IR Contamination..any further forward??

Leonard Levy · May 13th, 2009, 09:11 PM

My memory is getting fuzzy about what Art and I tested as he brought a bunch of filters. I thought he brought both the Rosco and the IR pola and that neither knocked my socks off on the EX. But i should check back with him.

I know that the 486 was extremely effective and it remained equally effective no matter how much standard ND you added.

Likewise I was unimpressed with the Tiffen IR ND's. They seemed pretty ineffective until we got up to massive amounts of ND. i.e the N21 looked reasonably effective but the N6 did nothing.

Leonard Levy · May 14th, 2009, 07:43 PM

Be patient and cross your fingers.

Brian Cassar · May 15th, 2009, 12:52 AM

Leonard,

Does Tiffen produce any IR cut filter without any ND built in? I'm not interested what happens when one adds further ND's. My problem is being encountered indoors under tungsten lights (when obviously I would be shooting in filter 1 and most of the time, almost a wide open apeture so as to film with available light). At present I'm using the 486, with excellent black rendition but I'm closing my eyes for the peripheral green tint.....!

Derek Reich · May 15th, 2009, 06:57 AM

Quote:

Originally Posted by Brian Cassar

Leonard,

Does Tiffen produce any IR cut filter without any ND built in? I'm not interested what happens when one adds further ND's. My problem is being encountered indoors under tungsten lights (when obviously I would be shooting in filter 1 and most of the time, almost a wide open apeture so as to film with available light). At present I'm using the 486, with excellent black rendition but I'm closing my eyes for the peripheral green tint.....!

Adding ND to the Tiffen ColorCore (IRND) filters that is NOT another IRND filter will allow more IR contamination to show in your image. As mentioned repeatedly in these forums, the Tiffen filters base the amount of dye needed to correct the contamination by the level of ND in the particular filter. You MUST use their IRNDs for ANY ND needed when using the IRNDs to correct for contamination. No other NDs can be used, not even the ones built into the camera. Stick with your 486, at the moment it's the best option we have for eliminating the contamination.

That said, I'm very curious about the possibility of using a polarizer in conjunction with the 486/680 to offset the green vignetting. When I get a chance, (which is not soon) I'll give this a try. If Schneider is playing with a combination of the two, it makes some sense (I hope) that this might work with a separate pola too.

Leonard Levy · May 15th, 2009, 10:35 AM

Brian,
Tiffen is working on a dye filter for IR without ND. Results are promising but it is still in development. Cross your fingers as this would be what we want.

Derek,
In theory you are correct, however current Tiffen IRND's are just not very effective on the EX-1. Hopefully a better dye solution for tungstun will result in a better ND solution as well.

Bob Grant · May 18th, 2009, 10:08 PM

Just by chance I had a talks with these people today Optical Manufacturing. Person I spoke with immediately understood our problem and does have a solution as they have developed a process for making dichroic filters without the vignetting issue by adjusting layer thickness over radius. Unfortunately the process is very slow, the design is difficult and the cost (probably an order of magnitude greater than a 486) would not make it a viable solution. My offer of an immediate order for 1,000 filters created no interest. My understanding is that their process has never been used commercially due to the cost. All that seems to remain of their work is a very interesting prototype in the showroom. Perhaps if some wealthy benefactor would like to kick in a couple of million in seed capital we could get them interested again.

Leonard Levy · May 18th, 2009, 11:02 PM

Bob, I've wondered whether some kind of a rounded filter like the front element of a lens but without optical characteristics ( if that's possible) might work as well.

Bob Grant · May 19th, 2009, 12:16 AM

Quote:

Originally Posted by Leonard Levy

Bob, I've wondered whether some kind of a rounded filter like the front element of a lens but without optical characteristics ( if that's possible) might work as well.

I floated exactly that idea to the guy from Francis Lord!
The problem is the vacuum depositing process would not deposit an even layer of metal, it would get thinner towards the edge. Now that at first might seem like a good thing however balancing that and the change in angle of incidence might be a task and a half.

He did say that adding a polarizer in front of the dichroic is another solution but as we know you loose light.

