F3 Hot Mirror - Infrared issues - Maroon/Black issue - Tiffen IR ND Filter ?

H

HD Studio Belgium

Well-known member
Has anybody done a comparison between the F3 and the F35 or even the EX3 on Infrared contamination? Does the built in Hot Mirror cut to 680 nm or is it again limited to 700nm and causes the known maroon casting on black (cotton)? In a few comparison tests I did between the EX3 and the F3 under the same light conditions (indoors) the F3 seems to cut off perfectly while the EX3 goes 'maroon'. My question is ... has anybody seen the IR pollution problem under certain light/fabric conditions on the F3 or is this camera indeed 'clean' as I seem to find out? There seems to be no need for a T1 or an IRND filter ...

Updated on March 19 ... this article seem to have disappointing results ...

http://provideocoalition.com/index.php/awilt/story/ag-af100_and_pmw-f3_on_the_charts/P0/
 
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Haven't got my F3 yet, but just to note the conditions my EX3 shows far red. It's not IR. With very dark or black synthetics when using heavy ND outdoors, or under tungsten indoors. Cotton does not exhibit this, only synthetics.
 
Very overcast day today here 'in Bruges' ... that's in Belgium. So can't test the outdoor ND influence ... but indoor ... the EX3 on a preset 2400 K and the F3 on the same 2400 K ... it is dramatic to see the EX3 go completely 'maroon' on certain black fabric and the F3 is as clean as can be ... I wonder if the same positive result will happen in strong outdoor light and heavy ND filter. (I mean the built in ones) ... so far a very positive result !
 
Sony dealt with the far red or infrared contamination issue in the EX1R. If you spend some time doing a search through EX forums, not just this one, you will find a lot of time was spent on this issue and Sony nailed the problem in the EX1R. A few tests have come out that I have read on the F3 torture testing it for IR contamination and no one has been able to reproduce the issue.
 
Thanks, Didn't know the issue was addressed and solved with the EX1R. ... So ... the outcome of my personal little 'messing around' was at least 'technically' correct in its findings ...
Good to know there should be no bad surprises then 'torturing' it further. :)
 
I haven't seen any IR issues yet with built in NDs.

Because of this, I might elect to use the built-ins more often than I would
 
HD Studio Belgium said:
Very overcast day today here 'in Bruges' ... that's in Belgium. So can't test the outdoor ND influence ... but indoor ... the EX3 on a preset 2400 K and the F3 on the same 2400 K ... it is dramatic to see the EX3 go completely 'maroon' on certain black fabric and the F3 is as clean as can be ... I wonder if the same positive result will happen in strong outdoor light and heavy ND filter. (I mean the built in ones) ... so far a very positive result !
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Favorite vacation spot for hitmen from all over the world:happy:
 
Most digital cameras need a hot mirror. The RED was the worst. (seems they fixed the IR issue) Perhaps a F3R will have a hot mirror built in. IR contamination happens when you use high levels of ND in bright light, as opposed to stopping down the lens. Standard ND, only cuts the visible spectrum. Using the ND "2" position on th camera a 4 stop ND filter, reduces visible light by 4 stops but does not cut any of the Infrared in daylight. so you get 4 stops of IR "over exposure" which shows up in the blacks. Its practically impossible to Color Correct out. I need to go pick up a Hot mirror. The last one i bought got damaged on the job.
 
Hi Timur, if you say you'll pick up a Hot mirror ... you mean a specific Tiffen filter ? I am reading about these IRND's from Tiffen and a T1 filter ?
Does that solve my problem?
 
It doesn't only happen in daylight though. It will also happen with tungsten lights. IR is basically heat, and tungsten lights give off tons and tons of heat, so they're far more likely to cause IR pollution than an HMI or fluo would.
 
Oh but it does. At least it did on red. You had to ND w/ a hot mirror other wise blak was a muddy burgundy.

I'll test iit out.
 
I don't think you read it right -- I'm saying that the IR issue happens under daylight, yes, if there's enough ND filtration. But it *also* happens under tungsten, and in the case of tungsten ND doesn't matter.

