IR ND for BMPCC

I've been looking into getting an IR ND filter for exteriors. I've seen the Abel Cine videos about this and how every sensor is slightly different. Has anyone tested the various IR ND filters with the Pocket Camera?

I've been looking at the Tiffen ND IR filters and there are two variations: Hot Mirror and Water White. I don't know which might work better without purchasing and trying them myself.

Any thoughts?

Thanks.

I have the Tiffen T1 IR Filter Water White. I want to note it does correct colors from IR destruction but If you have a screw on ND Variable filter you can not put the this IR behind it because it has no threads to screw anything into. I just order a step down ring for my ND filter because it's 82mm and my IR filter is 72mm so I'm going to try putting the IR in front of the ND tomorrow.

Thanks for the info Mark. I'll be using a matte box with a 4x4 filter so I won't have that issue.

I have a .3, .9, 1.2 IRND Tiffen water white 4X4's and a 4X4 circular Pola. I have yet to find a situation where a combination of 2 of these wasn't enough. And I use them on either my Sony F3, BMCC and pocket camera. But I also don't shoot WFO in most cases.

I was sent a technical paper by a sales rep from Tiffen when I was inquiring about similar questions. Apparently the best combination is a hot mirror and ir cut together, either in the form of a separate hot mirror as the outer most element, along with an irnd. You can stack regular ND's for greater light reduction but you should not stack ir nd's, (although you can put an ir nd in combination with stacked regular ND's. What Tiffen refers to as their T1 filter has very specific range values of far red it affects.

It is all explained in the following paper. I will have to upload it in two installments in order to display all of the graphs:


THE TIFFEN HOT MIRROR INFRA-RED NEUTRAL DENSITY STORY
PROLOG:
In today’s motion picture and television market we are seeing an increased use of Digital Motion Picture Cameras. Along with that increase is an increased need for higher grade neutral density filters. However with this combination, a significant issue has come to light (pardon the pun). This issue has been referred to as IR pollution or contamination which steals contrast and color. It occurs in the near infra-red and infra-red portion of the spectrum and must be eliminated completely in order for the cinematographer’s creative vision to be realized. This can only be done using a combination of infra-red blocking agents. Some of these Camera’s have built in partial solutions, others do not. In either case, TIFFEN with over 70 years of experience and two Academy Awards for technical achievement have solved this problem. Below is the story of how this is done. Be aware – It’s a little graphic!


FORESHADOW:
• There is only one complete solution to IR Pollution: The TIFFEN Hot Mirror Infra-Red Neutral Density Combination Filter (or stacking a TIFFEN Hot Mirror and a TIFFEN IRND Filter).

TIFFEN Hot Mirror Infra-Red Neutral Density 0.90 Combination FilterTransmission curve

0.90 Combination Filter Transmission curve .jpg (29.57 KiB) Viewed 8882 times

ACT ONE SCENE ONE:

ENTER NEUTRAL DENSITY (ND) 0.90
• ND Filters for years have been an extremely important tool for cinematographers to manipulate visible light.
• An ND 0.90 or 3-stop Filter (graph below) transmits 12.5% of the Visible Spectrum Light, but in the near infra-red transmission increases and creates an imbalance. (Enter IR Pollution/Contamination).
• There exists a wide range of ND filters: ND 0.30 (or 1-stop) - Transmits 50% of the visible spectrum light – creates minimal IR Pollution, to ND 2.1 (7-stop) - Transmits 0.78% of the visible spectrum light – results in significant IR Pollution.

ND 9 filter curve.jpg (30.67 KiB) Viewed 8882 times

ACT ONE SCENE TWO:

ENTER A TIFFEN HOT MIRROR FILTER:
• The TIFFEN Hot Mirror Filter Transmits essentially all visible spectrum light, and blocks Infra-Red Light.
• Some Digital Motion Picture Cameras have this filter built into their unit. Those that don’t need to add it in order to eliminate the non-image forming Infra-Red Light (IR Pollution).

Hot Mirror transmission.jpg (21.64 KiB) Viewed 8882 times

ACT ONE SCENE THREE:

PLACE A TIFFEN ND 0.90 PLUS A TIFFEN HOT MIRROR INTO YOUR MATT BOX
• The transmission in the visible spectrum remains essentially unchanged
• The Infra-Red Transmission (IR Pollution) is blocked.
• Notice the “spike” at the end of the Visible Spectrum in the near Infra-Red. The ND and Hot Mirror filters alone do not completely block these light waves. This gap results in an unwanted color shift, greens become reddish muddy browns and/or blacks become purplish.

