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[euswdwj]

This graph shows the spectral sensitivity for Efke KB50 film.



So far, I have only worked with orthochromatic film. Several questions come to mind.
1. Is it possible to work with this film under a normal darkroom red light?
2. How does the film response change the effect of red, yellow and orange filters?
3. Would red lips and rouge would come out black?

[t.r.sanford]

Many years ago, I played with Kodak "Tri-X Ortho." The difference of its spectral response from that of its panchromatic stablemate was noticeable but not dramatic, a matter of degree.

In the old days, darkroom workers used ruby lamps to develp orthochromatic films by inspection, but those were pretty slow films! If I were doing it, I'd think about turning the safelight on and off briefly to see how the image was forming -- not leave it on all the time. And I'd run some tests of the procedure first.

Depending on just how orthochromatic your material is, you can expect a red filter to work with a larger filter factor, perhaps substantially larger. And lips are rendered darker, but they don't go black.

[glennfromwy]

KB-50 is meant to be processed in total daarkness. To use a red safelight for even brief inspectin would be risky at best.

_________________
Glenn

"Wyoming - Where everybody is somebody else's weirdo"

[R_J]

1. Looking at your graph, there is a significant albeit attenuated response to the red wavelengths.

This would suggest that the film is not orthochromatic, and fogging will occur with any red light in the darkroom. In this respect, the film is very much panchromatic and needs to be handled in darkness.

2. With any contrast filter, red, orange or yellow, contrast is heightened by degrees in inverse order; red most and yellow less so.

3. There's a lot of resource on the net about colour filtration and effects on black and white film; generally, [Red filter + red
subject = relative lightening compared to the rest of the scene]. Red + Blue/Green (complementary colours) results in a darkening effect, perhaps what is termed "black" by some.

In answer to your question about red filtration and rouge: the film shows an attenuated spectral sensitivity/response to red, therefore exposure factor compensation must be applied (otherwise underexposure results).

It is unlikely that the rouge would be rendered black with red filtration if you are exposing accurately - if anything - rouge renders lighter in relation to the skin tones which may be rendered very undesirable through red filtration.

Standard convention uses yellow or green filtration for portraiture; the skin tones improve in relation to rouge, which darkens.

Hope that helps.