BANDING IN SKY

[Matthew Borkoski]

I'VE DONE SEVERAL PANORAMAS OVER THE LAST 3 MONTHS AND HAVE NOTICED A BANDING IN THE SKY AREA ON SEVERAL IMAGES. THE IMAGES STITCHED PERFECTLY BUT THERE IS UNEVENNESS IN THE SKY. ANYONE HAVE THIS PROBLEM?
ANY SOLUTIONS???

[PTGui Support]

Hi Matthew,

The unevenness seems to be caused by vignetting. PTGui can correct for
this, see https://www.ptgui.com/examples/vigntutorial.html

The banding might be caused by post processing 8 bit images. In PTGui
stitch to 16 bit TIFF to ensure the banding does not happen during
processing in PTGui. Banding may still occur though if you make strong
brightness or color adjustments though.

Kind regards,

New House Internet Services BV
Joost Nieuwenhuijse

-----------------------------------------------
PTGui - Photo Stitching Software

www.ptgui.com
For support see: http://www.ptgui.com/faq/
-----------------------------------------------

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[Erik Krause]

What exposure time did you use for your shots and how where they
oriented (portrait or landscape)?

The problem with short exposure times is uneven shutter movement. If the
opening and closing shutter move at different speed you get uneven
brightness across the image. For longer exposure times this is less of a
problem. PTGui can correct for vignetting but not for uneven exposure.

BTW.: Capital letters is considered shouting...

Please do not add attachments or images to your posts; instead upload

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Erik Krause
http://www.erik-krause.de

[Matthew Borkoski]

thanks

Matthew
Matthew Borkoski Photography Inc
14613 Pebblestone Drive
Silver Spring Md 20905
O 301-384-2930
C 301-346-5576
http://www.matthewbphoto.com/
www.linkedin.com/in/matthewborkoski/

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[Matthew Borkoski]

Checked exposures they were 1/60 also checked some other panos that were shot towards dusk at 4 seconds and still have the banding problem

Matthew
Matthew Borkoski Photography Inc
14613 Pebblestone Drive
Silver Spring Md 20905
O 301-384-2930
C 301-346-5576
http://www.matthewbphoto.com/
www.linkedin.com/in/matthewborkoski/


-----Original Message-----
From: pt...@googlegroups.com [mailto:pt...@googlegroups.com] On Behalf Of Erik Krause
Sent: Wednesday, April 19, 2017 5:58 PM
To: pt...@googlegroups.com
Subject: [PTGui] Re: BANDING IN SKY

[John Houghton]

On Wednesday, April 19, 2017 at 11:11:48 PM UTC+1, Matthew Borkoski wrote:

Checked exposures they were 1/60   also checked some other panos that were shot towards dusk at 4 seconds and still have the banding problem 

Matthew, In that case, we need to have a sample set of your images for investigation together with a copy of your project file (.pts).  Please upload them somewhere convenient and post a link here.  Use Dropbox, sendspace.com, or similar file sharing facility if necessary.

John

[tel...@gmail.com]

Matthew is not alone with this particular complaint. I make large panoramas to print, and banding in the sky is the bane of my existence. Most of my panoramas are cylindrical projections composed of two horizontal rows, each comprising 20 to 45 frames. The vast majority of problems I encounter is sky banding in the top row. I spend many hours (understated, if not accurate) micro-adjusting the exposure and color balance of the RAW images in an attempt to eliminate the banding. I use Bridge to dump the .CR2 files into the Photoshop Camera RAW Viewer. I watch the histogram as I move between frames--in particular, the blue line on the right side of the histogram. Large jumps in the histograms' blue lines invariably indicate the positions of the beginning or end of severe banding. Where the sky changes from light to dark, or vice versa, I strive for a smooth, even transition in the histograms. A small (or sometimes, not so small) adjustment to a frame's exposure can reduce the size of the blue line jump and improve the final sky rendering (small changes to the temperature are a secondary option), without adversely affecting PTGui's ability to blend the image successfully. This can be a painful, time consuming process, as I then convert the RAWs to .TIFs, rerender the panorama, and search for more unacceptable spots. Please understand, I undertake this effort only when necessary. My first rendering of a panorama is made from a set of .TIFs whose RAW frames have had minimal but usual and reasonable adjustments made to them.

