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Colour cast when using filters?
Posted 3 months ago
Can anyone explain why I'm getting a colour cast when I use more than one filter. One filter ie an ND Grad is not a problem but when I stack two I seem to get a red colour cast. For your information I also leave my skylight filter in place permanently so whether this has something to do with it. Also the filters are Hitech, so not cheap things and supposedly a make that didn't suffer from this problem.
It's just proving to be a nuisance as on many occasion one 3 stop grad is insufficient to hold back the light and when I add the second I turn red.
 
gerard sexton  Senior Critic
Posted 3 months ago
Tim it would be interesting to establish why. Though my immediate response is are you shooting in RAW or JPG (or TIFF) & when are you performing a WB check before you put the filters on or afterwards or not at all? But as you say its strange because there is no obvious reason why this should happen.
 
Posted 3 months ago

gerard sexton wrote
Though my immediate response is are you shooting in RAW or JPG (or TIFF) & when are you performing a WB check before you put the filters on or afterwards or not at all?
Hi Gerard
I always shoot in RAW and leave my WB on cloudy. I prefer to (or by habit) stick to a standard WB and if I need to adjust it do so in Lightroom. I also don't use AWB as I often take multiple exposures and worry that I'll end up with different WBs on each shot. Whether that's actually what would happen or not I'm not sure.
 
Guido Brandt  Book editor
Posted 3 months ago
Hi Tim,

I also have the Hitech filters and have noticed the same - unfortunately I think it is a well known problem, to more extent with Cokin filters, less with Hitech and even lesser with Lee ones.
I have read somewhere on the net that it has to due that the different wavelenghts of light are filtered differently with the ND/grads filters.   I have found in the past that the problem is intermittently, which makes me believe it has a lot to do also with the angle of light.
However, in most cases I could fix it with modifying the WB.   I have learned to accept it - I guess the alternative is to splurge out more and get the Lee or the Sing-ray ones.

Guido
 
Posted 3 months ago

Guido Brandt wrote
I have read somewhere on the net that it has to due that the different wavelenghts of light are filtered differently with the ND/grads filters. I have found in the past that the problem is intermittently, which makes me believe it has a lot to do also with the angle of light.
Hi Guido
I had thought that it was imtermittant as well but then thought I was imagining it. It really is annoying and on many occasions I don't seem to be able to remove it by changing the WB.
 
Posted 3 months ago
As you use a CMOS sensor on your D300 you may find this useful 
Flickr Group...'Hitech Filters'
The thread was started 3 March 2010
Caledonia Alan  http://l.yimg.com/g/images/badge_pro.gif.v2" width="20" height="12" alt="Pro User" class="ProIcon" style="border-top-style: none; border-right-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-image: initial; vertical-align: bottom; border-width: initial; border-color: initial; ">  says:Formatt who make Hitech say on their website..
NDs are made in different grades according to the level of light reduction. The standard grades are 0.1, 0.2, 0.3, 0.6, 0.9 and 1.2. Higher density ND's are also available to buy online in densities 1.5, 1.8, 2.1, 2.4 and 3.0.

Please note that these filters may not be suitable for cameras with a CMOS sensor. If you are unsure, please contact us for more information.

I contacted them about this as instructed and was told the 1.2 - 3.0 filters should work ok on SLR cameras but no guarantee they will work on DSLR's. This was the exact replyThe filter does not work with cameras with a CMOS sensor, but should be OK with SLR cameras. This is because cameras with the CMOS chip have an increased sensitivity to Infra Red light. When using darker ND filters and longer exposure times, more IR light passes through the lens. The CMOS chip cannot cope with it, so it leaks through to the final picture, turning it red

However, I have investigated this further and it has to do with each individual camera's ability to block infra red light, some cameras have better in-built IR blocking filters than others so with some there may be a colour cast with the ND filter used and with other cameras there may not be.

