing gets bleached and washed out with the rest of the silver (the colour sensitive layers), leaving only the colour dyes on the film. If you develop as B&W, this silver doesn't get washed out (if you bleached a B&W negative you'd end up with a blank film), and gets developed instead, adding density (fog) and lowering contrast.

2. the orange mask of colour negative films, which also adds density and lowers the contrast