Some things that may help, when help is needed:  reducing contrast within the camera itself, if available (contrast can be increased in the final image, after blending occurs); choosing a less saturated Camera Profile during RAW processing (Camera Neutral will usually produce less banding in the final image than Camera Landscape, and saturation can be increased in the final image, after blending occurs); avoiding the addition of too much Dehaze Filter (sometimes, some is desirable, but it can exacerbate banding; unfortunately, Adobe imposes size restrictions on the availability of the Dehaze Filter, and it may not be available to use on the final image); ignoring the Vignetting correction in Camera Raw and instead eliminating obvious dark corners with the Spot Removal Brush; masking the sky with the Adjustment Brush and then selectively changing the exposure of only the sky (to reduce large blue line jumps in the histograms of adjoining frames). I would also suggest scrubbing the rendered output at print size. The transition from light to dark will often be more gradual, and therefore more acceptable to the eye, than that viewed at thumbnail or fit to screen size.

The idea of uneven shutter motion had not occurred to me. I normally photograph at f/11 and somewhere between 1/320 and 1/800 of a second. I will slow it down and see what happens.

I have noticed that the shape of the layer masking in the final output of PTGui often employs straight vertical lines with doglegs (zigzags) at the top and bottom. I wonder whether a "drunken jigsaw puzzle" edge, more like the one used by Photoshop's Photomerge, might not be a serious improvement worth requesting. Photomerge seems to color-blend the edges, where pronounced banding occurs, more gracefully than does PTGui. Photomerge, however, has its own unique set of problems that makes PTGui my goto software.

Serious panoramography is neither for the faint-hearted nor for those in a hurry.

Best Regards

Rob

[PTGui Support]

Hi Rob,

Have you tried doing the vignetting correction in PTGui Pro?
See https://www.ptgui.com/examples/vigntutorial.html
and disable all corrections in Camera RAW to prevent it from interfering.

If PTGui can't fix it, could you make your project file available for
download, including a couple of the sky images?

Definitely don't do any dynamic color corrections such as dehaze,
shadow/highlights etc, on the individual source images. This will do
contents-dependent adjustments, so each image will be adjusted slightly
differently. Instead use neutral RAW conversion settings, and apply any
color correction after stitching.

Kind regards,

New House Internet Services BV
Joost Nieuwenhuijse

-----------------------------------------------
PTGui - Photo Stitching Software

www.ptgui.com
For support see: http://www.ptgui.com/faq/
-----------------------------------------------

> Dropbox, sendspace.com <http://sendspace.com>, or similar file

> sharing facility if necessary.
>
> John
>

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[Erik Krause]

Am 27.05.2017 um 03:19 schrieb tel...@gmail.com:
> Some things that may help, when help is needed: reducing contrast within
> the camera itself, if available

This should have no effect when shooting raw.

[...]

> ignoring the Vignetting correction in Camera Raw and instead eliminating
> obvious dark corners with the Spot Removal Brush;

Vignetting correction (or other non-global brightness changes) prior to
stitching will throw off PTGui's own vignetting optimization, which is
much better than any raw converter could be, since it determines the
vignetting from the overlap.

--
Erik Krause

[John Houghton]

On Saturday, May 27, 2017 at 6:05:48 AM UTC+1, PTGui Support wrote:

Hi Rob,

Have you tried doing the vignetting correction in PTGui Pro?
See https://www.ptgui.com/examples/vigntutorial.html
and disable all corrections in Camera RAW to prevent it from interfering.

Joost, To what extent will vignetting correction be compromised by clouds changing position significantly between shots?  Would there be any advantage in saving a vignetting curve from a cloudless sky panorama and loading that in?

John

[lione...@gmail.com]

Here’s my experience with banding as illustrated in the images posted.

