Topics

Black grid butterflies

Art Adams
 

Hi all-

I have a crazy shoot coming up this week. Very ambitious, shooting every which way at once with multiple cameras, and we're in a courtyard where I have to knock ambient sunlight levels (f/32) to ambient dusk levels (f/2 or f/2.8). Shooting stop (for complex reasons I won't go into) is f/5.6 at ISO 400.

I'm looking at black fabrics for this, and my experience with them is limited as we don't have many options locally. It's also busy in town, so we're looking at overnighting rags in from LA. I need to knock out 8 stops, with the last four stops adjustable in roughly two stop increments (depending on director preference and cloud cover). I can't find any specs online as to what black or charcoal grid will do for me, so I'm wondering if someone can clue me in. We need 50'x50' minimum. 60'x40' could work but is not ideal.

This is all coming together fast (lots of final decisions this morning, of course) so any advice is appreciated.

Thanks.

--
Art Adams
Director of Photography
San Francisco Bay Area

Andy Cook
 

Hey Art, Black silk is 2 stops only. Modern has a rag called “night blue muslin” which is supposed to be opaque, but might be in the ballpark. 8 stops is a big ask as you know. I’m sure LA Rags or Modern can get you the exact stop info, and make something custom for you, quickly. 
Best,
Andy Cook 



On Jul 15, 2018, at 1:04 AM, Art Adams <art.cml.only@...> wrote:

Hi all-

I have a crazy shoot coming up this week. Very ambitious, shooting every which way at once with multiple cameras, and we're in a courtyard where I have to knock ambient sunlight levels (f/32) to ambient dusk levels (f/2 or f/2.8). Shooting stop (for complex reasons I won't go into) is f/5.6 at ISO 400.

I'm looking at black fabrics for this, and my experience with them is limited as we don't have many options locally. It's also busy in town, so we're looking at overnighting rags in from LA. I need to knock out 8 stops, with the last four stops adjustable in roughly two stop increments (depending on director preference and cloud cover). I can't find any specs online as to what black or charcoal grid will do for me, so I'm wondering if someone can clue me in. We need 50'x50' minimum. 60'x40' could work but is not ideal.

This is all coming together fast (lots of final decisions this morning, of course) so any advice is appreciated.

Thanks.

--
Art Adams
Director of Photography
San Francisco Bay Area

Jesse Harris
 

I know it’s a big ask, but perhaps you could double-up the rag and/or material.  Tough to rig for sure.

There’s also the “construction” plastics materials - we called it Vizquick here on the East Coast.  One sheet was 2.5-3 stops if I recall.  Bottom line however might mean combining materials.

Good luck!  Great shoot and let us know the results.

Jesse David Harris

Cinematographer | Editor


On Jul 15, 2018, at 10:58 AM, Andy Cook <aecook@...> wrote:

Hey Art, Black silk is 2 stops only. Modern has a rag called “night blue muslin” which is supposed to be opaque, but might be in the ballpark. 8 stops is a big ask as you know. I’m sure LA Rags or Modern can get you the exact stop info, and make something custom for you, quickly. 
Best,
Andy Cook 



On Jul 15, 2018, at 1:04 AM, Art Adams <art.cml.only@...> wrote:

Hi all-

I have a crazy shoot coming up this week. Very ambitious, shooting every which way at once with multiple cameras, and we're in a courtyard where I have to knock ambient sunlight levels (f/32) to ambient dusk levels (f/2 or f/2.8). Shooting stop (for complex reasons I won't go into) is f/5.6 at ISO 400.

I'm looking at black fabrics for this, and my experience with them is limited as we don't have many options locally. It's also busy in town, so we're looking at overnighting rags in from LA. I need to knock out 8 stops, with the last four stops adjustable in roughly two stop increments (depending on director preference and cloud cover). I can't find any specs online as to what black or charcoal grid will do for me, so I'm wondering if someone can clue me in. We need 50'x50' minimum. 60'x40' could work but is not ideal.