I visit these people fairly regularly as we buy our Storm cases from them. I'll try to persue any and all ideas however I came away from the discussion with the feeling that any optical problem can be solved....if you're prepared to pay for it. It's not just the cost of manufacture. They need the best brains around to work on these problems and the few there are work in public funded research which does not sit too well with commercial ventures. These guys are sure serious, the specs on the mirrors they helped grind for the LIGO telescopes are mind boggling, around 1 atom thinkness tolerance.

Dean Harrington · May 19th, 2009, 02:02 AM

Quote:

Originally Posted by Bob Grant

I floated exactly that idea to the guy from Francis Lord!
The problem is the vacuum depositing process would not deposit an even layer of metal, it would get thinner towards the edge. Now that at first might seem like a good thing however balancing that and the change in angle of incidence might be a task and a half.

He did say that adding a polarizer in front of the dichroic is another solution but as we know you loose light.

I visit these people fairly regularly as we buy our Storm cases from them. I'll try to persue any and all ideas however I came away from the discussion with the feeling that any optical problem can be solved....if you're prepared to pay for it. It's not just the cost of manufacture. They need the best brains around to work on these problems and the few there are work in public funded research which does not sit too well with commercial ventures. These guys are sure serious, the specs on the mirrors they helped grind for the LIGO telescopes are mind boggling, around 1 atom thinkness tolerance.

Glen Davis over at Francis Lord optics did suggest, in a query I sent, that we talk to Dr David MacKenzie at the University of Sydney on this matter. I have no idea what that means but you are in Auz and may be better suited to contact the good professor to get a heads up.

Bob Grant · May 19th, 2009, 04:37 AM

Quote:

Originally Posted by Dean Harrington

Glen Davis over at Francis Lord optics did suggest, in a query I sent, that we talk to Dr David MacKenzie at the University of Sydney on this matter. I have no idea what that means but you are in Auz and may be better suited to contact the good professor to get a heads up.

Thanks Dean,
I'll try to follow this up for all of us.

Serena Steuart · May 19th, 2009, 07:57 PM

Progress: ProVideo Coalition.com: Stunning Good Looks by Art Adams | Cinematography

Dean Harrington · May 19th, 2009, 08:33 PM

Quote:

Originally Posted by Serena Steuart

Progress: ProVideo Coalition.com: Stunning Good Looks by Art Adams | Cinematography

The filter seems to cover the need. Of course, I'll be picking one up as soon as it's available. kuddos to Art for his work!!!

Leonard Levy · May 19th, 2009, 08:55 PM

OK Art broke the news, in a very informative article. That's what i was referring to when I said be patient and cross your fingers. Art and I have been talking to Tiffen about trying to make, a dye based IR filter for Tungstun and the prototype looks very promising. This would be a great step forward for us.

Kudos also to Robert Orlando and his team at Tiffen.

I hope to get one to test soon as well.

Hopefully, getting this right will help them nail down the correct amount of green for effective IR ND filters on the EX-1 as well. I hope you don't end up needing different IR and IRND's for every camera.

Wouldn't it be nice if this thread could be retired at last.

Bob Grant · May 20th, 2009, 01:54 AM

The engineer in me says that we're going about this the wrong way. The correct approach should be to plot the spectral response of the EX cameras and at ND0, 1 & 2. From that we should know what the spectral transmission of the filter needs to be and any other issues we might have.
I could possibly, maybe get access to the needed light source but I'm totally at a loss as to how to use that to measure the response of the camera, would something as basic as a waveform monitor do?
How do we calibrate out white balance?

David Herman · May 20th, 2009, 04:17 AM

Gents, much learned from this discussion and tons of appreciation for the sharing. For myself, who is expecting his ex3 next week, and a non understander of the technical reasons why, I can only ask, where do I avail myself of the 486 filter in the UK?