First of all, I often get similar banding even when I shoot in full manual mode - and I do sometimes forget.  When I view my image in the PTGui Detail Viewer in the “No Blend” mode, I will often see that the tone of the source images varies somewhat from image to image, even though they are all the same ISO, aperture and shutter speed.  I understand there will be some natural variation in outdoor lighting, but I am surprised at the magnitude of the variation.  What I do is adjust the values in the EXP Offset column in the Image Properties tab.  It is laborious, but it solves the problem.  I find that I generally need small values in the range +0.3 to -0.3 to lighten/darken an individual source image.  PTGui saves these values in the project file, so I don’t have to figure it out again if I have to re-stitch the image.  Perhaps my eyes deceive me, but I find the banding most noticeable with the image displayed at a small size - so the banding is more obvious in the thumbnail than with the image at 50%.

My shutter speeds tend to be faster because I try to shoot at larger apertures in order to get faster shutter speeds.  That’s largely a matter of taste, because lots of my images include water, and I prefer to render ripples and waves realistically rather than “silk” them.  I’m shooting with a Nikon D300, almost exclusively in Portrait orientation; by far the majority of my stitched images are captured at 50mm or 105mm (prime full frame lenses on a crop sensor body).  I only shoot RAW, develop to .tiff for PTGui using ACR, always 16-bit mode, develop settings identical for all images in the same pano.

The most troubling form of uneven exposure I encounter results in a vertical gradient in some of my source images.  I have no idea why this happens, and it is intermittent.  The best solution I have found for this is to adjust Post Crop vignetting when developing the source images in Camera RAW - positive values, effectively lightening the corners of the images.  Matthew, you could try this.

[lione...@gmail.com]

Rob, I've seen several people come to this forum and speak highly of Photoshop’s blending.  I’m afraid I cannot agree; perhaps that’s just the nature of the images I make, but recent experiments with it have refreshed my disdain.

If a stitched image does NOT require any post-stitch editing (in my experience this means there are no moving elements in the image), you might find it satisfactory.  A recent test with an image like this left me very frustrated because I was unable to straighten the image - and I tried every Photoshop tool I know, including Adaptive Wide Angle.

The vast majority of my images have water in motion, so the minimum I have to do is clean up the seams in the water.  If there’s a boat, it becomes a different game, especially if the boat is too large to fit in a single frame.  So my reality is that I take the layered stitched image into Photoshop, and edit it.  During my recent experiments I stitched an image like this in Photoshop CC, and then I tried to edit it as I did for that same image stitched in PTGui.  And then I got a nasty surprise: the masks that Photoshop constructs to create the blended composite overlap where one image meets another.

The problems I ran into include:

1. There’s no simple way to trace an element in the blended composite back to the source image.
2. If you edit the blended composite by painting on one of the masks, you have to figure out how to deal with the fact that the masks overlap.
3. The way PhotoShop organizes layers in the blended composite militates against editing the layer masks, so you are left with cut (to extract material for the repair) and overlay; tough way to deal with a seam in water.
   

I gave up.

Just to be clear, when I say that the masks overlap I mean that they do not butt up against each other at a seam, pixel to pixel.  Make a selection from one mask, intersect that with the selection from another mask with a common edge, and you will find there’s an overlap of several pixels.  It seems to vary, but it’s in 10px or less.

There may well be a smarter way to blend, but I doubt it’s Photoshop - at least, not the current release of PhotoShop CC.

Those who are curious can see some of my stitched images at the gallery “Collected Panoramas” at http://lesapi.photoshelter.com/gallery-collection/Collected-Panoramas/C00003rjP3wgTeU4 (the web site is www.lesapiimages.com and it’s the source of a certain amount of frustration).

Regards
Lionel

[John Houghton]

On Saturday, May 27, 2017 at 11:15:53 PM UTC+1, lione...@gmail.com wrote:

First of all, I often get similar banding even when I shoot in full manual mode - and I do sometimes forget.  When I view my image in the PTGui Detail Viewer in the “No Blend” mode, I will often see that the tone of the source images varies somewhat from image to image, even though they are all the same ISO, aperture and shutter speed.  I understand there will be some natural variation in outdoor lighting, but I am surprised at the magnitude of the variation.  What I do is adjust the values in the EXP Offset column in the Image Properties tab.  It is laborious, but it solves the problem. 

