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Best Sky Blending techniques??


RossCKelly

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Hi, I'm doing some conceptual photographs that involve stitched panoramas on cs6 starting from the ground and going upwards so that the sky goes from light blue to dark blue over 4 or 5 photographs. I really want to get a perfectly smooth transition but when i align layers and then auto blend them I always seem to get a series of dark horizontal patches like stripes where the photographs overlap... Does anyone have any experience with this or could anyone suggest a remedy? Alternatively , is there a better way of blending skies manually to ensure a smooth gradient?
It would be a great help.
Thans,
R
 

iDad

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If it were me and I had all the photos stitched together I would create a layer on top of sky select the blue that I wanted to use put it on that top layer where it needs to be and use of blending modes. But not saying the image and the degree of change in color really a guessing game, I suppose you could always feather the skies area
 

ibclare

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If there is any overlapping there will be a problem. But whatever the case, I prefer to use the stamp tool like an oil brush. You have to use varying opacities, and "paint" back and forth. You could, depending on the complexity of the image lay another sky over it, mask it and blend the edges in, adjust thecolor if needed. You could also clone an entire section of the sky and move it over to the striped area. Then apply a mask and blend out the edges. It's a matter of experimenting to see what works best with the sky sample you have.
 

Paul

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Make sure it is a clear blue sky day could be your answer.
 

iDad

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You should post the sky so we can see. Take a screenshot of just the sky if your not interested in posting whole image.
 

Tom Mann

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@OP -

1) First, and most importantly, I presume you know that to minimize banding, your camera absolutely MUST be on manual exposure mode? In addition, manual focus mode is definitely preferable to auto-focus.

2) Second, I presume you realize that all camera / lens combinations, even top-of-the-line, $2000 Zeiss manual focus prime lenses, exhibit some degree of vignetting. In other words, every image they produce is slightly darker than it should be around the periphery of the image. On many low-end DSLRs with the kit zoom lens, this effect can easily exceed 1 or 1.5 stops of darkening, especially if used wide open. So, if you don't take care to minimize this, you (or your stitching algorithm) will have a vastly more difficult task to perform.

The easiest (and best) way to remove this problem is to use with a camera / lens / f-stop combination that exhibits only a small amount of this behavior. Then, before stitching, process each image through either ACR or LR and use the "Lens Correction" facility to reduce the amount of vignetting by a large factor. If your lens / camera combination is in their database, this step is completely automatic - it's just a single button-push.

3) If, in spite of taking all of the above precautions, I discover that there still is banding after using good stitching software, I find that a few applications of patch tool to be far and away the best method to remove it. The content aware fill tool also seems to work quite well, but since it made its relatively recent appearance in PS, I haven't done very many vertically stitched images, so I have less familiarity with it for this application. IMHO, for horizontal sky banding, either of the above runs rings around the clone/stamp or smudge tools.

As with all digital imaging problems, it's vastly better to minimize the source of the problem (ie, my suggestions #1 and #2, above) rather than trying to put a band-aid over the problem (ie, #3) in post processing.


HTH,

Tom M


PS - I also presume you have thought about holding the camera in portrait orientation so that you don't have to stitch together as many images to cover the sky?
 
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Tom Mann

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BTW, here's an example of using the patch tool to repair banding in the sky.

First, I made a fake gradient to simulate a real gradient that might be present in the sky.
 

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  • Untitled-1-01_original_gradient.jpg
    Untitled-1-01_original_gradient.jpg
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Tom Mann

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Next, I simulated banding by running the previous image through the image / posterize filter. Hopefully, this level of banding is vastly more severe than what you are trying to fix in the output of your stitching program.
 

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  • Untitled-1-02_posterized_original_gradient.jpg
    Untitled-1-02_posterized_original_gradient.jpg
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Tom Mann

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Finally, I smoothed out the hard steps using the patch tool.

To do this, I first made a hard-edged rectangular selection centered on the first horizontal edge, and with a height about equal to one step. I then switched to the patch tool (normal, source, mode) and dragged the selection upwards by a distance equal to about one full step. This nicely smoothed the 1st transition.

Working my way downward, I then repeated the above for each of the remaining horizontal edges. The result, attached below, is very nice -- surprisingly close to the original.

I think it would take a lot more effort to get the same quality of smoothing using the clone or smudge tool.

Tom M

PS - I wouldn't consider simply running a blur over the sky because it would introduce a large change in digital noise, would smooth out any clouds that were present, etc.
 

Attachments

  • Untitled-1-03_bands_fm_posterization_fixed_using_patch_tool_at_each_transition.jpg
    Untitled-1-03_bands_fm_posterization_fixed_using_patch_tool_at_each_transition.jpg
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iDad

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Those are awesome Tom but it could be a nightmare ifa delicate selection process needed trees etc, what layer mode technique would help with overlay of that, I know it's hard to say without seeing image
 

RossCKelly

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Sorry, I should indeed have added this image.Untitled-27.jpgIt may be hard to make out the darker areas but the print size is 9" x 36" and you can definitely make out there
Shot on Fuji X-Pro 1 with 35mm prime. Not on manual but with exposure locked moving upwards to keep constant.
Theres about 4/5 images in the sky.
Very interesting point about the vignetting... ill definitely check that out as well as the other blending options.
Is it better to have more overlap of images when auto blending in cs6 or is that just for auto align?
Thanks so much for all the responses
r
Thanks so much for all the responses.
 

iDad

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I assumed it would be horizontal not vertical like that . I'm on an iPad and from what I see there is not a problem, but its at 72dpi and tiny image from what I see
 
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iDad

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beforeView attachment 31961 afterView attachment 31962I had to get on the big computer for this one I took a shot at it and I took a rough selection of the sky on the horizon feather it 50 pixels copied it pasted it as a upper layer put it in screen mode and it lightened up really nice, looks good I think I see the dark area you talk about
 
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RossCKelly

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Wow that does seem better! Thanks.
Ideally I was teying to keep the darker sky, particularly at tthe top. I'm trying to get a sense
of the atmosphere thinning as you go upwards. Can that be achieved with this technique ?
I thought of putting a gradient layer underneath and change the opacity of the sky.
 

iDad

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Not on computer again but I would think levels adjustment may get it there or even another layer mode play around with those then I would try brightness contrast on the upper layer The gradient may work as Tom pointed out I believe
 

IamSam

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Ross said:
Alternatively , is there a better way of blending skies manually to ensure a smooth gradient?

Here's another way to skin the cat. Not always applicable, but works well.

Photo 1
Panorama_01.png

Photo 2
Panorama_02.png

Combined
Panorama_03.png

Masked (this is a PNG with transparent BG).
Panorama_04.png

Created my own gradient by using the color picker to choose colors from original images.
Applied gradient to a new BG layer.
Panorama_05.png

You could also add clouds with brushes, soften the edges and so on.........
 
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Tom Mann

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Even if I dramatically enhance the local contrast to intentionally exaggerate such flaws, I really don't see a stitching problem. However, I *do* see a moderately strong banding problem. (see attached). The solutions to the two problems are quite different.

If the bands in my version are not what is bothering you, could you pls post a version of this image where you have made the stitching problem easier to see.

Thanks,

Tom M
 

Attachments

  • Untitled-27-tjm01_acr-ps01a_enh_local_contrast-01.jpg
    Untitled-27-tjm01_acr-ps01a_enh_local_contrast-01.jpg
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