Studio Lighting Question

Discussion in 'Beyond the Basics' started by smoke665, Mar 13, 2018.

  1. smoke665

    smoke665 TPF Supporters Supporting Member

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    Thanks Dave, maybe I wasn't hearing things after all. LOL


     
  2. Derrel

    Derrel Mr. Rain Cloud

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    I've been a Brown Line user since 1986, and a Black Line user since 2001 I guess it is. One thing, in Brown Line, if you use Asymmetrical power distribution, you can use the #3 and #4 outlets on the subject at their lower power distribution, and the#1 and #2 outlets on the background, and their higher power output, and can easily key-shift gray seamless paper up to pure white. On the D402 pack, that would be a 4-to-1 power distribution, with three (one light at 200 W-s and the other two at 50- and 50-), or with four lights (120- and 120-, and 30- and 30- Watt-seconds).

    Key-shifting was a big thing I learned from Dean Collins videos back in the day. It's wayyyyyyy easier to make a white background by using _LESS_ light on the subject, and opening the lens aperture up, and thus making the background nice and white, as opposed to having to blast a metric ****-tonne of light all over the shooting area. D402 power options.jpg
     
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  3. smoke665

    smoke665 TPF Supporters Supporting Member

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    @Derrel in the video he talks about the ability to "increase" both the saturation and vibrancy of gels on the background, by adjusting the light + or -. Am I missing something, because as this is global adjustment it seems as if you would either dilute the gel color or darken it?
     
  4. Derrel

    Derrel Mr. Rain Cloud

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    Yes....by decreasing the amount of light shot through the gel, that will "darken" the background's gel-color, and so the color will become more-saturated. If one blasts more light through a colored gel, it will cause a more-pastel, and less-saturated, less-vibrant-appearing color.

    The background light level is its own thing; the subject light level is its own thing.

    The way the background is rendered depends on the difference in f/stop value, measured by reflected light metering, from the exposure used for the subject. There is no "global" adjustment being done...the background is lit one way, the subject is lighted another way.
    **********************

    Because of the way this works, we can pre-determine exactly HOW dense/dark/saturated a background will be, by measuring the difference in a background reflective meter reading taken from the camera's distance/position as compared against the incident light meter reading's f/stop value as metered at the subject's face distance. We can determine the background's color, by meter reading, with perfect precision and certainty, no matter if the background paper is hitting a white seamless, a gray seamless, or a black seamless! *

    *****
    Explaining the asterisk above! RE: determining the background's density/darkness/saturation:

    Because the ___difference__ in f/stop is measured by a reflected light meter reading taken from the backdrop, and that reflected reading is taken from the camera position and distance, and we are measuring the amount of difference between the subject's light level as metered by an incident light meter held at their face, and we have set the lens to THAT f/stop---to determine the density/hue/value/saturation of the background, we need to calculate the amount of difference in f/stops between the subject's exposure f/stop, and the background's amount of reflected light that reflects back and hits the sensor or film, as measured from camera distance.

    We are determining and setting the actual f/stop on the lens for the main light on the subject, by using an incident reading held at their face. However, it is possible to KNOW, precisely, the amount of difference between the subject's exposure value, and the amount of light that reflects from the background material and which bounces back to the sensor.

    No matter if the background material is white paper, or if it is gray paper, or if it is black velvet, the amount of differential determines the background rendering. Depending on the reflective value of the material the background is made of (white,gray,or black paper)--we need to ADJUST the light on the background, to create the final background's density/tone/color hue.

    Does this make sense? I've punctuated that as well as I can. Let me add this though:

    If you set the lens to f/16 and light a woman from 10 feet with a light, then shine a second light onto a white wall, a gray wall, and a black wall, all three backgrounds will have different final background densities, right?

    There is a simple way to measure the subject's light value, and set the lens to that f/stop.Use an incident meter, and meter the main and fill light,and set that f/stop on the lens. And then, measure the amount of light that hits the background and makes it back to the camera, using a reflected light meter reading from the camera distance, and thus we can KNOW, exactly, if the amount of light we allow to hit the backdrop, will deliver to us one of the following: 1) a white backdrop or 2) a gray backdrop or 3) a black backdrop.

    By keeping the subject light level the same, and keeping the f/stop set to the right value FOR THE light that hits our SUBJECT, we can adjust the background light power, either up or down, to vary the background's density or value.
     
    Last edited: Mar 13, 2018
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  5. mrca

    mrca No longer a newbie, moving up!

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    Darrel, I just joined this site last week and it is great to see someone here is a fan of Dean Collins. I have my chromazones chart printed for all my gels. From my stool, I can adjust the bg from pure white, to light gray, to dark gray, kill the bg lights and turn on the kickers and go to a black bg. As for the question on increasing the light through the gels lightening the bg color, think adding water to a bucket of paint, it lightens the color. And you do need a meter with reflective capability to measure strobes on the bg. Mine is always in my right vest pocket. For those folks that don't think they need a meter, wait til you want to get in another setup and only have 3 or 4 minutes or are setting up and are told you only have the dreaded 5 minutes. Try chimping 3 or 4 lights in that time. I stand at the subject, fire, meter and adjust the lights and take an exposure reading and am back at camera shooting. I'd hate to miss the shot of the day because I was screwing around shooting and chimping endlessly. Besides, do you think that looks professional to your client? Would you hire a carpenter to build your house who didn't use a tape measure? It can be done but should it? It also lacks the precision and repeatability of using a meter. I get the exact 2 shades of gray I like and precisely the brightness of pure white I want. That is important as it minimizes or eliminates too much light reflecting off the background and wrapping around my subject.
     
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  6. smoke665

    smoke665 TPF Supporters Supporting Member

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    I quickly found that the amount of time spent doing this increased exponentially as the number of lights involved increased. Best decision I ever made was getting a meter.
     
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  7. Derrel

    Derrel Mr. Rain Cloud

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    Glad to see you on here, mrca. You're experienced and knowledgeable. I've only seen a few of your posts but I can tell you know what you're talking about. Yeah there's nothing like a flash meter. I'm partial to Minolta flash meters, but have been thinking about going with a newer Sekonic.
     
  8. mrca

    mrca No longer a newbie, moving up!

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    I use sekonics and have an L-558 incident/reflective for sale. Thank you for the kind words. Before relocating cross country, I was in charge of the mentor program for the Professional Photographers of America in northern CA where I lived. Have won and judged professional competitions. It's great to see someone like you here who appreciates the craft.
     
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