Filter for IR contamination

Brian Cassar · February 27th, 2009, 06:06 AM

This twist in this issue is very interesting but confusing as well. I cannot understand why in the test only ND IR cut filters were used. The problem is more accentuated under halogen lights than when filming in broad daylight. So any loss of light due to ND filter is unacceptable especially when shooting under available light (and not controlled lighting).

Can someone explain whether these Tiffen ND IR filters can be produced without the ND component in them - just IR cut only? Or is it not possible to have an IR cut filter which works well without some ND inside it? The 486 does not have any ND but then again it does not work well.

Piotr I have to disagree also with you on point No.4. I used to say the same thing like you said but after receiving my new Zylight 90 just yesterday I will not use any halogen on-board light again. The Zylight 90 is the LED lamp to use for ENG. It's true that it is very expensive (it took me a year to decide to buy it) but the ability to switch the colour temp at the touch of a button without using any light reducing coloured gels in front of the led's is fantastic. I haven't used it in an assignment but from the tests I did yesterday it's absolutely amazing! I bought it specifically to eliminate the halogen light on board of the EX3 which was causing too much contamination.

Piotr Wozniacki · February 27th, 2009, 06:23 AM

Quote:

Originally Posted by Bob Grant

To put it simply , Adam has confirmed the nature of the problem, we still do not have a solution. Shooting stage shows with a ND1 filter on the camera even if it cured the problem is not an option, period.

I couldn't agree more with this last statement, Bob (with a little correction - we're not talking Adam Wilt's article here, but that of Art Adams :)).

However - after having tried the screw-on 486 and 489 - I'm now having a 4x5.65" filter from a manufacturer whose name I'd prefer not to reveal at the moment. I have just completed a quick and dirty series of tests, and here are my results...

1. YES, even in daylight at 5600K, the blacks CAN be a bit contaminated - just compare the first pair of my grabs (upper left - no filter, upper right - with filter X)

2. In tungsten light at preset 3200K, EVERYTHING is too red - but still the middle right picture (with filter X 3200K) shows some improvement over no filter (middle left) (BTW, sorry I forgot to re-focus on the main subject - the bag - after I had to open up the iris due to lower light)

3. As I said before, dialing WB down to 2700K (to balance at the white card) allows to minimize the red contamination (bottom left - no filter), and the filter I tested makes the black ALMOST completely black (bottom right).

Conclusions:

1) 3200K is commonly used as the right preset for tungsten lighting; looking at the grabs, it's obviously too hot - always do white balancing before actual shooting! It seems to have much stronger influence on the alleged "IR problem", than using a Hot Mirror filter...

2) The B+W 486 filter can get rid of ALL contamination (see my comparison grabs in another thread); should it not produce the ugly, greenish vignette at wide angles, it would be the best solution for the EX cameras... Just what kind of filter is it ?!!

Comments welcome!

Piotr Wozniacki · February 27th, 2009, 06:28 AM

Quote:

Originally Posted by Brian Cassar

It's true that it is very expensive (it took me a year to decide to buy it) but the ability to switch the colour temp at the touch of a button without using any light reducing coloured gels in front of the led's is fantastic...

Sure - if you can change the light temperature, it's great (and expensive:))...

I used to have the Sony on-camera LED light (no 3200 filter - just 5600K; 4000K with dimmer on), and in situations I mentioned above (where the surroundings were more towards 2700 - 3000K), faces did look ugly.

Of course, I might have used some amber gelling, but then the lumen/watt ratio would drop dramatically down to a regular, halogen lamp that I'm using now. Much smaller and versatile!

Brian Cassar · February 27th, 2009, 07:34 AM

Quote:

Originally Posted by Piotr Wozniacki

3. As I said before, dialing WB down to 2700K (to balance at the white card) allows to minimize the red contamination (bottom left - no filter), and the filter I tested makes the black ALMOST completely black (bottom right).

Piotr, whenever I've encountered IR contamination (or whatever it is...), under halogen lights, I've always manually white balanced on a white paper and got a reading of about 2600-2700K. I never use preset and yet I've witnessed some horrible black-turned-brown fabrics. Seeing your test, I'm now wondering whether I should use the warm cards at all in such situation. I was intending to start white balancing always with the 1/4 Blue to warm a bit the picture but will need to do some tests as the warming effect might enhance the "contamination".

