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Full CTB Gel


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#1 David McLeavy

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Posted 17 April 2008 - 02:32 PM

Okay, this feels lame to ask but I want to double check since I dont know much about gels. Is this all I would need to daylight balance a couple of Arri 1k tungsten kits:

http://www.bhphotovi...ilter_Full.html

And is that a good price for a roll? Advice welcomed!

Thanks,
Dave
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#2 robert duke

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Posted 17 April 2008 - 03:36 PM

$106 a roll is a pretty good price a roll for full CTB. CTB= color temperature correction Blue. According to rosco it will convert 3200' kelvin to 5500' kelvin.
it will reduce the output of your lights by 1.5 stops.

so this will balance 3200' lights with daylight, depending on the colortemp of daylight which changes through the day. but mostly yes.

now dont expect that you will be able to use those 1ks as a back light in full sun. In fact you may not even notice their output on a sunny day depending on their placement.


If you order it get a swatchbook too. flip through it and check out all the data that is there.
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#3 David McLeavy

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Posted 17 April 2008 - 05:15 PM

now dont expect that you will be able to use those 1ks as a back light in full sun. In fact you may not even notice their output on a sunny day depending on their placement.


I was planning more along the lines of adding some fill here and there for an indoor scene mixed with sunlight coming in through a window.
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#4 Walter Graff

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Posted 17 April 2008 - 05:56 PM

I was planning more along the lines of adding some fill here and there for an indoor scene mixed with sunlight coming in through a window.


Indoor light is 4400k even with rays of sunlight. You'd be better off using half blue than full blue. FYou'll also end up loosing so much light from full CTB
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#5 Michael Nash

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Posted 17 April 2008 - 06:07 PM

Indoor light is 4400k even with rays of sunlight.


That's a pretty broad statement! It depends on what indoor light sources are present. If all he's got is ambient daylight coming in, full blue on his tungsten should get it pretty close. Nothing wrong with cutting back on the density for a few extra footcandles though, if you don't mind the color of the window spill going a little cool.
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#6 Walter Graff

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Posted 17 April 2008 - 08:22 PM

That's a pretty broad statement! It depends on what indoor light sources are present. If all he's got is ambient daylight coming in, full blue on his tungsten should get it pretty close. Nothing wrong with cutting back on the density for a few extra footcandles though, if you don't mind the color of the window spill going a little cool.


Actually I don't find it broad at all. I have shot and measured hundreds of indoor scenarios with sun coming in and all and regardless of most situations with sun (no one is shooting direct sunlight on someones face indoors 99% of the time) the light tends to be closer to 4000k than 5600k. Hence why half ctb is always a better choice, especially when you don't have large lights. Easier to be warmer in color and than cooler. And easier to double up half CTB than only have a role of full.
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#7 Adrian Sierkowski

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Posted 17 April 2008 - 10:54 PM

I would tend to agree that 1/2 is a more versitile gel to have 'round. I tend to get all mt CTOs and CTBs as 1/2 and 1/4 strength, doubling up or adjusting as I need. It's nice to have full, of course, just I don't find it as versatile as 1/2 ya know?
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#8 Walter Graff

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Posted 18 April 2008 - 09:38 AM

In my 25 years of lighting I have learned one important thing when it comes to gels, always have something that works both ways. Having a roll of half when you are using it with smaller fixtures is always the way to go. It allows you to make more accurate and varied corrections. With full, you get full. With half you get half and full. Two for one!

As for ambient room temperature, I have found over the years that unless the sun is on the horizon and coming into a room, regardless of the ambient light outside, interior natural color temp from windows is between 4000k (overcast) and 4200k-4500k for direct and bounced sunlight. I just walked into a room in my apartment where the sun is bright outside. The room has big windows and the light is very bright. Took a reading.

sun1.jpg
sun2.jpg

Personally I’d always start with a half as a result and go from there. It will biring you to 4100k which gives that slightly warmer skin tome that I like. I find it better to have slightly more red in skin tones than cool blue. Makes the outside look nicer too when you make the indoors slightly warmer. But at these temperature differences the inside will not really look warmer to the eye if you supplement with 1/2ctb, just nicer.
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#9 Serge Teulon

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Posted 18 April 2008 - 09:54 AM

That's a busy front room you've got there Walter......what do you keep in the cage??

