# How to reduce the nd filter warm color cast?



## Marsu42 (Feb 10, 2013)

I'm about to buy the Heliopan 2093 nd filter with 3.0 density. The manufacturer states (German: http://www.heliopan.de/produkte/graufilter.shtml) that this density produces a warm color cast that can be removed by "adding a Heliopan UV/IR filter in front of the ND filter". 

Now I'm confused: a) all I find are UV *or* IR filters, what is the manufacturer talking about and b) does this work & is it necessary or is it trivial to remove the warm color cast in postprocessing?

Thanks!


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## neuroanatomist (Feb 10, 2013)

The warm tone can be easily removed by adjusting the WB in post. I wouldn't stack another filter to get there...


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## GMCPhotographics (Feb 11, 2013)

Marsu42 said:


> I'm about to buy the Heliopan 2093 nd filter with 3.0 density. The manufacturer states (German: http://www.heliopan.de/produkte/graufilter.shtml) that this density produces a warm color cast that can be removed by "adding a Heliopan UV/IR filter in front of the ND filter".
> 
> Now I'm confused: a) all I find are UV *or* IR filters, what is the manufacturer talking about and b) does this work & is it necessary or is it trivial to remove the warm color cast in postprocessing?
> 
> Thanks!



Sometimes the warm effect can be quite nice. I find the Heliopan warmth to be the most agreable of the ND colour casts. Yes in an ideal world there wouldn't be any....but in reality a little warmth can add a nice effect which is slightly more attractive than dialing it in via WB. I've yet to see an ND filter which doesn't have a colour cast and I've tried a few! 
To remove, shoot raw and use WB select tool and choose a pure white item in the frame. Then tune the WB a little according to your eye and taste.


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## wayno (Feb 11, 2013)

I find the charcoalley cast from my Hoya ND400 9 stop to be actually rather challenging to correct for. To deal with the tone it imparts, it's more than just WB. It's not unpleasant, just distinct.


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## Menace (Feb 12, 2013)

Personally, not a fan of stacking filters - LR to fix warmth


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## bluesphoto (Feb 12, 2013)

You can fix it with the white balance.
Or you can do it in photoshop with a method that can remove every colour cast ( doesn't always work well because it is based on the average of the image). 
this is the one I use: Photoshop Quick Colour Cast Removal Technique
And here are some alternatives: http://www.udel.edu/cookbook/class/Tricks/color-cast.pdf and http://www.photoshopessentials.com/photo-editing/photo-filter/


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## Marsu42 (Feb 13, 2013)

bluesphoto said:


> You can fix it with the white balance.
> Or you can do it in photoshop with a method that can remove every colour cast ( doesn't always work well because it is based on the average of the image).



Thanks a lot for the advice! I ordered the Heliopan filter today and am very eager to see the results, and I admit I hope that wb will fix it most of the time because with Photoshop I end up with a 100mb tif instead of a 20mb dng :-o


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## bluesphoto (Feb 13, 2013)

Marsu42 said:


> Thanks a lot for the advice! I ordered the Heliopan filter today and am very eager to see the results, and I admit I hope that wb will fix it most of the time because with Photoshop I end up with a 100mb tif instead of a 20mb dng :-o



Wb can fix it but I personally alway fix it in ps because then you can work in layers because sometimes the colour cast is higher(more noticeable) in certain regions than in others so then you have to use masks.
And there is also the fact that white-balance only checks if the whites are white it doesn't necessary mean that the other colours are good after correcting wb. 
Which most of the time they aren't(if you stack) because the nd's give a stronger colour cast.


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## EOBeav (Feb 15, 2013)

Marsu42 said:


> I'm about to buy the Heliopan 2093 nd filter with 3.0 density. The manufacturer states (German: http://www.heliopan.de/produkte/graufilter.shtml) that this density produces a warm color cast that can be removed by "adding a Heliopan UV/IR filter in front of the ND filter".



Now that's quite a marketing ploy. "This is a great filter, but it creates some unwanted colorcast, so buy this other filter we make to fix it. "


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## GMCPhotographics (Feb 15, 2013)

EOBeav said:


> Marsu42 said:
> 
> 
> > I'm about to buy the Heliopan 2093 nd filter with 3.0 density. The manufacturer states (German: http://www.heliopan.de/produkte/graufilter.shtml) that this density produces a warm color cast that can be removed by "adding a Heliopan UV/IR filter in front of the ND filter".
> ...