ND9 plus hot mirror.jpg (33.54 KiB) Viewed 8880 times

____________________________________________________________________________________

ACT TWO SCENE ONE:

ENTER TIFFEN IRND 0.90:
• The TIFFEN IRND extends the light transmission characteristics of the TIFFEN ND 0.90 into the Infra-Red region of the spectrum
• For those Digital Motion Picture Cameras that have the Hot Mirror filter built into their unit, this filter will eliminate the near Infra-Red color shift that occurs (particularly when using greater density ND’s).

IRND9.jpg (33.15 KiB) Viewed 8880 times

ACT TWO SCENE TWO:

ENTER TIFFEN Hot Mirror (HM) IRND 0.90 Combination Filter
• Creates an overlap in the near Infra-Red to Infra-Red portion of the spectrum.
• Virtually eliminates all non visible spectrum light, making sure that the Digital Imaging Sensor “see’s” and “Records” your vision.
• Uses only one stage in the Matt Box (Note: The same effect can be achieved stacking a TIFFEN Hot Mirror and TIFFEN IRND Filter using two stages of the Matt Box)

IRND9 plus Hot mirror.jpg (31.09 KiB) Viewed 8880 times

____________________________________________________________________________________

EPILOG:

• TIFFEN Hot Mirror Filters are essential for the cinematographer using a Digital Motion Picture Camera that does not have this feature built into the unit.
• TIFFEN Infra-Red Neutral Density IRND Filters are essential for the cinematographer using a Digital Motion Picture Camera to control the near Infra-Red light, particularly when using heavier grades of ND’s.
o IMPORTANT NOTE: The IR component of a TIFFEN IRND is balanced with each ND component to assure accurate color reproduction.
• The complete solution to IR Pollution is a combination of the TIFFEN Hot Mirror and TIFFEN Infra-Red Neutral Density IRND Filter. The cinematographer can combine them by stacking in the Matt Box or by using a single New TIFFEN Hot Mirror Infra-Red Neutral Density Combination filter (requires only one stage in the Matt Box).
• TIFFEN Hot Mirror, TIFFEN IRND, and TIFFEN Hot Mirror IRND Filters are made from optically pure water white glass and will be available in May/June 2008 in sizes: 4 x 4, 4 x 5.650, 5.65 x 5.65, 138, and 105C.
• Best of all TIFFEN’s Hot Mirror (HM) and Hot Mirror IRND’s (HMIRND) are manufactured using our proprietary lamination process, which means that each effect is captured (protected) between two pieces of glass, allowing us to grind and polish both surfaces to achieve perfect parallelism. For the cinematographer, this means worry free handling. They can be cleaned as often as you like and you don’t have to be concerned about scratching the coating that will render your Hot Mirror filter useless.

As an alternate to the above posts, from all of the testing I have done and seen elsewhere, Vari ND's are far more neutral in the way they transmit light and affect IR pollution. I suspect they do not cut out the same amount of ultra violet and therefore on a relative basis don't bombard the sensor with pure IR pollution.

Look at this series of tests done with the Alexa...pay special attention at the very end of the video when they show vari nd's for comparison.



This agrees with what I have found in my own testing. I am still doing further testing because this info applies only to the color shift to red (particularly seen in black synthetics) introduced by IR pollution...not the other color shifts the polarization and tinting (usually green) a Vari ND might introduce.

I am planning to test my vari nd by itself, combined with just a hot mirror, and combined with a hot mirror and T1 filter to see what the differences are. When I get a chance to complete it I will post my results.

http://nofilmschool.com/2012/12/choosin ... -infrared/

Thank you everyone who responded. Lots of good info here.

Thanks for the info Mark. I'll be using a matte box with a 4x4 filter so I won't have that issue.

I'm still comparing some so I can order one, just don't know if i'll need one with a rotating filter holder yet but might just buy one with it so I don't have to upgrade later

I'm still comparing some so I can order one, just don't know if i'll need one with a rotating filter holder yet but might just buy one with it so I don't have to upgrade later

If you want to take full advantage of a circular pola at any point you'll need a rotating stage.