Correcting polorising filter distortions?

Norfolkbloke

Norfolkbloke

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I'm sure there is a proper term for it but I've recently been experimenting with a circular polorising filter on my Tokina 11-16 f2.8. As much as I like the change in colour tones, when I used it to full effect I noticed most if not all of the pics I had taken of clear blue skies had an unsightly blue blob to one corner of the frame. I now know the reason and cause of this but has anyone actually tried correcting for it using the selections tool/saturation/brightness etc ..or is it even possible?

Unfortunately I no longer have the image files to upload as they have long been deleted so can't post up to bare all!

NB
 
No... with such a wide lens, he's referring to the angle of view being so wide, only part of the sky is actually polarised. It can be corrected, but not easily. I know of no automated process.

Personally I wouldn't, and don't use a polariser with a lens that wide on shots with loads of sky involved: More trouble than it's worth.
 
It's not lens flare he's talking about, a blue blob doesn't sound like only part of the skys coloured.
 
I'm not talking about lens flare. With a 11mm lens your field of view is very wide, and a polariser is only really effective on a blue sky at 90 degrees from the sun. Only part of the sky will ever be polarised with a lens like that.
 
Pookeyhead said:
No... with such a wide lens, he's referring to the angle of view being so wide, only part of the sky is actually polarised. It can be corrected, but not easily. I know of no automated process.

Personally I wouldn't, and don't use a polariser with a lens that wide on shots with loads of sky involved: More trouble than it's worth.
Click to expand...

Thanks for the replies, I did find a couple of vids on youtube warning of using a CP filter on an ultra wide angle lens..to be honest due to poor weather and lack of spare time shooting I only had a couple of days with the set up but discovered pretty quickly CP filters are best left to more standard/tele zooms. I also tried combining it with a 0.9 ND Grad filter and the results were even more pronounced as you can imagine!

There was only one shot I was keen on rescuing but several attempts in Elements failed to produce the desired result...I think also I lost a bit of sharpness as a result of the filter so will have to go back to the drawing board on that particular shot! I'm now using a 35mm f1.8 on my D7000 so looking forward to seeing how that set up copes with a CP filter, just as soon as we get some sunshine that is!!

NB
 
The 35 will be fine, as that's a standard lens for a D7000.
 
This is inline with my experience, in that they spoil as many pictures as they improve (a bit).
I never use them now, one less thing to worry about.
 
Pookeyhead said:
I'm not talking about lens flare. With a 11mm lens your field of view is very wide, and a polariser is only really effective on a blue sky at 90 degrees from the sun. Only part of the sky will ever be polarised with a lens like that.
Click to expand...

I know, but my skies don't come out as a blob even with a pola filter, you might get part of the sky coloured but a blob didn't sound right.
 
Perhaps it's his wording... it's the only thing I can image it could be though.
 
Depending on the position of the lens and the sun, it could be vignetting. I've had that happen with a polarising filter, noticeably in one corner but not so noticeable in the others.
 
How can the position of the lens in relation to the sun affect whether it vignettes or not? :thinking: If the filter vignetting, it will do it regardless of where the sun is.... all the time, everywhere.
 
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If you rotate the filter so that the sky appears at its darkest, at a particular angle relative to the sun, the vignetting will show up quite a bit on a cheap lens, sometimes to the point that the dark corner might be referred to as a blob. It's not that the vignetting depends on the position of the lens - it's the position of the lens relative to the sun that decrees how dark the sky appears and thus how visible the vignetting is.

Perhaps I could have made that clearer.
 
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