How to reduce the nd filter warm color cast?

[Marsu42]

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!

[neuroanatomist]

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

[GMCPhotographics]

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.

[wayno]

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.

[Menace]

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

[bluesphoto]

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	Small | Large

And here are some alternatives: http://www.udel.edu/cookbook/class/Tricks/color-cast.pdf and http://www.photoshopessentials.com/photo-editing/photo-filter/

[Marsu42]

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

[bluesphoto]

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.

[EOBeav]

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. "

[GMCPhotographics]

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. "

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.

[pwp]

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

[paul13walnut5]

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.

[Marsu42]

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.

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.

[RLPhoto]

Buy LEE or schnider optic.

[Marsu42]

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).