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HT gel


alex_hughes

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Hello,

 

Ordered some HT Congo Blue from LEE for a show, all of the blue costumes turned red. Is it because of the HT format or because it's congo blue?

 

Has anyone encountered this before?

 

Cheers

 

Alex

 

A concurrent post has been automatically merged from this point on.

 

Haha, I've also just learned that apparently Congo Blue is completely transparent to Infra-Red light but I don't imagine that this can be the cause of the problem....

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Hello,

 

Ordered some HT Congo Blue from LEE for a show, all of the blue costumes turned red. Is it because of the HT format or because it's congo blue?

Nothing at all to do with the temperature rating of the gel...

 

I suggest you do some reading on colour filters and what they do to different colour fabrics/scenery and why.

 

Just why did you decide to order Congo Blue anyway?

Was it a conscious decision based on experience or just 'oooh, that looks nice in the swatch...!'?

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If you look at the transmission graph in the swatch - you'll see something that looks like THIS. All that red is going to react differently on different fabrics depending on their own specific absorption and reflective characteristics. That's why it's imperative to do colour tests as part of your design scheme until you are positive that you'll get the results you want. It has nothing to do with the HT rating.
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Hello,

 

Ordered some HT Congo Blue from LEE for a show, all of the blue costumes turned red. Is it because of the HT format or because it's congo blue?

Nothing at all to do with the temperature rating of the gel...

 

I suggest you do some reading on colour filters and what they do to different colour fabrics/scenery and why.

 

Just why did you decide to order Congo Blue anyway?

Was it a conscious decision based on experience or just 'oooh, that looks nice in the swatch...!'?

 

Strictly speaking it's very little to do with me, It's for a student in a school. Their teacher insisted he has it in his design. I've never actually used that colour before, generally because it has such a low light transmission and because I think it's closer to purple than blue really....

 

"Was it a conscious decision based on experience or just 'oooh, that looks nice in the swatch...!'?"

 

I expect it's more to do with the latter. She said 'It's never happened before' (hence me asking if it's to do with the HT format) although I reckon that she's never actually put any blue fabric under that colour light before. Edit: on that note though, neither have I.

 

My suspicion is because she's using fabrics with reflective qulaities and they're picking up the red in the filter.

 

A concurrent post has been automatically merged from this point on.

 

If you look at the transmission graph in the swatch - you'll see something that looks like THIS. All that red is going to react differently on different fabrics depending on their own specific absorption and reflective characteristics. That's why it's imperative to do colour tests as part of your design scheme until you are positive that you'll get the results you want. It has nothing to do with the HT rating.

 

Thanks for that link, seeing it visually makes all the difference, and makes a lot more sense to me (my background is as a sound tech, but with just enough experience to get by with lighting, but not as a designer by any stretch of the imagination)

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As others post, congo blue transmits a small amount of deep red light, and dependent on the exact dye formulation used for the blue fabrics, could make them appear red.

 

Also though, note that congo blue transmits a certain amount of near UV and deep violet, these wavelengths cause flourescence in certain materials,not just paints and dyes sold for the purpose, but also fabrics that have been laundered with modern detergents.

 

This is more noticable with discharge lamps, but does occur with incandescent sources.

 

If it is desired to reduce the red content of the light, then 713 winter blue which transmits no red might have been a better choice, or 071 tokyo blue which transmits much less red than congo blue.

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Thanks to Gerry for link if it dosent` break, the Samoiloff Effect:

 

http://query.nytimes.com/gst/abstract.html...FB667838A639EDE

 

http://books.google.co.uk/books?id=MPGxn3n...result#PPA36,M1

 

Though tempted to say ask on Stagecraft mailing list, sure a certain Frank Wood would have some comments on use of Congo Blue ;-)

 

 

Thanks everyone who's posted, still very n00bish on LX, it's actually pretty daunting!

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I have a black pullover I frequently wear for non-performance run-throughs, its old and comfy, and I like it. And under the blues it becomes a cute browny-purple. It does surprise people when they see this - "your pully changes colour - how neat is that - where can I get one of them?"
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It's not just blues that turn dark red, a lot of blacks will do the same thing under particular blue gels. Almost all my stage blacks will turn red under some blue gels - I've always found that it tends to be the blues which don't go green at low level which react with black dyes.
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