x_tan wrote in post #14824269
CPL Question: Far Too Dark In The Outer Area Is 'Natural Look' Or Not?I notice some of my shoots with CPL, the outer area is much into deep dark blue; which I don't feel natural:
Personally I rather have more even blue over the whole sky - so I should use Neutral Density or Graduated Neutral Density filter instead?
- The effect you see is totally natural and reliant on the way in which polarisation works.
- In fact, the total opposite of your title statement is the truth. The 'too dark' appearance is a direct consequence of how you set the CPL. Adjust only the CPL rotation on the lens (ie less polarisation dialled in, same focal length set, same composition) and the effect will reduce.
- No, using an ND 'filter' will change the entire scene and you would still have the imbalance between sky brightness value and foreground brightness value. Effectively, you would simply reduce the overall exposure.
- Yes, a graduated ND would work - after a fashion. As always, you then have to struggle with the straight demarcation between the ND portion and the clear portion of your 'filter'. There's always something which pops up and disrupts the effect.
Polarisation effect is always most apparent cross sun - with the sun either totally on your right side or totally on your left. As you turn either towards or away from the sun (up-sun or down-sun) the light becomes less polarised.
If you were to take a 180° (horizontal) angle of view image with the camera pointing directly
across the fall of sunlight, you would have a sky which was quite pale at each end of the image and quite dark in the centre. Swivel through 90° so the sun is in the centre of the image and you'd have a pale sky in the centre and dark at the edges of the image. Consequently, the wider the angle of view of the lens, the greater the difference visible across the sky. The same would also apply if the sun was just about to set and you pointed the camera straight upwards - darkest at the centre and palest left and right edges, but not at top and bottom edges.
Unfortunately, a polarising filter (linear or circular) is not a universal panacea. Very useful on occasion but with wide angle lenses you are virtually guaranteed to get the effect you show.
PS. This is all theoretical on my part. Living in the north of England, I have very little recent personal experience of sunshine. I vaguely remember it from 60 years ago when I was a little boy.
- I think our Government have banned it now! 
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