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Cave Lighting and High Definition


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#1 Teddy Todd

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Posted 13 June 2005 - 07:52 PM

Greetings everyone,

I'm new to this forum, but have already enjoyed the great discussions going on here. It is incredibly helpful to have such a large group of knowledgeable professionals talking film in one place. The internet rocks. I would appreciate any help you guys can offer to my questions below.

Next month I'll be shooting a film which is largely set in a cave. We've built sets for most of the cave shoot, but we will also take a few shots in an actual cave as well. We are shooting on the Panasonic Varicam with the Pro35 adaptor and Zeiss Super Speed Primes. We will also have an HD zoom, and probably an Angenieux 35mm zoom available as well.

About half of the cave action takes place in an area that can have some low level fill light, as in the story there are lights from a previous expedition strung about the area. However, the other half of the cave stuff takes place in a completely "virgin" area of cave that obviously has no lights except what the caver(s) bring with them. These will include flashlights, glow sticks, and later, flares.

I want these scenes to look very dark, like the characters are actually carrying the only sources of light, and something could be right next to them and they wouldn't know it unless they pointed their light right at it. I will try to get a slight fill on the faces of those carrying flashglights, as if it is a bit of backspill or something from their lights. But other than that - dark.

A few questions now:

1. What kinds of flashlights should I use for this purpose? I know the Pro35 adapter will eat up an extra two stops or so of light, and I do want to see the areas where they are pointing their lights as well as a bit of the flashlight carrier as well. Any ideas or suggestions?

2. I'll obviously have to have many shots of the flashlights themselves(not the beam) overexposed. I know this is a no-no in a video format like High Definition. Is this going to be too objectionable for us? Anything I can do to make these large overexposures look better on this video format? How bad could these overexposures be on the Varicam's HD?

3. What would be good ways to light these areas to look as if the light is coming from a flashlight, a glow stick, and a flare in otherwise pitch dark?

Any pitfalls or other issues I should be aware of to guard against a bad result or to exploit for a good one?

Thank you very much for your time. I'm especially concerned about #2, the overexposure issue, as I don't want it to look terrible on the HD video.

Thank you,

Teddy
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#2 Landon D. Parks

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Posted 13 June 2005 - 08:27 PM

As a Caver (aka: Cave Explorer) myself, I feel like I know a little about this. I have helped out on several cave documentaries....


I'm especially concerned about #2, the overexposure issue, as I don't want it to look terrible on the HD video.

What kind of film is this? Will any of it be shot in Chroma? or is it all Sets / real locations?

I'm interested to know the story of this cave film, if thats ok with you... I find films about caves very facinating and I'm just wondering what your story is about...


Any pitfalls or other issues I should be aware of to guard against a bad result or to exploit for a good one?

From someone who has shot in caves for several years, I can offer this avice: When your filming in the REAL cave, you have several thing going against you... mainly space... and also if your to far down, you need to find some way to get electric there, rather through extension cords or Batteries... Your crew will also hate you for draging them through the mud... My advice is get REAL cavers to go with you on the REAL cave shots, many cavers have done videos in caves before, and know more of what there doing than non-cavers attempting to make a video in a cave.

Oh and I almost forgot to say: LIGHT! Caves are 40x darker than the night sky, so by nature you need 40x more light than you would to film outside. You also have to be real carfule how you film the cave, cause your gonna have limited space and a lot of lights... and if your dealing with HD a fairly big crew...

on a happy note however: If your gonna film both in and out of a real cave, my advice is just film the whole thing inside a BIG loft cave with a lot of features, this way you dont have to spend tones to re-create what is already there by nature...

Just my amature advice...
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#3 anamexis

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Posted 13 June 2005 - 08:32 PM

Caves are 40x darker than the night sky, so by nature you need 40x more light than you would to film outside.

