Ilford Contrast Filter Spectra

Discussion in 'Black and White' started by scottk, Jun 6, 2020.

  1. FWIW I just measured the RGB densities of a few of my old Kodak CP filters - kept in original cardboard sleeves and in the dark.

    None of them had the specified density to their complementary colour.

    The 50Y and 50M filters measured more like 35~40 (0.35 - 0.4D) to blue and green light, respectively. While the Cyan filters had all become near uselessly transparent. So beware of using Kodak CP filters. They haven't been made in some time, and even NOS ones are likely to have faded and be well out of specification.
    Last edited: Jun 11, 2020
    scottk likes this.
  2. Thanks for the reply. This is mostly over my head, but I'll read it again as I learn more.
  3. Great news, at least for me. Ilford just sent me a pdf showing the MG filter spectral sensitivities, just what I was looking for (they had been on virus lockdown). Attached here. Thanks for all the comments.

    MG Filter Set Scan 2015.jpg
  4. They still haven't provided you with the (linear) transmission spectra that you asked for, but instead the (logarithmic) density spectra.

    So now you've got to trace the density spectra from their graphs to extract the raw data, then apply a 10^x function and subtract that from a normalised 100% transmission.

    Thanks Ilford!
  5. Is there any thought that the filter sets for different VC papers aren't close enough,
    at least for ordinary darkroom work?

    For a long time, I used the Varigam filters that I inherited from my grandfather,
    who told me that they worked fine for Polycontrast. I now have some actual
    Polycontrast filters, and have used them with Multigrade.

    It is nice to have the actual curves, though maybe you should also get the sensitivity
    curves for the paper?

Share This Page