Gear Talk > Lenses

How to reduce the nd filter warm color cast?

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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
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:

--- Quote from: bluesphoto on February 12, 2013, 08:11:23 AM ---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).
--- End quote ---

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:

--- Quote from: Marsu42 on February 13, 2013, 04:39:34 AM ---
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

--- End quote ---

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:

--- Quote from: Marsu42 on February 10, 2013, 03:22:20 PM ---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".

--- End quote ---

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:

--- Quote from: EOBeav on February 15, 2013, 12:16:37 AM ---
--- Quote from: Marsu42 on February 10, 2013, 03:22:20 PM ---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".

--- End quote ---

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. "

--- End quote ---

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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