Blue gel, what blue gel? at DVinfo.net

Mike Costantini · October 6th, 2006, 07:26 PM

I've been reading up on calibrating TVs or monitors and it looks as though I won't be able to get a pro monitor with a blue only switch ($$$). So can someone please tell me what the blue gel is, i.e. What do I ask for? and where do I get it?
Thanks so much,
Mike

Boyd Ostroff · October 6th, 2006, 07:59 PM

Roscolux R80 is pretty close to primary blue, but I think you would need to double or triple it up to get something close to the desired effect. You could order a single sheet from B&H:

http://www.bhphotovideo.com/bnh/cont...ughType=search

I'm sure there are also theatrical suppliers in Las Vegas which would have these in stock. Or if you know someone who works in live theatre they can probably get you some scraps or used cut gels for nothing :-)

Bill Hamell · October 7th, 2006, 05:34 AM

What you are looking for is a Kodak Wratten filter #47 or a comparable substitute.
The Kodak filter is expensive but not as expensive as a monitor with a blue gun. :-)

There may be other gels that work, however I have always used the Wratten filter with good results.

Bill

Mike Costantini · October 7th, 2006, 11:54 AM

Thank you!

Paul R Johnson · October 7th, 2006, 04:50 PM

primary blue gel won't quite do the job - because it is designed for removal of the red and green component of a light source at around 3200K - as in a tungsten halogen lamp - so to do the alignment properly you need the blue colour that your monitor uses, and unlike old grade 1 broadcast crt monitors with proper phosphor calibration specs, many current monitors don't tell you what they are balanced to, CT wise?

Mike Costantini · October 7th, 2006, 04:53 PM

English please? lol

Glenn Chan · October 7th, 2006, 09:47 PM

The blue gel trick (by itself) doesn't work very well, and here's a (hopefully simple) explanation why:

--The green elements in the monitor emits light of different wavelengths. i.e. it emits some red, orange, yellow, green, blue, violet light (i.e. picture all the colors of spectrum, if a beam of light were broken up by a prism). While it emits more green light than everything else, the green elements will emit a small amount of blue light.

This blue light will get through the blue gel.

2- You can use an alternate test pattern where you have smaller boxes of the opposite color, and the test pattern flashes those boxes on/off. You can calibrate the monitor by minimizing this flashing. A .veg for Vegas can be found on my training DVD ( http://vasst.com/product.aspx?id=221...a-fa0c83fa1dcd ).

However, not all consumer TVs can be calibrated like this, since they decode the chroma in a non-standard way.

3- You can get free gel sample books/swatches. Ree, Rosco, GAM make these.

Rental houses, theatrical supply, and broadcast supply places would have these for free. i.e. B&H has them for a penny.

4- A violet/purple gel will a sharp cutoff will work just as well. The swatchbooks will have graphs... look for a graph where the stop is really steep.

October 6th, 2006, 07:26 PM	#1
Mike Costantini Regular Crew Join Date: Feb 2004 Location: Las Vegas, NV Posts: 154	Blue gel, what blue gel? I've been reading up on calibrating TVs or monitors and it looks as though I won't be able to get a pro monitor with a blue only switch ($$$). So can someone please tell me what the blue gel is, i.e. What do I ask for? and where do I get it? Thanks so much, Mike

October 7th, 2006, 05:34 AM	#3
Bill Hamell Major Player Join Date: Aug 2004 Location: Mystic Ct. Posts: 477	What you are looking for is a Kodak Wratten filter #47 or a comparable substitute. The Kodak filter is expensive but not as expensive as a monitor with a blue gun. :-) There may be other gels that work, however I have always used the Wratten filter with good results. Bill __________________ Cinematographers Bring Shadow To Light

October 6th, 2006, 07:59 PM	#2
Boyd Ostroff Wrangler Join Date: Dec 2002 Location: Mays Landing, NJ Posts: 11,787	Roscolux R80 is pretty close to primary blue, but I think you would need to double or triple it up to get something close to the desired effect. You could order a single sheet from B&H: http://www.bhphotovideo.com/bnh/cont...ughType=search I'm sure there are also theatrical suppliers in Las Vegas which would have these in stock. Or if you know someone who works in live theatre they can probably get you some scraps or used cut gels for nothing :-)

October 7th, 2006, 11:54 AM	#4
Mike Costantini Regular Crew Join Date: Feb 2004 Location: Las Vegas, NV Posts: 154	Thank you!

October 7th, 2006, 04:50 PM	#5
Paul R Johnson Inner Circle Join Date: Nov 2005 Location: Lowestoft - UK Posts: 4,016	primary blue gel won't quite do the job - because it is designed for removal of the red and green component of a light source at around 3200K - as in a tungsten halogen lamp - so to do the alignment properly you need the blue colour that your monitor uses, and unlike old grade 1 broadcast crt monitors with proper phosphor calibration specs, many current monitors don't tell you what they are balanced to, CT wise?

October 7th, 2006, 04:53 PM	#6
Mike Costantini Regular Crew Join Date: Feb 2004 Location: Las Vegas, NV Posts: 154	English please? lol

October 7th, 2006, 09:47 PM	#7
Glenn Chan Inner Circle Join Date: Jun 2003 Location: Toronto, Canada Posts: 4,750	The blue gel trick (by itself) doesn't work very well, and here's a (hopefully simple) explanation why: --The green elements in the monitor emits light of different wavelengths. i.e. it emits some red, orange, yellow, green, blue, violet light (i.e. picture all the colors of spectrum, if a beam of light were broken up by a prism). While it emits more green light than everything else, the green elements will emit a small amount of blue light. This blue light will get through the blue gel. 2- You can use an alternate test pattern where you have smaller boxes of the opposite color, and the test pattern flashes those boxes on/off. You can calibrate the monitor by minimizing this flashing. A .veg for Vegas can be found on my training DVD ( http://vasst.com/product.aspx?id=221...a-fa0c83fa1dcd ). However, not all consumer TVs can be calibrated like this, since they decode the chroma in a non-standard way. 3- You can get free gel sample books/swatches. Ree, Rosco, GAM make these. Rental houses, theatrical supply, and broadcast supply places would have these for free. i.e. B&H has them for a penny. 4- A violet/purple gel will a sharp cutoff will work just as well. The swatchbooks will have graphs... look for a graph where the stop is really steep.