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NAB, and a scrim question

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Bob Cole
NAB, and a scrim question
on May 9, 2006 at 12:53:01 am

question #1:
Anybody see anything new and cool at NAB in the lighting area? I had a nice informative chat with some folks at Chimera, and also enjoyed trying out the Mole Biax 8. What a beauty -- though it may be a bit too much to handle, for my usually-short-handed shoots.

question #2:
The reason I wanted to check out the Biax is that I frequently encounter interview set-ups where I'd like to include a window. I know that Leo likes the Biax for that situation. I'm thinking about ways to scrim the background when it's just too bright. I've noticed that in stadium broadcasting booths, they frequently use black fiberglass screening material to knock down the background to a useable level. I need something that is as big as possible; cheap and durable are both nice qualities too. Do any of you folks use the window screen trick, or is there a good reason to avoid that?

Thanks.

-- Bob C


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cowcowcowcowcow
john sharaf
Re: NAB, and a scrim question
on May 9, 2006 at 1:25:17 am

Bob,

Dealing with windows (or sky) in the background is a difficult task. It usuallu requires a large scale treatment that costs money and time.

Obviously with the newer HD cameras that have "cine gamma" curves and other methods like the Varicam's Dynamic Level control it has become more doable, but one must still often resort to using a large daylight source (like an HMI light or a multitube daylite fluorescent), neutral density gel on the window, a stretched single net, or a combination of all the above.

JS


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Bob Cole
White and Black
on May 9, 2006 at 5:06:28 pm

Thank you John. This is really a new question but I wanted to thank you first for the answer to the first one.

I have a shoot coming up with a series of people against a pure white paper background. Is there a "gotcha" in my future, or will it be much like lighting against a chromakey?

On the other extreme... I have to shoot some tabletop sitting on a "pure black" background. I have done a bit of this so I know there is no such thing as pure black, but if someone has a tip I'd be grateful.

-- Bob C


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Frank Otto
Re: White and Black
on May 9, 2006 at 7:50:20 pm

White is a pain on many levels, Bob. I've shot a boat load of these in the late 70's to mid 80's - the era of talent on turntables and products being demonstrated in all white sets.

Just being "white" is going to play hell with the clip point. Then, the 5 stops or so span between "talent" and background. And, there's shadow - do you want em' or are you wanting the "limbo" look?

For most of my stuff (athletic clubs and cars mostly) I used from 1 to 4 "chicken coops" hung overhead and slightly forward of the subject. Occcasionally for cars, I'd use a white parachute hung from the grid and bounced a few 5ks off it. Rarely was the bg lit - when it was (for a seamless sky-ground background) I'd use a few sky pans - placed above the talent and focused ( if a broad light could be focused) just above the curve of the cove so the top and bottom of the bg just begin to fall out of light.

Backlight was, in reality, side light since I didn't want a defined ground shadow. Key light was for some, a nine-light punched thru a 12x12 silk, on others it was a Junior or Senior bounced off foam core, Occasionally, I'd pin a baby-baby to add eyelight or other highlights. Lots of separation - usually 10-to-20 feet from talent to bg.

The only tip I have for black bg is to crush the blacks a bit in the camera - 0 insted of 7ire.

There's a couple of other tricks depending on your look - black plexiglass for reflection, dusting velour with corn starch for an etherial, nebula look, even scattering copper and zinc oxide dust for a slight color variation (DISCLAIMER ! Kids don't try this at home without proper ventalation and preferably a mask - metalic dust can be toxic) For velour, I've also edge lit it to give a color cast - sometimes that's more work than it's worth because you end up having to cut light off the products.



Cheers,

Frank Otto



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Bob Cole
Re: White and Black
on May 9, 2006 at 9:49:03 pm

Thanks Frank. I will just be shooting one person at a time, not a car. The current "Get a Mac" ads are here at http://www.apple.com/getamac/ads.

I was worried about the clip point too -- thanks for the input.

-- Bob C


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Frank Otto
Re: White and Black
on May 10, 2006 at 2:19:40 am

Yeah, Bob...the biggest issues for me are always with the difference between talent and BG - some video DP/LD's light the BG and fill talent, others light the talent and wash the bg into the range prior to clipping. And there's the school of adjusting black levels after setting clip and (if you have a good video engineer)adjust knee and gammas. This is also the method we used in the extreme to shoot the rotoscope plates for Bakshi's "Wizards" to get a pure black and white shadowless image.

If you're doing the head-to-toe, I'd probably light the paper for a target video level of 88 ire and fill in the talent with a pair of large appature softs if I wanted an encompasing shadowless light - or only one source off side with a fill or kick if I wanted more modeling.



Cheers,

Frank Otto



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Bob Cole
Re: White and Black
on May 11, 2006 at 4:59:53 am

Thanks for the feedback Frank.

After looking at your posts I'm most concerned about clipping, in part because I don't really understand the problem. I've never (to my knowledge) actually had a shoot ruined by clipping, though I've shot blown-out windows aplenty. We will have a good (small) field monitor and tape playback so we can at least see what we're getting. And, our editing system clips overexposured video automatically. What is the real danger of clipping?

I have to confess I've never taken my waveform monitor to a shoot (or even turned it on for some time). But I will try it this time, and aim for 88 IRE on the background.

Thanks again for helping me with this.

-- Bob


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Frank Otto
Re: White and Black
on May 11, 2006 at 4:00:05 pm

My pleasure, Bob - and as always, I'd like to remind all that my views and techniques are just guidelines - the ol' YMMV is in effect. I tend to be conservative as an DP/LD - it's the video engineer in me.

In the broadcast world, clipping can cause buzz in the audio - due mostly to the hetrodyne scheme used by NTSC recievers. In the digital world, clipping can cause artifacts. In some cases the clipping can, in effect, put a compressor on the whites, and cause ringing, shadowing and artifacts around the non-white areas. Sometime the issue isn't raised until it gets compressed again from the post or distribution process.

RE 88 ire: Its a baseline - I start by holding the BG there and after I get a good balance between talent and BG. I usually set stops again until I get in the 92 ire range and let the mismatch that is everybody else's monitors work its magic.

As an aside, I always shoot commercial work and some interviews with a scope - its the equivalent of a multifunction light meter. I have a Hitachi VO-59 that I've had for just shy of 30 years - it's portable and dc powered. I know Tektronix makes an LCD scope and when mine finally dies I'll be getting the Tek.

Cheers,

Frank Otto



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Bob Cole
Re: White and Black
on May 14, 2006 at 10:42:35 pm

Thanks Frank. I made a test file in After Effects with pure white and various-sized objects.

The results were surprising -- no problems at all. I had heard some years ago that NTSC monitors tended to act like exposure meters, turning the aggregate of all the inputs into gray. I assume that was either a misunderstanding on my part, or things have improved.

-- Bob C


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