I'm also wondering why some people have stated that they are not seeing the green tint with the 486. Could it be some manufacturing inaccuracies that are producing the ideal filter unintentionally and unknowingly?

Brian Cassar · February 27th, 2009, 03:15 PM

I think I found a temporary solution to this IR contamination problem. As I had indicated before I tend to film a lot under available light (without any fill in light) which on most time is predominantly halogen. This was obviously giving me loads of problems with black material.

I have just done a very quick test - I filmed a black t-shirt under available halogen light. This as expected turned to a brownish tint. I then switched on the newly bought Zylight 90 and since this is LED light the black t-shirt was restored immediately back to black! Even when I had dimmed the light to almost minimum, as long as a very small quantity of LED type of light fell on the black fabric, the problem disappeared (without the use of any filter). Please note that the Zylight was switched on the 3200K setting so as not to disrupt the white balance that had been set to the prevailing halogen light.

This means that unfortunately I have to change my style of filming and start using some dimmed fill-in LED light whenever there is halogen light as the main source of lighting. As I said this was a very quick test. I have yet to test it out in a proper shoot - but I'm expecting the same type of results that I had obtained today.

Bob Grant · February 27th, 2009, 03:19 PM

Quote:

Originally Posted by Brian Cassar

I'm also wondering why some people have stated that they are not seeing the green tint with the 486. Could it be some manufacturing inaccuracies that are producing the ideal filter unintentionally and unknowingly?

It took me a long time before I noticed it.
That's always the problem in this game, deciding what matters and what doesn't.
Looking at a couple of screenshots that Piotr supplied I can see it quite clearly however I believe the camera was not WB after fitting the filter so the whole frame does have a bit of green caste to start with, it gets worse towards the edges for sure. One reason it's not been so obvious to me is the filter is always on my camera, as are all the other ones in our fleet so the cameras are always being WB'ed with the filter on.
So again the question is not is it there, the question is does it matter. I'd suggest it doesn't as the eye is not naturally drawn to it. Maybe it'd be different if the subject was up against a white wall but such shots are rare. On the other hand people wearing black sitting large in the middle of the frame are very common. The visual effect of the 'IR' problem does seem very distracting to the average normal viewer as there's nothing naturally like it. On the other hand a bit of fall off or caste towards the edge of a wide shot mimics what is sometimes seen in the natural world.

Brian Cassar · February 27th, 2009, 03:43 PM

Quote:

Originally Posted by Bob Grant

The visual effect of the 'IR' problem does seem very distracting to the average normal viewer as there's nothing naturally like it. On the other hand a bit of fall off or caste towards the edge of a wide shot mimics what is sometimes seen in the natural world.

Well said - I fully agree with this reasoning. However on the other hand I remember the fuss that was kicked up on the very small vignetting that the early EX1's had and yet now we are creating a much larger and coloured vignetting.

Tip McPartland · February 27th, 2009, 04:50 PM

I'm sure everyone's white balanced through 1/8 or 1/4 CTB to warm up their subjects. I used to do this and sometimes I would also add 1/8 green, can't remember the exact gel. I started doing this when I would have to shoot with existing fluorescent lights, but then I came to think a little less green was good for skin tones much of the time.

What occors to me is that perhaps a gel or combination of gels the same color as the fringing, or as close as possible, could be used during the white balance.

The result would be a neutral color balance where the vignetting would have been, and a bit less green/cyan in the center where the subject is. This might look nice, or at least nicer than a bias in portions of the picture toward the green side.

Tip McPartland

Serena Steuart · February 27th, 2009, 06:47 PM

Generally outdoors I do not use any additional IR filtering (while Bob uses it as default), but it isn't true to say that the IR problem isn't present under 5600K lighting. Attached are two recorded in sunlight (white balanced internal camera ND filters) and the black artificial fibre is recorded black only with the BW486 filter.

Also, when suggesting that the default 3200K setting is too hot (which I haven't checked, I always WB) how was the colour temperature of the lights measured? Maybe they were not 3200K.

Clark Peters · February 27th, 2009, 07:03 PM

Quote:

Originally Posted by Brian

Can someone explain whether these Tiffen ND IR filters can be produced without the ND component in them - just IR cut only? Or is it not possible to have an IR cut filter which works well without some ND inside it?

