Ilford Contrast Filter Spectra

Hi

Completely new here (ie photo.net), and it is not clear whether this thread still interests anybody .... Many years ago I was a spectroscopist and we used to model spectra as a linear combination of gaussian curves. A play with the Ilford data (for which my thanks to Ilford) shows that all those curves can be modelled pretty well as being the sum of 4 Gaussians ( at 432,512,530 and 568nM, subject to refinement). In differing proportions obviously!

I second approach is to use the data on the Olympus site, eg

Photomicrography - Color Compensating Filters - Magenta | Solutions Olympus pour les sciences de la vie

Which provides the transmittance data at 10nM intervals for a variety of enlarger filter settings. Interpolating/extrapolating to other settings should not be difficult.

Hope that helps Scott, both approaches are easier and more accurate than tracing the curves!

I second approach is to use the data on the Olympus site, eg

 

Photomicrography - Color Compensating Filters - Magenta | Solutions Olympus pour les sciences de la vie

That's exactly the same graph as Alan showed earlier.

And the OP hasn't checked back since August.

That's exactly the same graph as Alan showed earlier.

 

And the OP hasn't checked back since August.

That is absolutely right, but I wonder whether he had found the image from the same source (it has been copied many times across sites). This link also has the transmission data in tabular form (as per your suggestion).

But as you rightly point out, if he has not checked back since August, it is all pretty hypothetical!

I'm really not sure why Scottk wanted the transmission spectra. That was never revealed.

However, it strikes me that those data aren't of much use unless correlated with (a) the spectral sensitivity of the emulsion layers of the varigrade paper in question, or (b) the spectrum of the light source(s) of the printing system, or both.

The only graphs I've seen showing printing paper sensitivity curves have been quite crudely produced things that give little accurate information.

Maybe the OP wanted to construct a varigrade head using LEDs?

Maybe some other practical application?

Or maybe just a pointless academic exercise?

We'll probably never know.

I'm really not sure why Scottk wanted the transmission spectra. That was never revealed.

 

However, it strikes me that those data aren't of much use unless correlated with (a) the spectral sensitivity of the emulsion layers of the varigrade paper in question, or (b) the spectrum of the light source(s) of the printing system, or both.

 

(snip)

Often enough, I am interested in something just to know it, with no actual use.

I was told about 50 years ago by my grandfather, who used Varigam filters (and Varigam safelight)

that they worked with Polycontrast, too. Now that I have actual Polycontrast filters, I sometimes

use them with Ilford paper. I suspect that it could be a little different, but close enough for

most of us.

As you note, I suspect that light source color is important, and should be considered.

I presume people do that without knowing the filter spectrum, though.

Is the paper sensitivity spectrum available?

That's exactly the same graph as Alan showed earlier.

 

And the OP hasn't checked back since August.

Got side tracked by all sorts of things : ) Life happened.

My purpose is only academic. I want to visualize in my brain how enlarger contrast filters effect/compare with, paper sensitivity curves. The public darkroom I rent will not be open for at least another 3 months so unfortunately I'm back to thinking about other things then analog photography.

Thanks for all the interest/replies.