<{POST_SNAPBACK}>


Um, I don't think that's exactly how it works.
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#4 Landon D. Parks

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Posted 13 June 2005 - 08:37 PM

Well, maybe not... but still, It's a good representation of what Im trying to get across... Take it from me, I'v helped on more than 8 cave videos in the last 3 years, and every single shoot we always bring tons of light, more than what you think you would ever need... and when you get down there, you find you still dont have enough lights.

It all depends on the size of the cave, if your lighting a small crawlway then you will need VERY little light, but your filming the big room in carlsbad caverns, you'd better have more than a DP kit! and dont count on the lights that are already in some caves, they don't work out for filming... In fact, they get in the way..

You get my point...
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#5 David Mullen ASC

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Posted 13 June 2005 - 10:43 PM

Well, considering he wants it to look DARK, then he shouldn't have any trouble accomplishing that...

It's OK for flashlight beams to be bright and clipped in HD -- you don't really expect to see the filament in the bulb anyway. In a very tight insert though, you'll probably stop down a little (obviously this being video, you can see the results on the monitor and make an immediate exposure adjustment.)

I'd probably use Surefire or Streamlight flashlights, unless you want to throw a beam across of huge space, then maybe those big Xenon units.

Some smoke would help create separation and see the beams.

You can use white or silver cards (like Roscoflex material) to catch a flashlight beam and bounce it back into the faces.

You still might want to consider sketching some of the rocks with a little raking light in the wide shots so it isn't too pitch black in there.
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#6 Alvin Pingol

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Posted 13 June 2005 - 11:03 PM

2.  I'll obviously have to have many shots of the flashlights themselves(not the beam) overexposed.  I know this is a no-no in a video format like High Definition.  Is this going to be too objectionable for us?

<{POST_SNAPBACK}>


I wouldn't worry too much about this. To the viewer, the flashlight represents the one and only source of light, that which illuminates the otherwise pitch black surroundings. Naturally, the contrast ratio between the flashlight face and dark surroundings would be very high; having the face of the flashlight blown out should look natural. Moreover, the face of the flashlight can't possibly occupy more than a small fraction of the frame at any given time, so a small hotspot should not be objectionable. Plus, it's not like you're losing valuable information in the highlight; people don't need to see the bulb.

I would worry more if you try to keep too much detail by stopping down and using supplemental lighting - makes it seem as if the guy's flashlight isn't bright enough!
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#7 Teddy Todd

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Posted 14 June 2005 - 01:15 PM

Guys,

Thanks very much for the suggestions. They are very helpful.

Next movie I hope I can afford to hire one of you two!

http://www.knivesand...ct/surefire.htm

Is there a flashlight in this bunch that you might recommend for use on this project?

The biggest room is 25 X 15, but it doesn't need to be seen all at once - just in an arcing beam as he points the light around.

Also, what would you try out for the glowsticks and flares, in terms of augmenting the light coming from those practical sources?

Landon - I'll talk to the Producers today and make sure I can spill about the plot - they've been pretty tight-lipped and I want to make sure. I can tell you it's based on a well known caving story.

Thanks again for the replies guys.
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#8 Landon D. Parks

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Posted 15 June 2005 - 02:44 AM

Landon - I'll talk to the Producers today and make sure I can spill about the plot - they've been pretty tight-lipped and I want to make sure. I can tell you it's based on a well known caving story.

Well, I don't recall and "Big" stories, at least here lately... I think the biggest story is when I was called @ 3:10am one morning by the area cave rescue person and was told they needed help in pulling a man from a cave, where he had sliped and fell from a pit about 25 foot. I arrive and come to find out its only me and 3 others... now THAT is a big story! :huh: movie material I'm sure!

PS) After 12 hours of working at it, we finally pulled him out with a both legs broken and several ribs broken. Moral of the story: If your drunk, dont go caving (Be sure your crew knows this!) As crews on low-budgets usually drink to escape the torture of the sets...

Edited by Landon D. Parks, 15 June 2005 - 02:46 AM.

