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Old July 25th, 2010, 01:25 AM   #1
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CTB vs Dichroic filter to convert to Daylight?

I've always used blue gels to convert my Arri 650 and 1k open face tungsten lights to daylight; of course I lose a lot of wattage. Does anyone know if the Dichroic filter that Arri makes passes more light through than the gel? It's around $150, so I want to be sure it's worth it before I buy!

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Old July 25th, 2010, 02:43 AM   #2
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can this really not be fixed in post? Seems so expensive, when a click of a mouse would fix it. ?
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Old July 25th, 2010, 05:48 PM   #3
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no it can't. you can get close, sometimes, depending on the filter you use, but good filter sets costs quite a bit and you lose more time trying to fix things than shooting it right. light and the color of it is one thing i would never leave to post. ideally color adds mood and depth to your story, and so much of that potential is lost if you need to focus on just fixing things.

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Old July 25th, 2010, 07:14 PM   #4
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Yes, I agree; trying to fix it in post is the worst way to solve problems! That's why I'm trying to solve the problem this way; so I can keep my editor editing, rather than fixing.
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Old July 25th, 2010, 09:50 PM   #5
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I always understood the dichroic filters were a neater looking solution but otherwise did the same job.

The wattage of your lamps is, of course, not affected by any filters - any illumination lost to the filters would be a reduction of lux (foot-candles in the USA). This is, of course, only a technicality - we'd both agree that the filters reduce the "light".
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Old July 25th, 2010, 10:01 PM   #6
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So just to be clear, you think then that the loss of lux is about equal, whether or not I use a gel or the dichroic lens?
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Old July 25th, 2010, 10:16 PM   #7
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Bruce, my guess (and it is just that) is yes. But look at it the other way, if there were inherent disadvantages in using the dichroic filters (like a greater reduction in lux) how could Arri justify charging the arm and a leg they do? You can buy yards of half blue and dozens of pegs for $150.
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Old April 5th, 2015, 10:09 PM   #8
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Re: CTB vs Dichroic filter to convert to Daylight?

I would think you could have more flexibility by using a dichroic. Say you need to change tungsten to daylight balance (here's where you would use the dichroic), then still use a gel in your gel frame for color effects (shining red light on your background, etc.) That's the main benefit I see.
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Old April 6th, 2015, 03:20 AM   #9
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Re: CTB vs Dichroic filter to convert to Daylight?

That's a 5 year old thread you are replying to and none of the users in this thread have been active on this forum anymore. :)
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Old April 9th, 2015, 08:31 PM   #10
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Re: CTB vs Dichroic filter to convert to Daylight?

Quote:
Originally Posted by Dale Cornibe View Post
I would think you could have more flexibility by using a dichroic. Say you need to change tungsten to daylight balance (here's where you would use the dichroic), then still use a gel in your gel frame for color effects (shining red light on your background, etc.) That's the main benefit I see.
Well, now that Dale's raised this thread from the dead, I am kind of interested. It's been ages since I've had to use gels or hot lights, so here's two dumb questions for any knowledgeable person out there:

-- In Dale's example above, couldn't you just use the red gel without the dichroic? Why would you need to convert to daylight first?
-- If you really wanted to convert to daylight first, couldn't you stack a CTB and a red gel in front of the light, without the need for the dichroic?

By the way, I've never used a dichroic, but I suspect the main advantage is less light loss, and main disadvantage is that it gets "warmer" over time:

Dichroic filters instead of CTB
Dichroic Filter vs Full CTB?
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