NX2:Gen - Fixing Poor Use of CP Filter

Discussion in 'Nikon Capture and View NX' started by NewBert, Sep 20, 2008.

  1. I attended the Adirondack Balloon Festival yesterday, and used my Sigma 10-20 and Circular Polarizer for the first time in several months. While many of the images came out fine, many others came out like this:

    103401293.

    As you can see, the sky is very uneven - a consequence of using the CP filter improperly, I think. This unwanted effect happened with every shot taken with the sun off to the right. Time of day was perhaps 40 minutes before sunset.

    What would be the best way to correct the uneven sky in NX2? Note: While the original image is NEF, this image is a JPG just for posting here. It is straight out of the camera with no post-processing at all.

    Any help would be appreciated.
     
  2. I would suggest dropping a Color Control Point in the upper right corner of the image.

    Once you've selected the area of the sky that is the darkest blue, I would then boost the brightness and reduce the saturation of that area. That tends to bring the darkest portion of the sky more in line with the remainder of the sky.

    I had to do this on several images that were over-polarized when I was digitalizing my Kodachrome slides a while back!

    Glenn
     
  3. Bert, I second Glenn's recommendation. However, before you do the local adjustment with the color control point, I suggest that you globally adjust the image using either the LCH editor or the EV compensation to increase the overall exposure about 1/2 to two-thirds of a stop.
     
  4. Bill,

    While the revised image is certainly brighter and less saturated, it appears to be more of a global adjustment (rather than a local one).

    I think the power of NX2's Color Control Points (or Control Selection Points) is the ability to make the same adjustments locally--and to do it very quickly.

    Glenn
     
  5. Thanks, guys. I'll give the color control point a go.

    Mike - The image came straight from the camera so I realize that some global adjustments will be necessary straightaway (including ev compensation and probably white balance).

    Thanks again!
     
  6. Bert, I just got another idea. Due to the position of the deep blue part of the sky, especially in the top right corner, you might want to use the Linear Gradient Tool to control the effect of the Color Control Point. Doing that might help you blend the right side of the image with the left side.
     
  7. I don't understand why this would not occur with any circular polarizer. Can you explain?

    As a side note, I use a B+W Kaesemann MRC circular polarizer, and I can produce this effect. I don't think the brand of polarizer matters here, but perhaps I am wrong.
     
  8. Terri French

    Terri French

    May 5, 2005
    Idaho
    I've given up using a CP when using the wide end of the 10-20. The view is so wide that the effect of the polarizer just can't work evenly across the entire range. It was one of the first lessons I learned from and experienced landscape photographer when I got the Sigma 10-20.
     
  9. I've had some success when shooting directly away from the sun. But overall, I avoid it as well.

    I've always wondered how the Singh Ray Vari-ND filter handles this. It's 2 stacked polarizers, so I would think that there might be some unevenness. However, I've never come across mention of this sort of problem.
     
  10. Having owned a few circular polarizers in the past, I don't think that the brand of polarizer would make much of a difference in handling that issue. I stopped using my polarizer on very wide angle shots.

    Glenn
     
  11. I agree that it depends on the where the sun is. The effect shown in the image that I posted occured with shooting at right angles to the sun (ie - side-lighting). In my images that were shot with the sun to my back, the effect was either gone or not nearly as bad. However, shooting with the sun at my back negates much of the benefits of using the CP in the first place, doesn't it?
     
  12. Well, it depends on why you are using the polarizer in the first place.

    In general, I use polarizers to reduce the effects of glare from water and snow. This can be relevant regardless of the direction that I am shooting (relative to the sun, that is).

    I also sometimes use my polarizer when my 5 stop ND filter is not enough. Most high quality polarizers will block another 1 1/3 stops of light (and most low quality polarizers will block more!). Of course, I have to keep the uneven-blue-skies thing in mind when I do this.
     
  13. I have very little experience using a circular polarizer at the wide end of a wide-angle lens, but coincidentally I reprocessed an image involving a similar situation immediately before reading this thread tonight. It was shot at 12mm on a DX format. I was curious to see how the Picture Control Landscape would look with it because that was not available when I first processed the image. It unattractively exagerrated the difference between the light and dark area of the polarized sky. When I used the Picture Control Standard, the sky looked great, at least to my eye, with no need for using a control point.

    I'm beat right now but I'll post the image tomorrow using a few different Picture Control settings so you can see the impact on the sky. I was really surprised and you might be too.

    For the record, my polarizer is supposedly a high-end product, though not ridiculously high-end. It's the ProMaster polarizer and it's their best quality. The 72mm size cost $160 in a store (not an Internet sale).
     
    Last edited by a moderator: Sep 24, 2008
  14. Mostly interested by this thread !

    It looks like there are quite a few "tricks" that one can acheive very easely with NX 2, but which would take ages using Photoshop :eek:  !!!

    Bookmarked it !

    :smile:
    J-P.
     
  15. While I don't disagree with this statement, the fact that you are seeing a homogeneous sky at 17mm doesn't necessarily imply that Bert's shot at 10mm would have benefited from a "better brand".

    The following picture was shot at 11mm using a B+W Kaesemann MRC circular polarizer.

    _DSC2023.

    The sun is off to the right.

    As a side note, if you're itching to do some skiing, the Old Goat Glacier had over a foot of powder two weekends ago. Just make sure to avoid the crevasses. :biggrin:
     
  16. Either the sun was coming from the left side or you flipped the image. :biggrin:

    I actually like the variation in the sky to a certain extent. Whether I am wearing polarized sunglasses or no sunglasses, if I look at the sky in later afternoon or early morning with the sun to my right or left, the sky is not consistently one colour throughout. Though I don't try to make my pictures an accurate documentation of reality, it is pleasing to know that at least a limited amount of variation in the sky is both aesthetically pleasing and reasonably accurate.
     
  17. Was that on a DX format or a full-frame format? Does the format matter? I don't think the format matters but maybe someone knows for sure.
     
  18. I think what matters is the angle of view. In my case, it was DX format, which translates to 93.8 degrees of horizontal field of view.

    At 10mm on DX (Bert's shot), that's 99.3 degrees.

    At 17mm on DX (Tom's shot), that's 69.4 degrees.

    Note that I'm making assumptions here (Bert shot at 10mm, Tom shot at 17mm, different Nikon APS-C cameras have slightly different crop factors, etc ...).
     
  19. Ha ha. It took me a second to figure out what you meant. Clever.
     
  20. Okay, fair enough.

    I heard 2006/2007 was a very bad winter in the Alps. Not sure about 2007/2008. But I hope 2008/2009 proves to be a good one!

    Looks like it's going to be a good one in the Rockies this year. Unfortunately, we've already had 2 avalanche fatalities. :frown:
     
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