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#9 Brian Wells

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Posted 15 June 2005 - 04:32 AM

2.  I'll obviously have to have many shots of the flashlights themselves(not the beam) overexposed.  I know this is a no-no in a video format like High Definition.  Is this going to be too objectionable for us?  Anything I can do to make these large overexposures look better on this video format?  How bad could these overexposures be on the Varicam's HD?

Varicam is 640ASA so you should be good with the low light situation--perhaps using only flashlights if that is the look you want. With a low contrast setup file, you should have a ten stop latitude available. I'd say you could get a very nice "Flared Glow" from the flashlights using a Varicam whereas other video cameras would burn out to "Ugly Digital White" much sooner. If it's still looking a bit scruffy on Varicam, you could (under)expose for the highlights as to maintain detail. Try using "zebras" to evaluate exposure. (If you do expose for highlights, shadows could be brought up to a reasonable level in post without appreciable quality loss.)

Landon--Spelunking is fun isn't it? Some of my relatives are in Orange County, Indiana and our family has two caves on a farm. One is safe and one is not. I've been in the safe one and boy, I'll agree with you: caving is a blast. Glad to hear you enjoy it as well!
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#10 Sam Wells

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Posted 15 June 2005 - 12:38 PM

Why not loose the P&S and go with Digi-primes for this ?

-Sam
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#11 Alvin Pingol

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Posted 17 June 2005 - 12:19 AM

Also, what would you try out for the glowsticks and flares, in terms of augmenting the light coming from those practical sources?

<{POST_SNAPBACK}>


Something slightly diffused (and appropriately gelled) for augmenting the glowstick, and a harder source for the flare.

I can't offer specific recommendations, but just be sure that whatever you're using to augment these sources doesn't create a shadow of the practical! After all, a lightsource will never cast a shadow of itself. ;)

>>Why not loose the P&S and go with Digi-primes for this ?

I second this recommendation. Not only will it allow you to work with lower light levels, but will be of great benefit when you wont have to worry about toying with the device when in tight quarters underground.
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#12 Teddy Todd

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Posted 18 June 2005 - 11:00 AM

Thanks for the recommendations guys.

In terms of Digiprimes. We are going with the Pro35 adapter because we feel it will offer us more options in the visual storytelling. We're doing a horror film, and the ability to do shots with very shallow depth of field will be very useful to the storytelling. Digiprimes, as far as I understand, can't match the depth of filed and angle of view characteristics you get with the Pro35 adapter.

Not to mention that it's simply cheaper to rent the Pro35 and some Zeiss Superspeed Primes over the DigiPrimes, and our budget is tight. We can get a 600 day rate on the former, while the cheapest I've seen the latter is about $200 more than that.

Since almost all of the cave stuff will be shot on a set, and the real cave shots will be shot in an easily accessible commercial cave, I'm not too concerned about working with the Pro35 in difficult underground locations.

Brian:

Under what settings is the Varicam 640 ASA? I had recently seen somewhere that the Varicam was 250 ASA. Here is the link:

http://www.jkor.com/...varicamasa.html

I would be very happy if this wasn't the case and it was actually 640. We're shooting this for filmmout, and I am currently researching the best settings for that. But I figured they'd probably be pretty close to what this guy labels as 250 ASA.

Any thoughts on his chart?

Edited by Teddy Todd, 18 June 2005 - 11:01 AM.

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#13 Brian Wells

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Posted 18 June 2005 - 11:24 AM

I will humbly admit to repeating information presented at a workshop about the camera. The Japanese designers were present and informed our group in a Powerpoint of the recommended 640 ASA rating. It's also mentioned in my workshop binder. I cannot claim much firsthand operating experience other than as a participant in the (rather expensive) workshop.

The link you provided also mentions rating the camera at 640 as well, although it's kind of confusing and hard to follow. Excerpt from the last paragraph:

"Panasonic strongly recommends determining exposure using an incident light meter which is set to an Exposure Index of 640 (ASA). Their method closely follows the general techniques normally used for shooting film."

Hope this helps in some way. I would tend to prefer the lower light flexibility of primes rather than more depth of focus in this situation, for what it's worth.