This is all coming together fast (lots of final decisions this morning, of course) so any advice is appreciated.

Thanks.

--
Art Adams
Director of Photography
San Francisco Bay Area


Josh Spring
 

I assume you have thought about “night for day” ?
If the situation allows, shooting @ night would give you total control, cabling across the courtyard and hanging a bunch of the new snazzy LED space lights. 


Josh Spring
Gaffer 
Various places 
301 461-0688


_._,_._,_

Art Adams
 

Thanks, Josh. I tried that, it didn't fly. To difficult to get the location for a night shoot, plus kids, etc. It would have been much, much easier, and cheaper as well.

--
Art Adams
Director of Photography
San Francisco Bay Area

Art Adams
 

Thanks, all. Production is going to poll the rag houses tomorrow morning and we'll figure out what to do after that. This shoot involves a lot of firsts, including a custom lighting rig that I'll have to fly above the courtyard once I get it dark enough. This really should be done on a stage, or at night (for day), or any of a number of other ways. Unfortunately, I'm stuck trying to make this work. If I can get the right materials I think it'll turn out really well.

Full grid and three layers of black silk would do it. I know black grid exists, and I'd much prefer that, but while I've seen it in butterfly form while operating "B" camera I've never used it personally.

--
Art Adams
Director of Photography
San Francisco Bay Area

Art Adams
 

Well, it was an interesting experiment. We went with the rags we were able to get on short notice from The Rag Place, all 40'x40':

Charcoal Vintage Grid (-4.1 stops)
Magic Cloth (-2.5)
Full Grid (-2.1)
Light Grid (-1.2)

(All stop loss measurements provided by The Rag Place.)

We started with Charcoal Vintage and mixed and matched rags, only to discover that the Charcoal Vintage just didn't spread the light the way I needed. We were shooting in an apartment complex and I needed the light to reach down three floors and wrap under the ground floor walkway, and it just didn't do that through the Charcoal. It's a bit like light grid where one can still see the sun through it, but it's softened a little. It also felt like it cut more light than four stops, although I didn't measure it with my meter as I was shooting stills to judge exposure.

We then tried layering all the white diffusions together, but that didn't do enough: there's something about putting white diffusion next to white diffusion that results in less stop loss than if I were softening a specular light source. My key grip's theory is that two white rags close together simply become the same light source.

Stacking the white rags should have given us wrap that the Charcoal Vintage didn't while cutting the same amount of light, but after the Magic Cloth went up as our base the additional rags only reduced overall illumination by a half stop or a stop. Instead of losing six stops we only lost about 3-3.5. Each additional rag cut light by about half of what it would do to a specular source.

We considered "striping" the diffusion with black visqueen, but the diffusion was close to the top of the structure and we were afraid we'd see regular dark patches along the roof line.

We threw a 20'x20' solid out into the center of the diffusion just to see what would happen but that only cut about a half a stop. I did the math a bit later and it worked out:

40x40 surface area: 1600 square feet
20x20 surface area: 400 square feet

If 1600 to 800 is one stop, then 1600-400=1200 is a half stop.

In the end we put down all three white rags, laid the Charcoal Vintage on top, and then rolled the Charcoal back about four feet on two sides. (The other two sides were tied down to truss with the other rags.) That gave us soft, slightly directional cross light while giving us very fine exposure control.

I keyed at 75fc using hard tungsten lights from the roof, under the diffusion, and kept the diffused daylight at 30-35fc. (White balance on the camera was around 4200K.) When clouds came in or the sun angle became steep we simply rolled up the sides a few more feet.

-- 
Art Adams
Director of Photography
San Francisco Bay Area

Jesse Harris
 

Interesting experiment and an even more interesting solution!

Thanks for the follow-up.

Jesse David Harris

Cinematographer | Editor

NYC



On Jul 20, 2018, at 11:29 AM, Art Adams <art.cml.only@...> wrote:

Well, it was an interesting experiment. We went with the rags we were able to get on short notice from The Rag Place, all 40'x40':

Charcoal Vintage Grid (-4.1 stops)
Magic Cloth (-2.5)
Full Grid (-2.1)
Light Grid (-1.2)

(All stop loss measurements provided by The Rag Place.)