Yep, I don't belive in this either. I've read a few sites claiming that IR is the cause for ND colour casts...and yet I can see the same colour cast through the filter when held up in front of my eye. I have an IR cut filter (not from this particaulr brand) and no it makes no discearnable difference. Most DSLRs have a strong IR cut filter built it to the AA filter layer over the sensor. ND colour casts are a fact of life unfortunatly, so the trick is to find one which has a pleasant colour cast. When I spoke to Lee about this a long time ago, I was told that the dyes used are approximations of a linear light density reduction. no one dye can cut light across the whole colour spectrum and multiple dyes are needed to cover the whole range. These dyes aren't linear either, each dye has a curve and these are selected to approximate a neutral density. Multiple curves from multiple dyes causes overlaps and voids in the tonal responce curve, in reality the curve is quite wobbly and bumpy. 

it reminds me of a quote from the late Douglas Adams "Science is what we dream of, Technology is what we get stuck with. then asked what defines technoligy, Douglas repsonded...that's easy....does it need a manual". 
WB is not enough to correct a colour cast, becuase the cast isn't linear across the colour spectrum. WB will only give an approximation or averaged correction.


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## pwp (Feb 15, 2013)

Marsu42 said:


> Now I'm confused: a) all I find are UV *or* IR filters, what is the manufacturer talking about and b) does this work & is it necessary or is it trivial to remove the warm color cast in post-processing?


It's only non-trivial if you shoot JPEG. If you're shooting RAW you have _full_ control over colour in PP. 

-PW


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## paul13walnut5 (Feb 15, 2013)

I've found it hard to eradicate entirely (I'm using the B+W 3.0 which has a strong amber cast) even with things like a qp card or grey card done in a test shot first.

I compensate WB in camera, adding in around 3000k over what a scene would usually be. This looks fairly close on the LCD, take a test shot with known colours (grey or QP, may need to up the ISO, open the aperture for practicality, I suppose you could do a manual WB instead here, if you have a neutral target)

You can shifty the WB slider at the RAW stage too, but I think there are secondary spectrums at work that means there is no magic bullet solution.


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## Marsu42 (Feb 15, 2013)

pwp said:


> Marsu42 said:
> 
> 
> > Now I'm confused: a) all I find are UV *or* IR filters, what is the manufacturer talking about and b) does this work & is it necessary or is it trivial to remove the warm color cast in post-processing?
> ...



True and I shoot raw, but as paul13walnut5 full control doesn't mean easy control if it's not something that clearly falls into the wb or color slider category - so if each picture would need individual treatment it'd be easier to fix the problem while shooting with another stacked filter as the manufacturer suggests.

But from what I read, wb usually does the trick esp. if nobody knows how the real scene looked - my filter just arrived and I'll see this weekend how I can handle the color shift.


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## RLPhoto (Feb 15, 2013)

Buy LEE or schnider optic.


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## Marsu42 (Feb 15, 2013)

RLPhoto said:


> Buy LEE or schnider optic.



If you're talking about schnEider :-> optics (B+W) - they are just releasing their 82mm nd filters, they much more expensive than Heliopan (probably early adopter's premium) and one of the above posts also states that b+w also has a color cast - so I went for the cheaper Heliopan w/o coating (it's not supposed to let through light after all).


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## RLPhoto (Feb 15, 2013)

Marsu42 said:


> RLPhoto said:
> 
> 
> > Buy LEE or schnider optic.
> ...



I haven't noticed a 3000K shift in color with any of my B&W filters. Even my old cheapo colkin ND filters aren't that terrible, but then again I'm using the Pro-glass LEE and Schneider 4X4 & 4X6 GND & ND square filters. 

You might want to look into a square system, Its fantastic.


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## neuroanatomist (Feb 15, 2013)

Marsu42 said:


> RLPhoto said:
> 
> 
> > Buy LEE or schnider optic.
> ...


Schneider has had an 82mm 10-stop ND for a while (in fact, when I bought it in 2011 they were the only game in town for an 82mm ND3.0 screw-in). It does have a warming effect, you can see an example I posted in this thread.