I have a 10 stop B+W filter and on my camera it didn't produce a colour cast but on someone else's it did but it seems to depend on how dark it is and how long the exposure is because there have been times when it has produced a cast, usually late evening. It always seems to be okay if there is sunlight 

...and more interesting discussion follows
 
Posted 3 months ago

Charlie Packard wrote
I have a 10 stop B+W filter and on my camera it didn't produce a colour cast but on someone else's it did but it seems to depend on how dark it is and how long the exposure is because there have been times when it has produced a cast, usually late evening. It always seems to be okay if there is sunlight
I also have a 10stop and I don't recall having a problem with that, only the 0.6 and 0.9 stacked (not individually). It may well be something to do with exposure time as well as a specific combination. I'll have to try and make a note of just when it is happening.
 
Posted 3 months ago
Tim Wilcock wrote

Charlie Packard wrote
I have a 10 stop B+W filter and on my camera it didn't produce a colour cast but on someone else's it did but it seems to depend on how dark it is and how long the exposure is because there have been times when it has produced a cast, usually late evening. It always seems to be okay if there is sunlight
I also have a 10stop and I don't recall having a problem with that, only the 0.6 and 0.9 stacked (not individually). It may well be something to do with exposure time as well as a specific combination. I'll have to try and make a note of just when it is happening.
Sorry Tim, that was Caledonia Alan's post...not my comment :)  The cut and paste of Flickr's page to 1x was very poor!!

I use Lee and don't have problems with stacking ND Grads
 
Posted 3 months ago
Charlie Packard wrote
When using darker ND filters and longer exposure times, more IR light passes through the lens.
...*relatively* more IR light passes through the lens.
 
Posted 3 months ago
Tim, I think Charlie has covered it well.

It is IR pollution, you will ususally only see it in the top half of your image as a magenta/red cast in clouds and sky, as it is a pollutant it is hard to rectify, WB doesn't help much and I never had the patience in PS to try and solve it. I got rid of the filters that created it, a Hitech 10 stop and Cokin P series.

However, I still use Hitech 0.6, 0.6 and 0.9 ND grads along side my Lee ones. I use my Lee 0.6 and 0.9 ones first then may use only one of the Hitechs and this works fine.

If I stack two Hitechs then I can become susceptible to the problem but two Lee ones are fine. You pay the money for Lee but you are buying quality.

JP



 
Posted 3 months ago

John Parminter wrote
You pay the money for Lee but you are buying quality.
More flaming expense! I upgraded to Hitech from Cokin, as I thought they were equivalent quality and available rather than back order. Always paying for something.........
 
Rui Pires  Curator
Posted 3 months ago
Try Lee filters, colourcast disapear :)
 
Posted 3 months ago

Tim Wilcock wrote

John Parminter wrote
You pay the money for Lee but you are buying quality.
More flaming expense! I upgraded to Hitech from Cokin, as I thought they were equivalent quality and available rather than back order. Always paying for something.........
Take up fishing Tim, it is less expensive, time consuming and frustrating....
 
Posted 3 months ago

John Parminter wrote
Take up fishing Tim, it is less expensive, time consuming and frustrating....
Yes but boring and I wouldn't get to rise really early from my bed in the freezing cold and dark, drive 40miles to my chosen location, hike a mile or two, stumbling over rocks, falling into burns or risking falling over cliff edges THEN to find that the sunrise never happened, the sky was crap or boring or both and what rubbish I did snap had a terrible red colour cast.

Then again maybe fishing isn't such a bad idea......
 
Posted 3 months ago
I found an interesting explanation for the magenta colour cast with ND filters at the following URL
http://www.bulbexposures.com/home/2011/10/11/nd-filter-color-cast.html

This seems to be a viable explanation to me anyway.
 
Posted 3 months ago

Keith Doucet wrote
I found an interesting explanation for the magenta colour cast with ND filters at the following URL
Thanks Keith. May be worth trying one of these. Just a few days ago I used my 10stop in good daylight and ended up with magenta images which I'm finding very hard to correct in PS. I was on the point of deciding not to use it again but this might be an option.
 
Posted 3 months ago
No problem Tim. Glad I could pass that information along.
You may want to consider doing B+W with your Magenta Cast images if they lend to that style (have the tonal range).
 
 
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