We started with Charcoal Vintage and mixed and matched rags, only to discover that the Charcoal Vintage just didn't spread the light the way I needed. We were shooting in an apartment complex and I needed the light to reach down three floors and wrap under the ground floor walkway, and it just didn't do that through the Charcoal. It's a bit like light grid where one can still see the sun through it, but it's softened a little. It also felt like it cut more light than four stops, although I didn't measure it with my meter as I was shooting stills to judge exposure.

We then tried layering all the white diffusions together, but that didn't do enough: there's something about putting white diffusion next to white diffusion that results in less stop loss than if I were softening a specular light source. My key grip's theory is that two white rags close together simply become the same light source.

Stacking the white rags should have given us wrap that the Charcoal Vintage didn't while cutting the same amount of light, but after the Magic Cloth went up as our base the additional rags only reduced overall illumination by a half stop or a stop. Instead of losing six stops we only lost about 3-3.5. Each additional rag cut light by about half of what it would do to a specular source.

We considered "striping" the diffusion with black visqueen, but the diffusion was close to the top of the structure and we were afraid we'd see regular dark patches along the roof line.

We threw a 20'x20' solid out into the center of the diffusion just to see what would happen but that only cut about a half a stop. I did the math a bit later and it worked out:

40x40 surface area: 1600 square feet
20x20 surface area: 400 square feet

If 1600 to 800 is one stop, then 1600-400=1200 is a half stop.

In the end we put down all three white rags, laid the Charcoal Vintage on top, and then rolled the Charcoal back about four feet on two sides. (The other two sides were tied down to truss with the other rags.) That gave us soft, slightly directional cross light while giving us very fine exposure control.

I keyed at 75fc using hard tungsten lights from the roof, under the diffusion, and kept the diffused daylight at 30-35fc. (White balance on the camera was around 4200K.) When clouds came in or the sun angle became steep we simply rolled up the sides a few more feet.

-- 
Art Adams
Director of Photography
San Francisco Bay Area

AJ
 

Thanks for the followup Art! Fascinating. Can you share any of your exposure test photos?

Alan Jacobsen
DP - NYC


--
Alan Jacobsen 
DP - NYC

Art Adams
 

Unfortunately, I can't. Like most projects in the Bay Area, this one was done under NDA. I should be able to say more in October. It was pretty cool.


On Sat, Jul 21, 2018 at 3:48 AM AJ <arthurjacobsen@...> wrote:
Thanks for the followup Art! Fascinating. Can you share any of your exposure test photos?

Alan Jacobsen
DP - NYC


--
Alan Jacobsen 
DP - NYC



--
Art Adams
Director of Photography
San Francisco Bay Area

Leonard Levy
 

Very Interesting project art . I’m not surprised that multiple layers of diffusion had increasingly little effect as I’ve seen that for years even over a single light . In those cases closing the barn doors eventually  became  necessarywhich sounds like what you eventually did with solids .  I never have quite grasped why that is though . 

Leonard Levy , DP 
San Rafael , CA 



_._,_._,_

Justin Kuhn
 

I wonder what might have happened if you had been able to rig the white diffusion at different heights with some space between them instead of instead of stacking them on the same frame. Your solution sounds much easier than that, however.

Justin Kuhn
Indie Atlanta DP

Art Adams
 

That came up but it just wasn't feasible. I had the rig built about 4' off the roof as I had to put lights underneath it and my key grip was nervous about wind.


On Sun, Jul 22, 2018 at 11:16 PM Justin Kuhn <justinkuhn@...> wrote:
I wonder what might have happened if you had been able to rig the white diffusion at different heights with some space between them instead of instead of stacking them on the same frame. Your solution sounds much easier than that, however.

Justin Kuhn
Indie Atlanta DP



--
Art Adams
Director of Photography
San Francisco Bay Area