May 18th, 2009, 10:08 PM	#21
Bob Grant Trustee Join Date: Nov 2005 Location: Sydney Australia Posts: 1,570	Found someone who could make us a filter. Just by chance I had a talks with these people today Optical Manufacturing. Person I spoke with immediately understood our problem and does have a solution as they have developed a process for making dichroic filters without the vignetting issue by adjusting layer thickness over radius. Unfortunately the process is very slow, the design is difficult and the cost (probably an order of magnitude greater than a 486) would not make it a viable solution. My offer of an immediate order for 1,000 filters created no interest. My understanding is that their process has never been used commercially due to the cost. All that seems to remain of their work is a very interesting prototype in the showroom. Perhaps if some wealthy benefactor would like to kick in a couple of million in seed capital we could get them interested again.

May 13th, 2009, 09:11 PM	#16
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	My memory is getting fuzzy about what Art and I tested as he brought a bunch of filters. I thought he brought both the Rosco and the IR pola and that neither knocked my socks off on the EX. But i should check back with him. I know that the 486 was extremely effective and it remained equally effective no matter how much standard ND you added. Likewise I was unimpressed with the Tiffen IR ND's. They seemed pretty ineffective until we got up to massive amounts of ND. i.e the N21 looked reasonably effective but the N6 did nothing.

May 14th, 2009, 07:43 PM	#17
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	Be patient and cross your fingers.

May 15th, 2009, 12:52 AM	#18
Brian Cassar Major Player Join Date: Jan 2007 Location: Malta Posts: 306	Leonard, Does Tiffen produce any IR cut filter without any ND built in? I'm not interested what happens when one adds further ND's. My problem is being encountered indoors under tungsten lights (when obviously I would be shooting in filter 1 and most of the time, almost a wide open apeture so as to film with available light). At present I'm using the 486, with excellent black rendition but I'm closing my eyes for the peripheral green tint.....!

May 15th, 2009, 10:35 AM	#20
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	Brian, Tiffen is working on a dye filter for IR without ND. Results are promising but it is still in development. Cross your fingers as this would be what we want. Derek, In theory you are correct, however current Tiffen IRND's are just not very effective on the EX-1. Hopefully a better dye solution for tungstun will result in a better ND solution as well.

May 18th, 2009, 11:02 PM	#22
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	Bob, I've wondered whether some kind of a rounded filter like the front element of a lens but without optical characteristics ( if that's possible) might work as well.

May 19th, 2009, 07:57 PM	#26
Serena Steuart Major Player Join Date: Jun 2006 Location: Studio Alnitak, Melbourne, Victoria, Australia Posts: 640 Images: 3	Progress: ProVideo Coalition.com: Stunning Good Looks by Art Adams \| Cinematography

May 19th, 2009, 08:55 PM	#28
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	OK Art broke the news, in a very informative article. That's what i was referring to when I said be patient and cross your fingers. Art and I have been talking to Tiffen about trying to make, a dye based IR filter for Tungstun and the prototype looks very promising. This would be a great step forward for us. Kudos also to Robert Orlando and his team at Tiffen. I hope to get one to test soon as well. Hopefully, getting this right will help them nail down the correct amount of green for effective IR ND filters on the EX-1 as well. I hope you don't end up needing different IR and IRND's for every camera. Wouldn't it be nice if this thread could be retired at last.

May 20th, 2009, 01:54 AM	#29
Bob Grant Trustee Join Date: Nov 2005 Location: Sydney Australia Posts: 1,570	The engineer in me says that we're going about this the wrong way. The correct approach should be to plot the spectral response of the EX cameras and at ND0, 1 & 2. From that we should know what the spectral transmission of the filter needs to be and any other issues we might have. I could possibly, maybe get access to the needed light source but I'm totally at a loss as to how to use that to measure the response of the camera, would something as basic as a waveform monitor do? How do we calibrate out white balance?

May 20th, 2009, 04:17 AM	#30
David Herman Regular Crew Join Date: Sep 2003 Location: gloucestershire uk Posts: 93	Gents, much learned from this discussion and tons of appreciation for the sharing. For myself, who is expecting his ex3 next week, and a non understander of the technical reasons why, I can only ask, where do I avail myself of the 486 filter in the UK?