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Lighting lecturer during PowerPoint presentation


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#1 Jack Kelly

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Posted 29 October 2008 - 07:52 AM

I'm due to video a lecture soon and I'm eager to get any advice at all! I've filmed a few lectures before but I've never been entirely happy with the lighting so I'd like to try upping the game a little this time.

The venue is a large meeting room (i.e. there isn't a "stage"). There will be a front-projected PowerPoint presentation shown on a screen on the front wall. The presenter will be free to walk the width of the room, including in front of the projected image (i.e. it's entirely possible that they will spend some time illuminated by the projector).

I'm very limited in where I can position lights because my lights mustn't spill onto the projection screen. Neither must my lights distract the audience or the lecturer.

Ideally I'd like to illuminate the lecturer to a level similar to the level to which the projector will illuminate the lecturer if they stand in the projector's light (i.e. I'd like to fix the exposure and I don't want the image to clip horribly if the lecturer stands in front of the projector).

My current plan is to use two KinoFlos: one to each side of the front wall pointing directly towards the lecturer (i.e. if the lecturer was standing in the middle of the front wall facing towards the audience then he will be illuminated on both sides of his face by the two KinoFlo units). There are several reasons why I'm thinking of using this setup:

  • I want to use large, soft sources to illuminate the lecturers
  • I like the idea of using lights which wont run hot for two reason: a) safety and b) we'll have the aircon off for sound and it will get hot in there if we run bit tungstens or HMIs.
  • It should be relatively easy to use the doors on the kinos to prevent the light from spilling onto the projection screen or from blinding the audience too much

My biggest concern about this setup is that the level of illumination on the lecturer's face will change quite dramatically if the lecturer moves around a lot. One possibility I'm considering is building my own "Kinos" using high-frequency dimmable ballasts and I'd control the light levels on the two "kinos" from my camera position.

I'm shooting on a DVX100a in 16:9.

Any thoughts would be great!

Many thanks,
Jack
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#2 Jack Kelly

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Posted 03 November 2008 - 12:14 PM

Here's a schematic diagram of my planned setup:

Posted Image

All 3 lights will be a fairly low-power fluorescent fixtures. Light3 will only provide a tiny bit of fill and shouldn't overtly affect the blacks on the projection screen (the room will be fairly brightly illuminated throughout the entire session as it's more of a workshop than a traditional lecture).

Please do let me know if you have any better ideas or if you can spot any particularly stupid elements of my plan!

Many thanks,
Jack
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#3 Ken Zukin

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Posted 03 November 2008 - 12:59 PM

Hi Dan aka Jack,

Well you seem to have a pretty good handle on things. In my experience, it's better to request that the speaker stay on one side of the venue, and light them from the other side. Psychologically, it then looks as though they are being illuminated from the screen, which looks "motivated." If this isn't possible (if the lecturer insists on "working the room"), then your two key light set up is OK. Generally though, one key light is best (there is only one sun). If you do use two lights, try to make one twice as bright as the other.

Also, your power-point projector will most likely be pumping out daylight balanced light, so make sure you lamp your kinos with daylight bulbs. If it were me, I would use an HMI, as they don't run that hot. The room itself looks pretty small, so a 400w HMI, or even a color-corrected 1K tungsten fresnel may be preferable. The problem with fluorescent fixtures is that they aren't very punchy; they spread light all over the place. With a fresnel, or an HMI par, it's a much easier job of focusing the beam where you want it.

You may want to tell the talent that if they spend a lot of time in the beam of the projector, they'll basically look like crap. Appealing to their vanity can work wonders.
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#4 Jack Kelly

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Posted 10 November 2008 - 07:38 AM

Dear Ken,

Many thanks for the reply. Good point, I should look into hiring an HMI or two for the day. Thank you.

Thanks again,
Jack
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#5 Andrew Koch

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Posted 10 November 2008 - 06:25 PM

You need to change your username to your full first and last name as per forum rules. Do this by going to "my controls" at the top of the page
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#6 Jack Kelly

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Posted 11 November 2008 - 04:24 AM

OK!
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#7 Jerry McKimm

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Posted 06 December 2008 - 11:45 PM

Jack,

It has been nearly a month since your last post about your presentation. I am curious if you did the presentation and if so, how you decided to light it...and how well it worked or didn't. In the future I would like to light some presentations and am looking for ideas.

Thanks,

Jerry
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#8 Jack Kelly

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Posted 07 December 2008 - 06:46 AM

Dear Jerry,

I was fairly pleased with the results. I used a lighting setup something similar to my diagram above except I didn't put a light at the back (i.e. I used two 5400K fluorescent fixtures, one to either side of the presenter). I'm glad I used fluorescent fixtures instead of tungsten lights for several reasons:

1) I don't think the presenters would have liked the heat and harsh light produced by direct illumination by tungsten film lights
2) The fluoros didn't heat the room too much (The air con was off for sound, of course)
3) I was very pleased with the soft illumination created by the fluoros.

Before the event, I had established that the projector had a colour temperature of about 6400K. I decided to try to light the presenters with 5400K light to try to match the projector reasonably closely, and also because the conference room had windows all along one wall which would let in some daylight (which I would not have been able to gel). I used 5400K fluoros to light the presenters. The venue had 3200K house-lamps built into the ceiling in rows extending from the front to the back. I put full-CTB gel on the front row of 3200K house lamps built into the ceiling (these lights were just to the front of where the presenters were and so threw a fair amount of light onto the presenters). This worked quite well.

However, my colour-temperature decisions did have two negatives:

1) From the perspective of the audience members in the conference room (who were lit with uncorrected 3200K light), the "stage" of the room was bathed in a cool, quite unflattering light (because if you sit in the audience (with 3200K light above you) then your eyes calibrate for 3200K and hence the 5400K light illuminating the presenters looks cold and harsh)

2) Some of the uncorrected 3200K light from the middle of the room did find its way onto the presenter's faces, giving them a slightly strange (but perhaps slightly flattering) orange tint.

To be honest, I think it may have been better to light the presenters with 3200K lights, put a camera filter in front of the projector to bring the projector's colour temp down to 3200K and gelled the front windows with CTO (there were no curtains). This would have been easier (it took a while to gel the lights) and it would also have meant that the entire room would have been lit with 3200K.

Also, next time I think I'll try to impose stricter rules on where the presenter can/can't move. One of the presenters had a really irritating habit of pacing up and down whilst presenting!

Anyway, the client was happy so overall it was a success, I suppose. But it was by no means perfect.
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