It's my impression from Art's article that you can almost consider the successful filter to be a correction filter. All correction filters (all filters, really) involve a loss of light. The filter factor of an 80A is 2 stops. A one stop loss for a filter that corrects the IR "contamination" seems pretty reasonable and should be expected.

I'd be very curious to see the results from someone using the 0.3 filter.

By the way, I haven't been able to find anyplace selling the non-Hot Mirror version of this filter. Anyone have a suggestion?

Pete

Derek Reich · February 27th, 2009, 07:44 PM

Quote:

Originally Posted by Clark Peters

It's my impression from Art's article that you can almost consider the successful filter to be a correction filter. All correction filters (all filters, really) involve a loss of light. The filter factor of an 80A is 2 stops. A one stop loss for a filter that corrects the IR "contamination" seems pretty reasonable and should be expected.

I'd be very curious to see the results from someone using the 0.3 filter.

By the way, I haven't been able to find anyplace selling the non-Hot Mirror version of this filter. Anyone have a suggestion?

Pete

Hello, Pete-
I'm not sure what size filter you want, but I know Filmtools in CA (Filmtools: Hollywood's source for grip, electrical, lighting, sound, video and film supplies) can special order a non-hot mirror version in a 4x4. 4x5.65 are readily available, I've found them at a number of retailers, but for the 4x4, Tiffen has to apparently cut the filter upon order, which will take approximately two months. I guess they don't have enough demand for the filter in a 4x4 to have any ready to go. I'm not sure if it's available at all in a 77mm.

Piotr Wozniacki · February 28th, 2009, 03:03 AM

Quote:

Originally Posted by Serena Steuart

Also, when suggesting that the default 3200K setting is too hot (which I haven't checked, I always WB) how was the colour temperature of the lights measured? Maybe they were not 3200K.

This is a very important point, Serena - I didn't measure, I just used my EX1's 3200K preset. Could it be that the WB system in my specific unit is not calibrated well? Because it's obviously too hot for tungsten; when I balanced to the white card (not changing anything else), the WB settled at 2700K !

Can anyone confirm or deny the same happens with their unit(s), or is my unit defective?

It's extremely important to me to know whether I can trust the presets, as I often shoot live stage performances with other EX1's; of course we could balance all 3 to the same white card, but using a preset is much safer (I mean, with the WB switch set to memory A or B, it's all so easy to inadvertently knock the AWB button and lose the setting - while when it's in a preset position, it's 100% safe).

Serena Steuart · February 28th, 2009, 05:50 AM

The difficulty with tungsten is that the colour temperature is quite sensitive to lamp voltage and age, so we can't be really sure about its colour temperature without measuring (hence the colour temperature meter). You can measure the voltage when the lamp is on and if that matches the designated lamp voltage then you won't be far out. Our supply here, for example, is supposed to be 230v AC, but varies between 220 and 245 (depending on district load) and I have seen it below 210. Stage lighting is generally on dimmers, so the CT can vary quite a bit across the stage and in time.
Today I did run a test using a RedHead QI and the camera WB, 3200 preset and colour temp meter all agreed within +/-100K . The EX1 WB gave me 3100K and I couldn't see the difference switching to the preset.
The thing is to make sure all cameras match in their settings, because matching in post is a pain. You can, as you know, pre-set any CT you find appropriate, so the 3200 factory pre-set isn't operationally critical.

Leonard Levy · February 28th, 2009, 01:21 PM

Piotr,
I'm having trouble identifying exactly what problem your having because I don't know what lights you were using or for that matter how much background you may be bringing to your understanding. Please excuse me if it sounds like I'm talking down here.

It looks like you you shot the test of the chair under ordinary household tungstun bulbs which are not 3200 but closer to 2600- 2900K so of course the picture would appear red.
Alternatively Serena is right that if your voltage is lower than what even professional photo lamps are rated for (usually 3200) the same thing would happen.

This has nothing at all to do with IR contamination, just ordinary white balance and color temperature. IR is something that only affects some fabrics in an otherwise well color balanced shot.

It is interesting though that people with the EX on these boards have been complaining mostly about IR under Tungstun light rather than in daylight while using ND while complaints about the RED seem to center more about ND problems. I need to do some testing myself on this soon.

Its obvious that flourescents might not produce the same IR that tungstun but that is only a very limited solution for most people. Though for now might be something to keep in mind if you have an important shoot that you have the ability to shoot with flos.

