How Polycontrast filters affect Negative Film

[Apu]

This discussion got started in the Jobs forum and I'm shifting it here. I remember when I used to make b&w still prints in the lab, I used different grade polycontrast filters to get the desired contrast. The filter factor depended on the paper I was printing to and I remember usually using a number 3 filter. Correct me if I'm wrong but more contrasty images would yield from a higher number like a 5.

 

I'm just curious what would happen if one were to employ one of these polycontrast filters in front of a lens and shoot b&w negative. My colleague Dinko said it would make any yellow or magenta in the frame look whiter. Is this true? What would be the difference between a grade 3 and a grade 5? Would it affect any other wavelengths apart from yellow/magenta? Feel free to pitch if you have any thoughts anyone.

 

I cant think of any situation where one would need to employ these filters in this manner but if anyone has more knowledge, please enlighten us.

[John Pytlak RIP]

The way polycontrast filters work is that the KODAK POLYCONTRAST papers essentially have two different emulsion layers having different contrast, and sensitized to different parts of the spectrum (spectral peaks at 420 and 525 nanometers). The polycontrast filters are used to control the proportions of the high and low contrast emulsions that form the image:

 

http://www.kodak.com/global/en/professiona....4&lc=en#curves

 

 

Since B&W motion picture films do NOT have this dual contrast / dual spectral sensitivity response, you can't control contrast by using polycontrast filters. You can modify B&W developer time however to affect contrast/gamma.

[Apu]

Thanks Mr. P for that. Having spent some time reading through various forums, not just on this site, but on 2-pop.com also, I had a feeling you would be the first to respond. My warm regards :)