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Cokin filters colour cast

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petecorrigan
 
Posts: 4

Cokin filters colour cast

Post Wed Sep 17, 2008 6:14 pm


I have purchased 2 Cokin P filters ND8 and ND8 Grad, fine on their own but used together a very strong pink tint is visible in the viewfinder, or just with the two filter held together against the light, have emailed the UK importers Intro 2020.co.uk but failed to get a response. :(

Has anyone had the same experience ? I thought ND was neutral and not supposed to give colour casts

PeteC

prinothcat
 
Posts: 662

Re: Cokin filters colour cast

Post Thu Sep 18, 2008 12:05 am


petecorrigan wrote:I have purchased 2 Cokin P filters ND8 and ND8 Grad, fine on their own but used together a very strong pink tint is visible in the viewfinder, or just with the two filter held together against the light, have emailed the UK importers Intro 2020.co.uk but failed to get a response. :(

Has anyone had the same experience ? I thought ND was neutral and not supposed to give colour casts

PeteC

Yes there is a strange reddish tint when two ND8's are overlapped. In my case it's almost purple. I don't see it under indoor light but it's there under sunlight.

petecorrigan
 
Posts: 4

Re: Cokin filters colour cast

Post Thu Sep 18, 2008 6:29 pm


Thanks for the reply, I will go with pinky purple, to much to use the filter. I wanted to use them together to really slow running water or wave shots, with that colour cast there totally useless together

PeteC

prinothcat
 
Posts: 662

Re: Cokin filters colour cast

Post Fri Sep 19, 2008 11:27 pm


petecorrigan wrote:Thanks for the reply, I will go with pinky purple, to much to use the filter. I wanted to use them together to really slow running water or wave shots, with that colour cast there totally useless together

PeteC

You might try a round screw in ND8 under the grad, or you're headed to high quality squares like B&W. If you need to use it on more than one lens diameter, purchase the biggest diameter you need and a step up ring to fit it to the smaller diameter lens. For example I buy rounds in 77mm because that's what my big lenses are. I then use a 67 to 77 step up ring so they fit my smaller lenses. Seems to me that I've rarely needed more than an ND 8 and iso 100 to slow water down. All depends on lighting though doesn't it. I'm intrigued by the color when the two are stacked.

petecorrigan
 
Posts: 4

Re: Cokin filters colour cast

Post Tue Sep 23, 2008 6:42 pm


Thanks for the info, I was using them for a slow the sea effect in good light, and found ND8 not enough, I already had a ND grad so tried the two and found this pink/purple shading, I have a 67mm polarizer and have used that with the ND8 with no problems, I have also heard that using two circular polarizers and rotating one against the other will cut the light down up to an ND9 in strength, but have not tried this yet, but as you say the best is to purchase better quality grads, you pays yer money :((

Pete

prinothcat
 
Posts: 662

Re: Cokin filters colour cast

Post Wed Sep 24, 2008 1:03 am


I usually shoot in subdued light so that's probably why I don't often need more than an ND8. I wonder about stacking two polarizers. What do you suspect they might do to highlights? Intuitively I wonder if this might cut too much dynamic range out of the exposure. I don't have the filters to try it, so I'd be interested to see what happens. As was mentioned in another posting, you might need to watch for vignetting on some wides and super wides when you stack filters, especially CP's since they tend to be have thicker rings.

petecorrigan
 
Posts: 4

Re: Cokin filters colour cast

Post Wed Sep 24, 2008 5:35 pm


I read about it on some forum, but like you have only one polarizer, Apparently some space capsules used 2 polarizimg filters on the windows to darken the sunlight, have no way of knowing if this is truthful, I find a bit of vignetting between 17mm and about 22mm on both my circular filters, if the picture is good I just trim to suit in post processing, thought we might have had a few others commenting, must be a common problem or perhaps not many stack filters ?


Pete

prinothcat
 
Posts: 662

Re: Cokin filters colour cast

Post Thu Sep 25, 2008 12:01 am


yep a bit of vignetting at 17mm would be expected. There are CP's made with thin mount rings. By whom I can't say right now. I have to watch my 16mm with Cokin holders for sure. It's one of the reasons I try to buy 77mm round filters and use step up rings to fit them to my 67mm diameter lenses. It helps push that ring further outward from the edge of the frame. I'm betting most avoid stacking filters for the reasons we have discussed. I also suspect that many folks here have either not seen the color cast or are using higher quality glass ND's and grads. I'm using the Cokin's to figure out which ones I will actually use, then will buy B+W's as I destroy the Cokins.


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