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50432Re: zebra sky help

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  • web@drmattnolan.org
    Jul 3, 2011
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      Thanks Jürgen. I checked my D300, and WB is set to "d-0", though with raw shooting I'm not sure that this setting should influence anything but the preview jpg embedded into it (but 'should' often enough doesnt matter with programming...).

      My workflow is simply to download the raw images, open them in Adobe Bridge, select them and open in Camera Raw, and then tweak them all identically using the Synchronize command until the brightest and darkest images are the best compromise. Then I write them out as 16 bit tiffs and ingest into PTgui.

      One thought I had is wondering how PTgui does exposure blending? That is, if an image is completely blue sky and the adjacent one has a bit of white cloud or dark mountain in it, might PTgui adjust the overall exposure (lighter with a bit of cloud or darker with a bit of mountain) such that the blues no longer match brightness? I guess a test might be to take a single image, duplicate it, arrange it in a row in PTgui, and add black or white corner to some of them and see if the zebra pattern emerges.


      --- In PanoToolsNG@yahoogroups.com, "jrgen_schrader" <panorama@...> wrote:
      > Uh, that looks harsh, not like vignetting.
      > Just to be sure: Could you please check that also WB in the RAWs is set to anything else but "Auto". To track down a possible error in the workflow you might want to give a detailed description from RAW developing through stitching. At which aperture were the images taken?
      > Best
      > Jürgen
      > --- In PanoToolsNG@yahoogroups.com, web@ wrote:
      > >
      > > I've noticed on several of my gigapixel panoramas that there is a vertical banding problem, something like zebra stripes. It seems like every other image or so is brighter than the other, so that from left-to-right there is not a seamless sky but rather alternating light and dark. It is subtle, but clear, especially when you zoom out. It shows up in snow fields too.
      > >
      > > Here is an example (not sure whether this works on a Mac):
      > > http://www.drmattnolan.org/photography/2011/ahab_gigatest/ahabridge_20k.htm
      > >
      > > This is a 20k wide version of a 120k pixel wide original; the zebra pattern is present in the full size original in Photoshop, so its not a resizing or HDview problem. Workflow was 16 bit throughout, from NEF to sRGB tiffs to PSB, then output. The images were shot with a D300 in manual mode with nothing left to chance (that I know of... but definitely not shutter speed, aperture or iso... not sure what else is left when shooting raw) and processed identically in ACR to tiff. Putting the tiffs side by side I dont notice an exposure difference, but I havent tested it well either. In PTgui, I tried with and without the exposure optimization tool, with not much difference. I guess I'm thinking I'm either missing some setting in PTgui or some setting on the camera, but before I spend much time with it I was hoping someone might already be familiar with this issue and could let me know the cause?
      > >
      > > Thanks,
      > > Matt
      > >
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