Lenny Levy

Piotr Wozniacki · February 28th, 2009, 02:17 PM

Lenny,

No problem with talking down to me at all :)

I probably wasn't clear enough, but I do realize the middle 2 grabs posted above (at 3200K preset) are too warm due MAINLY to bad WB, not IR contamination. Basically, the left 3 grabs are without any filtering, while the 3 to the right - with some Hot Mirror filter I'm testing now (which only has none to mild effect, BTW).

If I discussed the 3200K preset vs 2700K measured CT with Serena has been because, in fact, I started worrying about my unit's WB presets being off - without any connection to the IR contamination.

Your post, however, helped me stop worrying as indeed, 3200K is more for a direct halogen light, and my shots were taken under regular home tungsten (plus red curtains in the window to block daylight). So, the 2700K is absolutely a more realistic figure for the true CT here!

Well, I did put a disclaimer in my post above these were very "quick & dirty" tests - but I should have taken more time (and thought) posting them, anyway!

Nevertheless, I think my conclusions still hold true:

- the W+B 486 filter I tested earlier is far more efficient than my currently being tested one, as it can get rid of all and any red contamination (I deliberately don't call it "IR"), but sadly is unacceptable due to the greenish vignetting at wide angles

- proper WB is essential for minimizing the red contamination, with a filter as well as without one

I guess you can agree :)

February 27th, 2009, 04:50 PM	#83
Tip McPartland Major Player Join Date: Nov 2005 Location: Crestline, California Posts: 351	Whate balance idea... I'm sure everyone's white balanced through 1/8 or 1/4 CTB to warm up their subjects. I used to do this and sometimes I would also add 1/8 green, can't remember the exact gel. I started doing this when I would have to shoot with existing fluorescent lights, but then I came to think a little less green was good for skin tones much of the time. What occors to me is that perhaps a gel or combination of gels the same color as the fringing, or as close as possible, could be used during the white balance. The result would be a neutral color balance where the vignetting would have been, and a bit less green/cyan in the center where the subject is. This might look nice, or at least nicer than a bias in portions of the picture toward the green side. Tip McPartland

February 27th, 2009, 06:47 PM	#84
Serena Steuart Major Player Join Date: Jun 2006 Location: Studio Alnitak, Melbourne, Victoria, Australia Posts: 640 Images: 3	Generally outdoors I do not use any additional IR filtering (while Bob uses it as default), but it isn't true to say that the IR problem isn't present under 5600K lighting. Attached are two recorded in sunlight (white balanced internal camera ND filters) and the black artificial fibre is recorded black only with the BW486 filter. Also, when suggesting that the default 3200K setting is too hot (which I haven't checked, I always WB) how was the colour temperature of the lights measured? Maybe they were not 3200K. Attached Thumbnails

February 28th, 2009, 02:17 PM	#90
Piotr Wozniacki Inner Circle Join Date: Aug 2006 Location: Poland Posts: 4,086	Lenny, No problem with talking down to me at all :) I probably wasn't clear enough, but I do realize the middle 2 grabs posted above (at 3200K preset) are too warm due MAINLY to bad WB, not IR contamination. Basically, the left 3 grabs are without any filtering, while the 3 to the right - with some Hot Mirror filter I'm testing now (which only has none to mild effect, BTW). If I discussed the 3200K preset vs 2700K measured CT with Serena has been because, in fact, I started worrying about my unit's WB presets being off - without any connection to the IR contamination. Your post, however, helped me stop worrying as indeed, 3200K is more for a direct halogen light, and my shots were taken under regular home tungsten (plus red curtains in the window to block daylight). So, the 2700K is absolutely a more realistic figure for the true CT here! Well, I did put a disclaimer in my post above these were very "quick & dirty" tests - but I should have taken more time (and thought) posting them, anyway! Nevertheless, I think my conclusions still hold true: - the W+B 486 filter I tested earlier is far more efficient than my currently being tested one, as it can get rid of all and any red contamination (I deliberately don't call it "IR"), but sadly is unacceptable due to the greenish vignetting at wide angles - proper WB is essential for minimizing the red contamination, with a filter as well as without one I guess you can agree :) __________________ Sony PXW-FS7 \| DaVinci Resolve Studio; Magix Vegas Pro; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; Decklink 4K Extreme 12G; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive Last edited by Piotr Wozniacki; March 1st, 2009 at 03:44 AM.

