Yellow filter, anyone?

[jdanforth]

I have been thinking about spectral sensitivity of daguerreotypes lately and I had an idea. I thought that I could use a color correction filter to smooth out the response of the plates and to make the color rendition more like what we see. This led me to hypothesize that a yellowish filter might help in curtailing the blues (had to break out the ‘ole color wheel) but what to do about the UV spectrum?

It turns out that I’m about 100 years late to this party (as usual) and that the concept has been around for a while. The old orthochromatic films suffered from the same problem as our daguerreotype plates and, thus, the yellow filter was born. The K2 dye, in particular, was developed to remove blue AND UV from the image. Woohoo!

Curtailing the blues to match the deep reds seems like a good idea with daguerreotypes so I’m wondering if any of you have tried it. By cutting out the UV I’m hoping that it will remove some of the icky spotty effects that I see on skin tones.

[Jon Lewis]

I was under the impression that the sensitivity of daguerreotypes ended in the early greens somewhere around 520nm. Now I don’t think I have ever seen a spectral sensitivity curve of a daguerreotype so I can’t be sure but that’s around where the sensitivity of silver bromo-iodide ends. I’d expect it’s even shorter for Becquerel dags. If that is the case then a yellow filter would be about as effective as a lens cap. Some have used filters to just cut out the UV and it works but increases the exposure by a couple stops. But who knows, a yellow may work… I’m interested to hear what other people’s thoughts experiences are…

And I’m sure SOMEONE has spectral sensitivity curves for daguerreotypes. If you do, I’d love to see it! ” title=”Very Happy” />

[botticelli1972]

I have tried the opposite end of the scale, using a blue filter. My theory was that since they are only sensitive to UV/blue why not send only blue light to the plate. I did not do much with this as an 80A filter has a factor of nearly 3 stops which in Becquerel is a lifetime. In a somewhat subjective way I think the images were "better" but the extra long exposures were problematic.

jdanforth wrote:By cutting out the UV I’m hoping that it will remove some of the icky spotty effects that I see on skin tones.

This is the exact reason that Southworth & Hawes used/championed the "lighted Camera." The cause of the spotty effect is that the blemishes, scars and pimples on humans are usually red in color and thus show as black spots on a persons face on a finished plate. The white interior of their camera had a slight fogging effect that conceals these defects, they still show but are greatly softened. It also gives a somewhat soft focus look which is pleasing to many (softens wrinkles, ect). Check out the chapter on technique written by Mike Robinson in the recent book "Young America the Daguerreotypes of Southworth and Hawes" by Romer et all.

Larry Shutts

[jdanforth]

Well I ordered a yellow filter from B&H anyway. I was concerned about the loss of light but I’ll just have to deal with it. If I can possibly squeeze it in this weekend I’ll run an experiment shooting with and without the yellow filter. I’m not sure if pulling out the violet of the spectrum will be of any benefit now.

I’m interested that you tried the blue filter. That should subtract the orange from your images but at a considerable time cost. A green or a blue-green filter would ease the reds / red&orange from the image which would be of considerable benefit. Maybe I should have tried a green filter instead.

[jdanforth]

http://chestofbooks.com/arts/photograph … art-2.html

This is an interesting explanation of filtration on orthochromatic film that seems germane.

White clouds are much brighter to the eye than the blue sky, but if they are photographed on the film in the ordinary way the blue sky appears too light and the clouds are lost against it. In order to overcome this and to enable orthochromatic film to represent most of the colors in their correct tone values light filters are used which absorb the excess of blue light and prevent it from reaching the film.

These light filters are, of course, yellow in color, since yellow absorbs blue light and thus, by the use of yellow light filters, which are sometimes called color screens, the excess of blue light can be absorbed and a much improved rendering of sky and clouds can be obtained.

They say yellow but I hypothesize that the best result for getting tonally accurate dags would be a yellow-orange filter. This would help with skin complexion, the Red Barn problem, etc. That is, of course, assuming that you can live with the extra stops!

[Jon Lewis]

When I shoot panchromatic film I often use a red filter to make the blue sky a nice velvety black and give good contrast to the clouds. If you can get the yellow filter to work with the limited sensitivity I’ll be very excited but I remain quite skeptical ” title=”Wink” />

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