S
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#10 Walter Graff

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Posted 18 April 2008 - 12:25 PM

That's a busy front room you've got there Walter......what do you keep in the cage??

S


That the room that has become my kids playroom. Two bunnies in the cage.
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#11 Michael Nash

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Posted 18 April 2008 - 02:56 PM

Actually I don't find it broad at all. I have shot and measured hundreds of indoor scenarios with sun coming in and all and regardless of most situations with sun (no one is shooting direct sunlight on someones face indoors 99% of the time) the light tends to be closer to 4000k than 5600k.


And how many warm brick and concrete buildings are there around that apartment, reflecting warmer light? In my 20 years of shooting (and years of working with color before that) I've found that indoor light is highly dependent on the color(s) of whatever's outside bouncing light in, plus what's inside the room. I don't doubt what you see on your meter, but you can't say that applies to every room. An interior with hardwood floors will obviously have a warmer ambient color.

In another thread I had someone insisting that sunlight is much warmer than ambient daylight, and that you had to cool it off with CTB to use it as fill in exteriors. You're telling me the ambient daylight inside is always warmer. I'm saying 5600 works just fine. Are all three of us wrong?

Ambient light is the composite of the colors of all the sources and surfaces around. As those things change, the color of the light changes. For example, I've been picking paint colors for my back bedroom, which has large windows overlooking the mountains. Near the floor a gray trim color turns decidedly blue-gray (lit by blue sky), and near the ceiling that same color looks decidedly yellowish (lit by sunlight reflecting off trees and foliage). Against the windows (white walls), it looks neutral.

I'm sure I'm not the only one here who has been using exclusively 5600 light for day interiors for years with perfectly acceptable results. If 4400 blends better with the ambient light at the location, then use that.
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#12 Walter Graff

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Posted 18 April 2008 - 03:09 PM

And how many warm brick and concrete buildings are there around that apartment, reflecting warmer light?

None. All silver shinny buildings but none are close enough to those windows in the shot to do anything to any degree. Only direct sunlight is technically 5600k and even then only at noon on the right day. Right now at 4:05pm EDT the direct sun hitting my terrace is 4550k. My earlier post was done at 9:30am and had I taken a reading outside I probably would have gotten nearly what I got inside. And that is one of the reasons why any interior is always warmer than what we consider daylight. Cause most hours of the daylight, daylight is not daylight when it comes to what we think daylight should be.

My experience using a color meter on indoor shoots shows me that indoor light is warmer than daylight. I stand by my numbers as they are based on hundreds of readings over the years as I also showed in my impromptu read today. Are you wrong using 5600k fixtures in such a situation. No, as I said at these differences in color temps no one will notice. I just find that since most indoor light situations are closer to 4000k than 5600k it's easier to have lighter gels and smaller lights for fill and do the same thing as using 5600k with big lights. no one is wrong here, we all work differently and to taste. I like my outside to have cooler shades than inside. So slightly warmer inside makes for a cooler outside in some instances.
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#13 David Mullen ASC

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Posted 18 April 2008 - 11:05 PM

Daylight comes in so many colors due to weather, time of day, reflectance off of surfaces, etc. that you can pretty much choose whatever colors work for you creatively. It only matters when you are having to match exactly some bit of natural light with your artificial light, and even that, to some degree, can be eyeballed.

My general rule is that direct sunlight is warmer than ambient shade and skylight, so I generally fill with cooler light unless I am simulating -- or actually using -- the bounce back into the shadows from the reflection of warm sunlight. But I don't stick to that rule; on some movies, I've lit with hard cold blue-ish "sunlight" for creative reasons, even if that's not realistic. And I've had warm "overcast" soft light for other movies that isn't completely realistic either.

Sometimes warm faces are interesting against a colder background and sometimes the opposite is true...
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#14 Jonathan Bowerbank

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Posted 18 April 2008 - 11:34 PM

This past weekend I was mixing ambient afternoon daylight with an artificial 3/4 backlight. I had white balanced for the sunlight streaming in and placed full CTB on my chimera softbox, thinking it would match pretty closely. What I got was a very blue backlight...hmmm. It worked, because I just decided the blue light was blue skylight, but I was surprised as to how blue it really was. When I set my white balance to Preset 5600K the daylight was a little warm and backlight was perfectly white. So it just depends on what you're going for I guess.
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