Gas station without pumps

2020 July 10

Ring light for iMac

Filed under: Circuits course — gasstationwithoutpumps @ 08:19
Tags: , , ,

I was having some trouble using the green-screen capabilities of OBS, and the videographer who works on online courses for UCSC suggested trying a ring light behind my iMac to get more light on my face. I decided to make a ring light and see if it helped.

On Wednesday I walked to my dentist appointment, rather than bicycling, so that I could stop by Palace Arts on the way home to pick up a piece of foam core to make a frame to tape to the back of the iMac, without blocking any ventilation ports.  I already had strips of LEDs that I could use to provide the light.

Here is the layout of the ring light, seen from the front, before mounting it on the iMac.

The hinge (made by scoring the foam core and then crushing the foam slightly at the score line) allows the monitor angle to still be adjusted, even with the foam core taped to both the stand and the back of the computer.

Here is the ring light attached to the back of the iMac with blue painter’s tape and lit up.

The ring light was not difficult to make, but it did not do what we had hoped. It does illuminate my face a bit more uniformly, but the camera in the iMac automatically compensates for the extra light, resulting in the green-screen background looking olive drab and being even harder for OBS to use in chroma keying. It’s too bad that OBS doesn’t have Zoom-like background elimination, which can handle a much wider variation in color and lighting of a green screen. The ring light also does not work well with glasses, as there are two really annoying reflections of the light off the front and back surfaces of my glasses.

So I wasted a day experimenting with the ring light. My next attempt at improving the green screen will be to mount a strip of LEDs at the bottom of the cloth screen, to see if I can erase some of the shadows there and get more uniform and brighter lighting of the screen.


  1. Kevin,
    I think if you put the monitor up on a stand so you look up a bit at it, first, better for you neck and back, but mostly according to selfie kids, its the best angle for a good looking image.
    Also, I think incandescent light temps of 2400-2700 make the best lookiing warm facial color light.
    An old client who did consulting for Marriotts had them change their bar lights from bluish to warmish and sales in the hotel bars went way up.
    We look better in warmer lights, in bar mirrors and in selfies.

    Comment by richard rebman — 2020 July 11 @ 14:14 | Reply

    • My camera is already somewhat above eye level, which is about where it should be. The iMac also seems to do color correction for the camera, so with the green screen behind me, my face comes out quite red, as the iMac tries to correct for what it thinks is a green-lit scene. I have to adjust the color back in the OBS software (and turn down the saturation), or I look like a British tourist in Spain.

      Michele prefers lighting around 2700K, but I prefer around 3000K, as the 2700K looks too yellow to me—it is, as you say, traditional for bars and restaurants to be dimly lit with yellow lighting, because the yellow light does hide age best. My ring light was cool white (3500K?), which is not the most flattering, because I happened to have 5m of cool-white LED strip at home. I also have a meter or two of 2700K LED strip, but I don’t think that the yellower light would have made much difference here—the problem was that the green screen was not bright enough relative to my face.

      Comment by gasstationwithoutpumps — 2020 July 11 @ 19:46 | Reply

  2. interesting. And clearly complicated.
    i know nothing about green screens or blue screens, but that is such interesting stuff.
    I was not thinking about hiding our age as we all look spectacularly good for our ages, but I was thinking about those old blue bar lights, (that was all in the days before LEDs), and people looked kind of like they had the flu or been on a long flight (in the blue or green bar lights) . And, being old….i was assuming LED bluish color as the early common ones were mostly like that.

    Comment by richard rebman — 2020 July 12 @ 12:25 | Reply

    • The LEDs I used for the ring light were cool white (so somewhat blue), because that is what I had the most of. I have given up on the ring light but added a row of LEDs along the bottom of the green screen to reduce the shadows there—it seems to help a little.

      Comment by gasstationwithoutpumps — 2020 July 12 @ 12:45 | Reply

  3. ah hah! a possible factor.
    Being old I can remember odwalla days here (no longer in buisiness–shocking and weird to me)… the late 70s/early 80s I shared a woodshop at the Sash Mill with a guy Willow who was the carrot juice maker in davenport for odwalla.
    And Willow was always short on rent, so would give us 3 gallon jugs of carrot juice overages to pay part of it.
    We lived on the stuff, felt great, and looked slightly orange.
    My neighbor in Felton, Denise, was shipping manager, and her girlfriend was a truck driver for them, then coca cola bought odwalla and immediately killed off the carrot juice and focused the whole buisiness on orange juice–maybe coca cola brass are really old guys who like screwdrivers? . Moved it all to Fresno i think, and now, it ends.
    I dont know, but now we say farewell to odwalla, which I dont understand at all. On balance, bolthouse carrot juice is quite tasty usually. Looking orange is not all that bad a thing,

    Comment by richard rebman — 2020 July 12 @ 13:31 | Reply

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