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Taken by
The Gigapanographer Currently Known as "Kilgore661" The Gigapanographer Currently Known as "Kilgore661"
Explore score
119
Size
0.48 Gigapixels
Views
818
Date added
May 21, 2012
Date taken
 
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Description

Work in progress.

Does anyone know how to cut the sky out of an image? I have been trying all sorts of different techniques but they all have the same problem viz there is no substitute for the human eye.


Gigapan Comments (8)

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  1. The Gigapanographer Currently Known as "Kilgore661"

    The Gigapanographer Currently Known as "Kilgore661" (May 23, 2012, 07:46AM )

    Thanks for your help and ideas guys. I have put what you have been saying together and come up with a very simple (and obvious with 20-20 hindsight :-) technique. Stack dark layer over normal layer. Use the lasso tool to drag a line along the horizon (watching out for things like white tents sticking into the sky). Do this to an accuracy of N pixels where N doesn't need to be small. Now modify the selction by feathering it by N. Now make a mask for the dark version and flatten. You can see my result for N = 20 here: gigapan.com/gigapans/105958

  2. Planet Vision

    Planet Vision (May 22, 2012, 11:09PM )

    Tom's suggestion sounds like a winner. I'm thinking that it would also require some type of gradient on the mask so that the sky at the transition with the land is lighter but darkens gradually above. I believe that is possible to do. Great mini tutorial here.

  3. Tom Nelson

    Tom Nelson (May 22, 2012, 07:35PM )

    Make a normal version (sky burned out) and a darker version (good sky). In Photoshop, drag the dark version onto the light version, holding the <shift> key to make it register perfectly. Hide the dark layer, then use the Magic Wand to select just the sky. Select>Modify>Expand 1-2 pixels. Now select the dark layer and make a layer mask.The little circle-in-rectangle icon in the Layers palette. The sky shows only where the selection is. Now change the blend mode of the sky layer to Darken. Tree branches, etc, on the horizon reappear. You may need to lower the opacity of the sky layer slightly because lighter leaves and branches will be partially burned-out by the bright sky.QED.

  4. Planet Vision

    Planet Vision (May 22, 2012, 10:08AM )

    What if you gave Enblend two images to work with and blend the seam between the sky and land. You'd just have to create the alpha channel mask for it to work with and that you could paint in rather easily in PS for the one image and then invert it for the other. Saving each image in turn. It has been a while since I've used Enblend from a command line but it has some options as to the distance it is blending (I believe anyway). If you're quick in PS that might work for you. I always liked the blending from Enblend. I did find some ghosts, at least three. Two are an individual moving and the third looks like it came from the tone map. The pano is rather nice. There are hints of tone mapping when you look at it close up - subtle is good. If you have it in PS, crop the sky a bit lower to remove the seam locations ... it will be near perfect in my opinion.

  5. The Gigapanographer Currently Known as "Kilgore661"

    The Gigapanographer Currently Known as "Kilgore661" (May 22, 2012, 04:01AM )

    @Planet Vision Yes, I wanted to replace the sky. In the basic +0EV shot the sky is almost completely white because it was a grey day. The sky in this image is made from the same photos but tone-mapped to bring out the structure in the clouds. I agree that the sky looks fine when you are zoomed out, but if you zoom in you'll see that the line between the dark sky and the bright land is very crude. I imagine that if I spent a lot of time using photoshop and masks then I could improve the boundary, but what I am really looking for is a technique that is accurate and *fast*.

  6. The Gigapanographer Currently Known as "Kilgore661"

    The Gigapanographer Currently Known as "Kilgore661" (May 22, 2012, 03:52AM )

    @David All I did was to shoot the scene twice and then stitch using Autop*no using ghost removal. Plus I got lucky in that there was nobody in the wrong position in any frame in either pass.

  7. Planet Vision

    Planet Vision (May 21, 2012, 10:54PM )

    I think the sky is fine give the attire of the participants. Can you go back and shoot a nice day and then mask it in cutting below the treeline where the eye can be deceived somewhat? You might have to do each frame individually, warping as you go unless you could mask the individual images before stitching. You might be able to make the latter happen in PTGui. Actually, I should ask ... is that your goal - to replace the sky?

  8. David Engle

    David Engle (May 21, 2012, 08:07PM )

    Have you been keeping secrets from me? Did you buy a new camera and instantaneous GigaPan maker? How did you accomplish taking a good sized GigaPan with people and dogs in it and obviously moving around, yet there are no stitching errors. How did you do this???

The GigaPan EPIC Series, Purchase an GigaPan EPIC model and receive GigaPan Stitch complimentary

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