Questions about lighting for wet plate photo (studio portrait)

Discussion in 'Black and White' started by 10990877, Dec 9, 2021.

  1. Hi. I am new to wet plate photography. I am hoping to get some advice about how to make studio portraits using artificial light.
    I’ve understood that collodion is sensitive to blue/green wavelengths but not so much to yellow/red wavelengths, and some say that strobes and LED lights are not effective for wet plate photography.

    Here are my questions:
    1)I have Profoto Acute2 2400. Would this be too weak?
    2)Another light I have is Yongnuo YN-900 LED Video Light(900 LEDs, 5500K) . If I use a blue filter over the light would that help?

    Any tips or technical advice is greatly appreciated!
  2. Not all "wet plate" is equal. You've got to figure out what effective ISO your plate has, then figure out how many "foot-candles" of light are needed.
    I'd google around for instructions on coating the plate, and then figure out exposure from what you've started with.

    By the way, these days pretty much anybody is "new" to this, ;)
    10990877 likes this.
  3. Collodion emulsion isn't sensitive to the yellow to red end of the spectrum at all.

    A blue filter won't help. Filters subtract light, not add it.

    'Daylight' white LEDs are quite high in blue and violet light, but most of the commercial panel type lights are not very powerful. You really need something with an output of several thousand lumens to keep exposures from running into tens of seconds. Domestic 100w-equivalent LED lamps put out around 850 lumens each. So maybe a bank of 10 or more of those would give sufficient light. They'd certainly be cheaper than those overpriced and underpowered video panels.

    Strobes also have quite a high blue/UV output - especially the cheap ones without coated tubes that reduce UV light.

    I've no idea why "some say that strobes and LED lights are not effective". They have a far bluer spectrum than any alternative, apart from an arc lamp or daylight.

    However, most of the early portrait studios were constructed to use daylight; having large skylights and picture windows. Some were simply open stage sets built outdoors to give the appearance of an interior scene.

    FWIW. My first lighting setup consisted of a large beauty dish equipped with a 1000 watt tungsten bulb, plus some 500w floods. It was totally inadequate in power with 100 ISO colour film for shorter exposures than around 1/15th second. So good luck with your single-figure ISO wet collodion plates.

    And you can buy perfectly good sheet film 'off the shelf' now you know! Because using an antiquated technique won't get you 'old fashioned' looking pictures, if that's what you're after.
    10990877 likes this.
  4. Thanks for your replies! Now I understand that placing a blue gel on the light won't contribute to the formation of images. I guess I need to find a more powerful strobe or try to come up with some other ideas shooting outside.
  5. I know s*** about collodion, besides an URGENT(!) reminder that it can go "boom"... Double check your liability / building owner insurances, put window replacing company on short dial, check weather forecast. - Seriously: Germany banned New Years Eve fireworks once again, to let hospitals focus on COVID, so it is maybe not the best time to blow up one's darkroom? (Lensrentals' Roger blogged about blowing out school windows as a teen.)
    Given a choice, I 'd rather prep plates in a tent and shoot them outdoors, assuming my sewing machine is enough to clear up a worst case's mess there.

    Your strobe: Arrange a test subject in a dim studio, load a plate and pull your dark slide out bit by bit, to expose 64 to 1 pop of your flash. Evaluate and shop flash power accordingly.
    I dare to assume that your plates might be UV sensitive too and anything suitable to light a portrait, like the UV lamps used in offset plate contact copying frames, would be causing eye damage to the subject.

    As Rodeo Joe mentioned: Sheet film should be easier to expose. If you want it only blue sensitive, buy x-ray film.
    10990877 likes this.
  6. Indeed.
    I assume you already know that the preparation of collodion involves dissolving gun cotton in ether. Not a task to be undertaken lightly, nor in a less than well-ventilated area.

    And, depending where you live, you might have difficulty purchasing the ingredients, and possibly need a license to use them.
  7. No need to be afraid of Wet Plate photography. Won't go boom etc. And Bostick & Sullivan in Santa Fe can supply all your chemicals. They also may have good advice.
  8. Seems to me that there are two things to consider in a photographic process.

    First is the light sensitive compound, and second is what holds it. These two developed (ha ha)
    more or less simultaneously.

    But okay, the traditional collodion has AgNO3 in solution and adds KI, forming AgI.
    Seems to me that you could use KBr instead, for AgBr, maybe more sensitive.

    With a little, or maybe a lot, more work, you could add sensitizing dyes.

    The main disadvantage of collodion is that once it dries, wet chemistry doesn't
    go into it. That is why it needs to be developed before it dries, and then was the advantage of gelatin.

    But also, as well as I know it, there are some ions that are used in low concentration that make
    our films now much more sensitive. Those also weren't known at the time, but might be used today.

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