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Author Topic: Anyone use PTGui Pro?  (Read 16373 times)
bill t.
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« Reply #60 on: April 03, 2010, 06:00:05 PM »
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Absolutely, John is The Man when it comes to explaining panos.  Highest recommendation.

Have shot many panos with why automatic Fuji F31 point & shoot.  The basic problem is that while you would hope the autoexposures would gradually trend this way or that from frame to frame, in fact whatever heuristics are involved tend to generate big jumps from frame to frame.  The exposure stack I mentioned in post #49 of this thread is about the only way to deal with that, when you are dealing with the usual .jpg's from the P&S's or even fairly thorough raw conversions on autoexposed originals.

In practice even with the DSLR's I sometimes fudge the frame to frame exposure time slightly when shooting in manual mode as the as the scene brightness changes with sun angle and overall contrast.

Here's a personal pano I shot in autoexposure with the F31.  It shows the basic kind of sky blending problems you get from autoexposure, and a somewhat paint- brushed solution.  That camera sure has a lot of depth of field!
[attachment=21258:Tondreau_Sky_Blend.jpg]

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Michael Bailey
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« Reply #61 on: April 03, 2010, 07:23:30 PM »
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Hey, Bill T., don't go messing up my perfectly sound theory with grubby reality! How can I hope to become an internet blowhard if you mess me up with empirical evidence?

Now let me tell you about how the Nikon Corporation is in league with the Trilateral Commission to create an international pixel tax...

MB
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bill t.
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« Reply #62 on: April 03, 2010, 10:05:18 PM »
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Quote from: Michael Bailey
Hey, Bill T., don't go messing up my perfectly sound theory with grubby reality!
Dont feel bad!

You had some good points there.  While in theory pano purists like to hold a constant exposure from frame to frame, that can lead to badly exposed panels on panos where some parts of the scene are a lot brighter or darker than the rest.  The argument for autoexposure is that while you may get a wild and crazy bunch of jumping-around exposures, you at least will not get really awful exposures.  You can equalize wild exposures in the layer stack as long you don't have too much clipping, but you can't satisfactorily rescue badly clipped areas except for sky reconstructions.

The best procedure on exposure-challenged panos is usually to shoot HDR, which is my choice in those cases.  But if you don't like HDR, then please feel free to either nudge the exposure around from panel to panel by keeping an eye on the histograms at shooting time, or just shoot autoexposure if that's all the camera allows.
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Michael Bailey
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« Reply #63 on: April 04, 2010, 01:12:03 AM »
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Yes, of course you're right about checking histograms and getting exposure right at the source. To avoid the dive into HDR, here's how I've been approaching exposure:

shoot raw, as all people of virtue and kindness will agree

bracket (why oh why do the Nikon D-300 and D-700 only bracket in 1 stop increments while the D-90 will allow variation of 1.5 stop and more?)
---and, yes, if part of the scene is definitely brighter or darker, cheat the base exposure

in processing, use ACR (or other) to fudge the exposures from frame to frame a little more
---they don't have to all be perfect exposure matches--the stitching software may surprise you with how well it blends
---process the files so their values fall more to the mid range, even if it makes the pictures look a bit flat
--- ---you don't want to throw away highlight and shadow information yet if you don't have to
---of course, don't feel obligated to choose the same bracket from each set
---also, alter individual color balance settings if the color varies across the scene
---CS-4 also has the nice adjustment brush feature to help with smaller local corrections

work in 16 bit color
---16 bit makes my 13 D-90 files twice as big but PT Gui can still process them fairly quickly
---that last inevitable bit of Photoshop tweaking will look smoother in 16 bit, as will the whole file when you apply the adjustment layer to goose the contrast back to normal


the Shadow-Highlight tool is a great help, too
---duplicate the final Photoshop layer, run S-H on the duplicate, then use a layer mask to make it disappear in the places you don't want to see it

So, to control the tonal range of very wide scenery, here's a list of tools that I see so far:
  • shoot raw
  • vary base exposure from frame to frame, if necessary
  • bracket
  • refine individual exposures and color balance in raw processing
  • do some "dodging and burning" with the adjustment brush
  • rely on stitching software's ability to blend edges of differing brightness
  • 16 bit color for better manipulation of details and tonal range in finished pano
  • shadow-highlight

Is this a complete list?

MB
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