First step is to see what a UV filter does in terms of blocking UV. Then look at lens/cyanotype paper with and without the filter in front. And due to different kinds of glass each lens will likely be different. I'd also suggest keeping track of exposure time and if you live where I do, use a repeatable UV source not the sun.
Well, I don't think I will do it, because I don't have a UV source, but if someone does, they might want to give it a try.
Wet plate collodion was used to take spectra from individual stars as early as the 1870s. Henry Draper is usually given priority, with his spectrum of Vega in 1892, which showed what would today be considered UV lines.
Bare silver chloride is also most certainly exposed by UV light - it's how Johann Ritter discovered ultraviolet light in 1801.
Whether any of this has practical significance for wet plate photography is another matter, but early journals are full of discussions of the difference between actinic and visual focus, so I'd say yes, in general. UV-only or UV-rich illumination for taking photographs does not seem necessary, but that doesn't mean there are no effects - enhanced haze in alpine scenes, for example.
Oops. Spectrum of Vega in 1872.
1872 spectrometry! Amazing. It was several decades after that before a fairly firm theoretical basis for those lines was developed.
I'm also amazed that there was enough open time with collodion to get a bright enough image to collect.
One last thought, a couple summers ago I took a photo of my brother with an Ortho X-ray film and his skin in the photo was blotchy in a way that was not obvious to just look at him. I'm suspicious it was because of sunscreen and uv absorption.
Can't prove it. Was a huge projector lens with 2 or three inches of glass in the optical path.
Maybe some day I will deliberately test this notion.
Can you re-wet collodion plates with ether and alcohol they've dried out? Or does it come
Off the plate?
Fr. Mark: they did switch to dry plates as soon as they became available/known of. The speed increase was the major reason, but Vogel discovered dye sensitisers in 1873 and although it took another decade or so before good sensitisers were available for gelatin emulsions, there was a great deal if interest in the possibility of tuning spectral sensitivity among spectroscopists - astronomers and others.
Blue-sensitive emulsions show up skin damage much more clearly than red or IR responsive ones. Old scars and sunburn patterns show up nicely, even without a UV component. Some forensic photography uses near UV photography to show up bruising and other trauma which are not evident in a colour or red-sensitive B+W shot. Pure UV makes things even more dramatic:
https://www.youtube.com/watch?v=o9BqrSAHbTc
Easy way to check the influence of UV: grab the UV blocking gel from a set of printing filters and take one pic with, one without. There are more expensive solutions too :-)
Does a UV blocking gel (whatever that is) only block UV, with no effect on near UV violet? Someone else said that the proof UV affects collodion is that you can seen sunscreen, but I would not be surprised if sunscreen also blocks light in the near UV.
With regards to the sunscreen, you should check the effects under a violet coloured filter with your eyes, and then compare to the effect captured on your film.
But if you really want to test spectral sensitivity, then setting up an actual spectrometer pointing at something that emits an even and full spectrum light would be a rather good option. The equipment isn't that complex if you don't need super reliable accuracy and precision, and are just looking for a more ballpark kind of figure.
But you do have to remember to account for issues such as different lenses transmitting and absorbing different wavelengths of light, and it is one of the things that makes wide spectrum data collection 'interesting', as it can be awkward to calibrate if you have multiple lenses in use, and made more awkward if the lens happens to cause radical changes in focus for different ranges of non-visible light.
A project I worked on several years ago had multiple optics in play, and our telephoto lens let far less UV through than the wide angle lens we used, which made for some very confusing experiments due to a mix up in a spec sheet that had the wrong transmission values. Nothing like trying to figure out why the robot keeps missing target when pointing the second camera at things when no one has yet realized the second camera can't even actually see it.
Tim, the UV printing gels I had in my Ilfochrome/Cibachrome filter packs were fairly clear, with no real colour cast. Perhaps a tiny touch of yellow, which would suppress some near-UV blues and indigoes, but nothing I would call a tint.
I think A_Tabor is right, you're asking questions that can only really be answered once you are in possession of some spectra. Homemade UV-vis spectrometers can be quite good, but calibration can be an issue with unknown lens transmissions and grating reflectivities.
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