Additionally, if film out is a certainty--or even if it isn't--please read carefully the defining difference between FILM REC and VIDEO REC. They are designed for entirely different applications.

The "Goodman's Guide" is the definitive resource on the subject.. $125 well spent.

Brian
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#14 Teddy Todd

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Posted 18 June 2005 - 11:37 AM

I will humbly admit to repeating information presented at a workshop about the camera.  The Japanese designers were present and informed our group in a Powerpoint of the recommended 640 ASA rating.  It's also mentioned in my workshop binder.  I cannot claim much firsthand operating experience other than as a participant in the (rather expensive) workshop.

The link you provided also mentions rating the camera at 640 as well, although it's kind of confusing and hard to follow.  Excerpt from the last paragraph:

"Panasonic strongly recommends determining exposure using an incident light meter which is set to an Exposure Index of 640 (ASA). Their method closely follows the general techniques normally used for shooting film."

Hope this helps in some way.  I would tend to prefer the lower light flexibility of primes rather than more depth of focus in this situation, for what it's worth.

Additionally, if film out is a certainty--or even if it isn't--please read carefully the defining difference between FILM REC and VIDEO REC.  They are designed for entirely different applications. 

The "Goodman's Guide" is the definitive resource on the subject.. $125 well spent.

Brian

<{POST_SNAPBACK}>


Brian,

Thanks for the recommendation. I haven't heard of the Goodman's Guide but I'll definitely be picking it up. According to that website, it seems the 640 ASA recommendation is for filmmouts and is essentially an underexposure - they say you can't look at the monitor for exposure, because it will be too dim. So they're asking you to underexpose by a stop and a half or so(250 ASA to 640 ASA), right?

Interesting.
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#15 Brian Wells

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Posted 18 June 2005 - 12:44 PM

So they're asking you to underexpose by a stop and a half or so(250 ASA to 640 ASA), right?
Interesting.

Sounds good to me. If HD exposes like reversal this conclusion would make sense. Unlike film, video does not have a consistent Exposure Index. The sensitivity can vary widely depending on the situation and light levels (my technical grasp ends there) and so meter recommendations are to be taken with a grain. The CreativeCow.com group has a VariCam board which would likely lead to even more positive results as many there have specialized experience in this area.

Hope this helps.
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#16 David Sweetman

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Posted 18 June 2005 - 01:19 PM

Just an idea, but maybe you'd want to throw some fire in there, like a torch or something. I love the look of fire on-screen, and this could offer more fill light to the faces, if the script allows it. I can just imagine the cool foley noises as they turn quickly -- FWOOSH!
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#17 Phil Rhodes

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Posted 18 June 2005 - 03:57 PM

Hi,

> "Panasonic strongly recommends determining exposure using an incident light meter
> which is set to an Exposure Index of 640 (ASA).

Well, that's a bit stupid.

Also:

> Unlike film, video does not have a consistent Exposure Index

It has a consistent sensitivity to light, assuming you don't go playing with camera settings, just the same way film is predictable so long as nobody screws up and you aren't using special processing. What makes you think this is not the case?

Phil
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#18 Brian Wells

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Posted 19 June 2005 - 01:37 AM

So they're asking you to underexpose by a stop and a half or so(250 ASA to 640 ASA), right?


...Um, wouldn't it be overexposing a stop and a half? 250 ASA film metered at 640 ASA would be overexposing, right? My head is spinning.
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#19 Alvin Pingol

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Posted 19 June 2005 - 02:44 AM

250 ASA film metered at 640 ASA would be overexposing, right?  My head is spinning.

<{POST_SNAPBACK}>


Underexposing! You're rating the film faster than it actually is, so you will thus be giving it less light than what it would need, if rated normally.
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#20 Brian Wells

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Posted 19 June 2005 - 03:39 AM

Underexposing! You're rating the film faster than it actually is, so you will thus be giving it less light than what it would need, if rated normally.

I can't see how I was confused so badly. Sorry.
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