Wet plate collodion spectral sensitivity?

[Nodda Duma]

Wet plate was UV and blue sensitive.

Tell your friend to set up the lenses for FdC lines and then it’s simply a focal shift for the UV & blue spectrum. Performance will be the same with slight scaling of aberration magnitudes due to the wavelength. This is what the photographers understood as adjusting from visual focus to “chemical focus” I think was the term.

Or, he can use constant transmission from 330nm up to where it begins rolling off at 425 and ending at 500. However, some modern glasstypes that would substitute for glasstypes that are no longer available won’t pass the lower UV wavelengths...hence working at FdC. Pass that on and he should understand.

(I’ve done the same exercise as your friend by updating the pre-1900 designs on dioptrique.info to modern prescriptions in Zemax).

[goamules]

I thought that wet-plate era emulsions pretty much ortho; were sensitive to the blue-green end of the spectrum. Not sensitive to the red end or into the Ultra-Violet.

One could do some experimentation with B^W colored filters. A sort of contact printing set up could expose one plate to several colors from Red Green, Yellow and Blue. I am sure thart someone here can figure ourt a more sophisticated and more effective way way to do this in one shot.

I can tell you what you'd get if you use a yellow or amber filter on your lens! Nothing!

[ghostcount]

https://contrastique.blog/2012/04/22...ollodion-test/



Have your sitter wear UV lip balm for an interesting effect.

[Tin Can]

Thank you!

Now we have visual data

[goamules]

There used to be several good color chart wetplate studies, out on the net. Not sure if they still are, many of them were posted on the two wetplate forums that are now closed, CWreenactors and Collodion.com.

I like Contrastique and have shot wetplates with her in Paris. But this one is pretty dark and low contrast (ironically), there are better color chart shots out there.

[Tin Can]

We are late to the show, I will look at anything I can find

[pgk]

Thanks all, especially Nodda Duma (apparently very helpful). I have forwarded links and info and my friend is now looking at glass types with help from retired lens designers too. I think that he's actually quite intrigued by the way things were being done back in Victorian times. Having done some digital tests myself I'm actually quite surprised at quality and correction (especially chromatic) of some early lenses, although I cannot test very large format lenses as yet (working on it).

[goamules]

One color chart here http://www.paulalsop.com/wet-plate




Collodion spectral study here https://www.bordinphotographic.it/sp...-of-collodion/


Ostermans

[goamules]

With organics it will blow your mind trying to figure out what colors will show up as on the grey scale. Some yellow comes out light, some very dark, and it depends on the formula somewhat.

[Tin Can]

Thanks Garrett, those really are a visual aid!