The reason it happens in daylight is, like you said -- the ND cuts the visible light but it doesn't cut the heat (IR) so the proportion of heat to light rises. Under tungsten, tungsten lights are already torching 80% of their energy as heat and only 20% as light, so they're veritable IR cannons.

It happens under both circumstances.
 
Barry_Green said:
I don't think you read it right -- I'm saying that the IR issue happens under daylight, yes, if there's enough ND filtration. But it *also* happens under tungsten, and in the case of tungsten ND doesn't matter.

The reason it happens in daylight is, like you said -- the ND cuts the visible light but it doesn't cut the heat (IR) so the proportion of heat to light rises. Under tungsten, tungsten lights are already torching 80% of their energy as heat and only 20% as light, so they're veritable IR cannons.

It happens under both circumstances.
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We shouldn't confuse heat with IR. Heat is transitional energy, IR is a spectrum of light.
While you can make correlations between heat and IR under certain applications, there is little correlation between thermal radiation and the spectrum of light that the F3 CMOS sensor picks up. IR is attributed to less than half of the heating energy from the sun, the rest comes from visible light, and the reason that tungsten lights has more IR issues is because it uses dichroic glass coating; which is designed to reflect IR.

As far as the IR issues with the F3 compared to the EX1R, there is a technical reason for this. IR filters produce blue fringing on the edges of the filter as the filter/sensor size grows. This is largely due to the level of telecentricity at the edges of the filter.

For a camera with a smaller sensor, such as the EX1R, a stronger IR filter can be applied as fringing issues aren't a problem as light hitting the sensor is more parallel as it passes through the IR filter. However, a larger sensor cameras blue fringing becomes an issue, particularly for wider lenses. So there is this trade off between what level of IR filter to apply relative to the size of the sensor and other negative image aberrations.
 
Would this all mean that the T1 filter and IRND filters from Tiffen that seem to have solved the problem for the original EX1 and EX3, might, because of the bigger sensor in the F3, not work?
I am about to order a set of Tiffen IRND ... would like to know if they will not cause your 'blue fringing' before I shelve out 900 Euro ...

These are the Tiffen links ... http://www.tiffen.com/userimages/T1_IR_Charts_SS.pdf http://www.tiffen.com/press_release_T1IR_filter.html
and http://www.tiffen.com/artadams.html

This is a very acute bit of trouble for me as I am about to multi camera a series of classic music performances ... over a hundred people dressed in different 'black' outfits ... this might end as Maroon 100 :) I start to understand why a few people 'wished me luck' with the contract. I have nothing else than EX3 and F3 cameras ...
 
HD Studio Belgium said:
Would this all mean that the T1 filter and IRND filters from Tiffen that seem to have solved the problem for the original EX1 and EX3, might, because of the bigger sensor in the F3, not work?
I am about to order a set of Tiffen IRND ... would like to know if they will not cause your 'blue fringing' before I shelve out 900 Euro ...

These are the Tiffen links ... http://www.tiffen.com/userimages/T1_IR_Charts_SS.pdf http://www.tiffen.com/press_release_T1IR_filter.html
and http://www.tiffen.com/artadams.html

This is a very acute bit of trouble for me as I am about to multi camera a series of classic music performances ... over a hundred people dressed in different 'black' outfits ... this might end as Maroon 100 :) I start to understand why a few people 'wished me luck' with the contract. I have nothing else than EX3 and F3 cameras ...
Click to expand...

It should work, sensor size and IR filter are relative to where the filter is placed. The blue fringing issues I've mentioned are usually more of an issue for absorptive IR cut-off filters that are placed on the CMOS sensor directly (CCDs tend to use reflective IR filters). If the filter is on the lens then light entering the filter should be less susceptible to blue fringing compared to a filter on the sensor since the filter itself is placed further away from the sensor. And keep in mind, blue fringing is usually only an issue as the lens gets wider, the better cinema lenses, that have better telecentricity, suffer less from this.
 
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