February 27th, 2009, 06:06 AM	#76
Brian Cassar Major Player Join Date: Jan 2007 Location: Malta Posts: 306	This twist in this issue is very interesting but confusing as well. I cannot understand why in the test only ND IR cut filters were used. The problem is more accentuated under halogen lights than when filming in broad daylight. So any loss of light due to ND filter is unacceptable especially when shooting under available light (and not controlled lighting). Can someone explain whether these Tiffen ND IR filters can be produced without the ND component in them - just IR cut only? Or is it not possible to have an IR cut filter which works well without some ND inside it? The 486 does not have any ND but then again it does not work well. Piotr I have to disagree also with you on point No.4. I used to say the same thing like you said but after receiving my new Zylight 90 just yesterday I will not use any halogen on-board light again. The Zylight 90 is the LED lamp to use for ENG. It's true that it is very expensive (it took me a year to decide to buy it) but the ability to switch the colour temp at the touch of a button without using any light reducing coloured gels in front of the led's is fantastic. I haven't used it in an assignment but from the tests I did yesterday it's absolutely amazing! I bought it specifically to eliminate the halogen light on board of the EX3 which was causing too much contamination.

February 27th, 2009, 03:15 PM	#80
Brian Cassar Major Player Join Date: Jan 2007 Location: Malta Posts: 306	I think I found a temporary solution to this IR contamination problem. As I had indicated before I tend to film a lot under available light (without any fill in light) which on most time is predominantly halogen. This was obviously giving me loads of problems with black material. I have just done a very quick test - I filmed a black t-shirt under available halogen light. This as expected turned to a brownish tint. I then switched on the newly bought Zylight 90 and since this is LED light the black t-shirt was restored immediately back to black! Even when I had dimmed the light to almost minimum, as long as a very small quantity of LED type of light fell on the black fabric, the problem disappeared (without the use of any filter). Please note that the Zylight was switched on the 3200K setting so as not to disrupt the white balance that had been set to the prevailing halogen light. This means that unfortunately I have to change my style of filming and start using some dimmed fill-in LED light whenever there is halogen light as the main source of lighting. As I said this was a very quick test. I have yet to test it out in a proper shoot - but I'm expecting the same type of results that I had obtained today.

February 28th, 2009, 05:50 AM	#88
Serena Steuart Major Player Join Date: Jun 2006 Location: Studio Alnitak, Melbourne, Victoria, Australia Posts: 640 Images: 3	The difficulty with tungsten is that the colour temperature is quite sensitive to lamp voltage and age, so we can't be really sure about its colour temperature without measuring (hence the colour temperature meter). You can measure the voltage when the lamp is on and if that matches the designated lamp voltage then you won't be far out. Our supply here, for example, is supposed to be 230v AC, but varies between 220 and 245 (depending on district load) and I have seen it below 210. Stage lighting is generally on dimmers, so the CT can vary quite a bit across the stage and in time. Today I did run a test using a RedHead QI and the camera WB, 3200 preset and colour temp meter all agreed within +/-100K . The EX1 WB gave me 3100K and I couldn't see the difference switching to the preset. The thing is to make sure all cameras match in their settings, because matching in post is a pain. You can, as you know, pre-set any CT you find appropriate, so the 3200 factory pre-set isn't operationally critical.

February 28th, 2009, 01:21 PM	#89
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	Piotr, I'm having trouble identifying exactly what problem your having because I don't know what lights you were using or for that matter how much background you may be bringing to your understanding. Please excuse me if it sounds like I'm talking down here. It looks like you you shot the test of the chair under ordinary household tungstun bulbs which are not 3200 but closer to 2600- 2900K so of course the picture would appear red. Alternatively Serena is right that if your voltage is lower than what even professional photo lamps are rated for (usually 3200) the same thing would happen. This has nothing at all to do with IR contamination, just ordinary white balance and color temperature. IR is something that only affects some fabrics in an otherwise well color balanced shot. It is interesting though that people with the EX on these boards have been complaining mostly about IR under Tungstun light rather than in daylight while using ND while complaints about the RED seem to center more about ND problems. I need to do some testing myself on this soon. Its obvious that flourescents might not produce the same IR that tungstun but that is only a very limited solution for most people. Though for now might be something to keep in mind if you have an important shoot that you have the ability to shoot with flos. Lenny Levy