Into the blue
In a previous post, I tried to explain how a latent image is formed during the exposure of a collodion wet plate. Now, let’s talk about what light collodion sees and what brings the special look to collodion wetplate photographs.
The visible spectrum
The wavelengths of light, that humans can perceive, is part of the electromagnetic spectrum and reach from 450 to 700nm. While light with 700nm wavelength has a red color, the other end of the visible spectrum, around 400-450nm is blue light. Our eyes also have a maximum sensitivity and this is green light - not really surprising since all nature around us is pretty much green.
Color film and digital sensors try to match the color sensitivity of the human eye to get the best reproduction of the environment, while black and white film material only renders lights and shadows of a scenery. Of course, there are different types of black and white film that are sensitive to a specific color ranges for example to enhance contrast.
Collodion wetplates are special in their sensitivity: they mostly are sensitive for blue and ultra-violet light and blind for mostly green, red and orange light. One might call this orthochromatic.
Blue and ultra-violet
The sensitivity range of collodion wetplate is a narrow one and the process was not optimized to render contrasts like humans see. Moreover, it worked to produce an image and that was fine for several decades in the 19th century.
Sliding down the color rainbow from UV to blue light and coming to green, collodion is loosing most of its sensitivity. There are some collodion formulas, that claim to be sensitive to green light, or even have some sensitivity in this color, but this hasn’t been proven yet. It might be a very interesting study though, so if anyone reading this have optical devices to output colored light (also UV), please contact me.
It is proven, that collodion doesn’t see orange to red light, since our darkrooms can be illuminated with orange and red safelights.
Always test your LED safelights if they really are safe for collodion! Coat a plate, put it into the silver bath and sensitize. After sensitizing leave it open in your darkroom / darkbox for about 5-10min, then develop and fix the plate. It should be clear, no fog etc. If you have fog, probably your light is not suitable or your chemicals need some maintenance.
Lenses and lens coatings
Having mentioned, that collodion is most sensitive in the blue and UV range, one might come to conclusion that coatings of modern lenses are not very “good“ when shooting with collodion. I have experienced, that modern coated lenses deliver a very hard contrast and in my opinion, I don’t like the look modern, coated lenses have with collodion. Additionally, coated lenses are 1 to 2 stops slower than uncoated lenses.
If you are a in a studio doing portraits, maybe with strobes, you won’t recognize much difference, because your strobes are not emitting UV light if they are not modified. As soon as you want to pour plates outdoors in natural light, you will soon get an idea that uncoated lenses have a better contrast range especially in the midtones while being much faster.
Conclusion: collodion wetplate is perfect for outdoor photography
Since about 3-4 years, I am working a lot outside of my studio. This is, of course, exhausting and I always have to take many boxes of equipment with me, but it always is worth the effort.
Collodion wetplates offers artists a complete different view on our outside world: being sensitive to only a specific spectrum that we also see (blue) but also being sensitive to a light, that is not visible for us. This gaze is unique, this gaze can’t be copied and it is beautiful.
Sehr gut, danke dir:)