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## paul13walnut5 (Feb 15, 2013)

RLPhoto said:


> I haven't noticed a 3000K shift in color with any of my B&W filters. Even my old cheapo colkin ND filters aren't that terrible, but then again I'm using the Pro-glass LEE and Schneider 4X4 & 4X6 GND & ND square filters.
> 
> You might want to look into a square system, Its fantastic.



In hindsight I should have went the big stopper route, though to be fair, the B+W was hardly a budget option.

I'm interested in the 3.0 filters you've used made by cokin, can't find these anywhere?
Had a look for the Schneider 3.0 filters as well, having bother finding them, other than as being sold under the sister B+W brand. I could find the Schneider square filters at up to 1.8 ND, but not as high as 3.0.

Just interested in the comparison you've made between the colour shift on my B+W 3.0 (N.B. 1000 NDx, 10 stop, not 3 stop) and the similar cokin and schneider filters you've used. 

Can you give me a link to the Cokin 3.0 ND (1000x, 10 stop) filter? If they are as cast free as you say then I might end up getting one.


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## RLPhoto (Feb 15, 2013)

paul13walnut5 said:


> RLPhoto said:
> 
> 
> > I haven't noticed a 3000K shift in color with any of my B&W filters. Even my old cheapo colkin ND filters aren't that terrible, but then again I'm using the Pro-glass LEE and Schneider 4X4 & 4X6 GND & ND square filters.
> ...



The Big stopper is my only 10-stop ND, I haven't used it more than twice compared to my GND's. Haven't seen a 3000K color cast but perhaps more like 500K cooler.

Colkin and Schneider don't make ND's that dark but on the ones I do own, a 3000K shift I haven't seen but I've only had the .3-.6-.9 filters GND's before I ditched Colkin all together.

IE: My fav's.

http://www.bhphotovideo.com/c/product/399443-REG/Schneider_68050656_4x5_65_Graduated_Neutral_Density.html

http://www.bhphotovideo.com/c/product/399272-REG/Schneider_68_056412_4x4_Neutral_Density_1_2.html

http://www.bhphotovideo.com/c/product/686370-REG/LEE_Filters_10_STOP_GLASS_4X4_4_x_4_Big.html


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## Marsu42 (Feb 16, 2013)

neuroanatomist said:


> Schneider has had an 82mm 10-stop ND for a while (in fact, when I bought it in 2011 they were the only game in town for an 82mm ND3.0 screw-in).


Ok, in this case I was unable to find it for sale anywhere or simply forgot about it after seeing the price :-o

But concerning the original topic: I just stumbled across a link about "*IR Pollution*" that doesn't just result in a color cast but lower contrast, and this is said to be fixable with a combined ir/uv stop filter: http://www.leeduguid.com.au/blog/tips/bw-10-stop-nd-filter-nd-110/

However, this filter has a big drawback: "Interference filters do not work well with wide angle lenses; light rays entering at an angle cause differing color rendition, resulting in increasingly cyan corners. It should not be used on lenses with an angle of view wider than 60° (about 35mm on a full-frame 36 X 24mm sensor)."


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## brad goda (Feb 16, 2013)

like "hot mirror NDIR filters"


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## brad goda (Feb 16, 2013)

use Fuji ND filter behind the lens.


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## brad goda (Feb 16, 2013)

yah they are expensive... 
Fujifilm made an extensive selection of durable wratten filters in 100mm size... lasted longer than the kodak filters but thin and flexible unlike Sinar acrylic 100mm filters... I know I have a full ND kit within my old filter kit... yah a whole pelican case full of blue yellow magenta cyan grads with holders from the good ol days ... like hundreds of dollars hand over fist of filters... glad my assist insisted NOT ebaying the case... 

anyways if you can find fuji IR and ND maybe in Japan or EU... I am sure you can sandwich them together behind the lens...
should help with IR funk with ND but dont know about CA... UWA does create problems...

beginning of Digital we used to add blue 82, 80A 80B filters to take sensors into tungsten range...
we thought it was better than just pushing a button... how things have come so far... there are buttons for everything...(better blue sensitivity or overall better)
the old fisheye had internal filters... maybe canon will have to bring back something like this one day...


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## Marsu42 (Feb 16, 2013)

brad goda said:


> like "hot mirror NDIR filters"
> use Fuji ND filter behind the lens.



Thanks for the information - these two pieces (hot mirror + gelatin nd) seem to be a solution for my 17-40L and the combined ndir for other lenses - though both outside my current budget. So I'll see how the "plain" 3.0 nd filter performs in the summer with more ir radiation - but good to know what the alternatives are, but the ir polution really seems to be an issue: http://www.tiffen.com/press_release_Hot_Mirror_IRND.htm

Btw: This page has a good discussion on fixed/vari nd filters concerning ir & uv leakage: http://www.dpreview.com/news/2011/8/12/heliopan82mmnd 



> Magenta casts and ND filters are usually due to IR leakage in the filter. This is common, most strong filters let a lot of IR through, and most older cameras register that IR in the blue and red channels, making magenta. A good "hot mirror" IR filter should clear it right up. And it will improve your foliage colors, too.





> Every camera responds differently to variable ND filters (crossed polarizers, whether you cross your own or use something like the Heliopan) and also to actual ND filters. ND filters "leak" a lot of IR light. That's why crossed polarizers are sometimes used as improvised IR filters. Crossed polarizers have an additional problems that a "normal" ND filter, a single piece of dyed glass, won't have, in that they also leak UV. Cameras have good IR/UV blocking filters inside, but when you do something like blocking 8 stops of visible light, the leaked UV and IR start to cause problems. IR typically shows as a magenta cast, UV as a blue cast.


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## neuroanatomist (Feb 16, 2013)

Doesn't have to be IR. if you look at the transmission curve for the B+W 3.0, it starts to rise from 'neutral' at about 630nm.


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## Marsu42 (Feb 16, 2013)

neuroanatomist said:


> Doesn't have to be IR. if you look at the transmission curve for the B+W 3.0, it starts to rise from 'neutral' at about 630nm.



Um, is this the same with the Heliopan filter (I couldn't find the information through google, and the manufacturer seems to think otherwise)?

And if I understand you correctly you're saying "IR Polltution" cannot be a problem for these nd filters no matter the fuss about it :-o ? I'm asking because the websites I just read suggest that nd filters leak ir on long exposure shots no matter how the transmission curve is supposed to be, and the only and new (see tiffen 2008 press release) solution is a hot mirror filter.


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## brad goda (Feb 16, 2013)

neuroanatomist said:


> Doesn't have to be IR. if you look at the transmission curve for the B+W 3.0, it starts to rise from 'neutral' at about 630nm.



ok whatever you say but cinema guys I know all have full line up of hot mirror IR ND filter kits.
I guess they have spent thousands for nothing.

what do i know... live and learn


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## brad goda (Feb 16, 2013)

marsu42
ok good you are finding the info to answer your problem! great info hunting!


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## neuroanatomist (Feb 16, 2013)

brad goda said:


> neuroanatomist said:
> 
> 
> > Doesn't have to be IR. if you look at the transmission curve for the B+W 3.0, it starts to rise from 'neutral' at about 630nm.
> ...



Ummm...ok. :-\ My point was that it's important to know the transmission characteristics of your filter. With a B+W 110 and an IR cut filter starting at 700nm, you've still got some increased transmission from 630-700nm.


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## Marsu42 (Feb 16, 2013)

brad goda said:


> marsu42
> ok good you are finding the info to answer your problem! great info hunting!



Thanks  and maybe no surprise the manufacturer doesn't say: shooting with this filter will generate a color cast and lower contrast in high ir conditions, but you have to pay a *lot* more for the solution that fixes it and our stacked solution won't work for wide angle lenses at all so go and look elsewhere :-o


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## brad goda (Feb 16, 2013)

neuro
got your point... 
but in IR yes you do need to know transmission freq. near IR or far IR ... UV 
which to block with which filter... 
lucky some filter companies made stackable or all in one hot mirror NDs...

check it out.. this from tiffin...prices not as scary as others

http://www.tiffen.com/press_release_Hot_Mirror_IRND.htm


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## GMCPhotographics (Feb 17, 2013)

RLPhoto said:


> Buy LEE or schnider optic.



Lee had some of the most variability in quality control and colour casts of all the filters I've tried their ND grads often have a purple cast in the darker densities. The B+W cast is very strong and like a copper tone. Very odd and quite harsh. 
Heliopan are my preferred choice and offer more options in their range. I personally find their 5 stop to be the most useful. The Hoya 9 stop has a nice pink hue, which I really like too.


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