In difficult cases, I frequently make use of graduated selections in Photoshop to adjust the brightness at one side of an image without affecting the opposite side. I have an old tutorial here: http://www.johnhpanos.com/gradtut.htm .  Another tip is to add a temporary curves adjustment layer to a layered file to greatly increase the contrast to make any banding much more visible.

John

[Roger D Williams]

I would just like to add my own experience along these lines. I had a similar problem with banding, and I also prefer to use high shutter speeds. I sometimes found left-to-right gradients in the sky, and these "steps" in brightness were responsible for banding, although I had to cycle through several other possible causes and cures before confirming this. The problem was the uneven speed of the focal plane shutter traveling across the sensor. I was able to rescue the panoramas (which were of the IVRPA meeting in Prague) by using PhotoShop gradients, as John has suggested.

I was able to reduce the effect of shutter speed by avoiding a synch setting for flash that I had set unintentionally without knowing how it might affect shutter movement. I forget what it was, as I never use flash and therefore never need to bother with synch. Sorry not to be more help, but this might be a clue for something that would be worth checking...

Roger Williams

Sent from my iPad

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[PTGui Support]

Hi John,

I don't think it's an issue. You would normally have at least 5 images
in a panorama, the mismatch would only affect a few percent of the
samples used for vignetting calculation. And the optimization is
somewhat resilient to outliers.

Kind regards,

New House Internet Services BV
Joost Nieuwenhuijse

-----------------------------------------------
PTGui - Photo Stitching Software

www.ptgui.com
For support see: http://www.ptgui.com/faq/
-----------------------------------------------

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[Erik Krause]

Am 28.05.2017 um 00:15 schrieb lione...@gmail.com:

> I will often see that the tone of the source
> images varies somewhat from image to image, even though they are all the
> same ISO, aperture and shutter speed.

I assume you also use fixed white balance. Otherwise this would account
for slight differences.

> My shutter speeds tend to be faster because I try to shoot at larger
> apertures in order to get faster shutter speeds.

What is faster? Uneven shutter curtain movement, which is the usual
reason for brightness differences in one image, starts at about 1/250s
(unless your camera is very cheap or defective). At 1/1000s or faster
even good cameras will show some uneven brightness, since at that speed
it's only a narrow slit moving across the sensor.

1/250s is the time where the opening curtain is fully open before the
closing curtain starts to move for most cameras. Water ripples will
still be sharp at 1/100s, so you don't need to be faster.

For waterfalls or mountain streams you need faster times of course, but
a completely frozen waterfall looks unreal IMHO. There is a wide range
between frozen and silky. I don't go beyond 1/250s because I like some
dynamic in the water. See f.e.
www.360cities.net/image/cascade-de-runes-lozere-languedoc-roussillon

Stopping down a bit will get you more sharpness due to depth of field
increase and reduced lens aberrations.

--
Erik Krause

[lione...@gmail.com]

Erik, yes, I set white balance the same across the set of images in the stitch, based on a colorchecker reference shot which I usually remember to shoot with the images.

As to shutter speed, I take what I can get, don't have a preferred value.  Since my D300 dates back to 2008, it may need adjustment, but I date back even further so that's a delicate subject.

Joking aside, I start by choosing an aperture that enables me to shoot at the hyperfocal distance for the scene, and I will go with large apertures such as f/2.8 when the distances permit it.  I then set shutter speed by watching my exposure meter while panning across the scene.  I bracket by varying shutter speed.  The natural variation in lighting across large scenes often means that some of my source images are a little underexposed, other somewhat overexposed, but it's seldom problematic as I can compensate in PTGui as mentioned earlier.

By way of example, the source images for the last 3 panos in my "Panoramic views of the Cape Peninsula, South Africa" gallery were shot at shutter speeds ranging from 1/500 to 1/1000.  I can't display the EXIF information on that web site, but I can tell you that the stitches used the images captured at 1/1000, 1/1000 and 1/500 respectively.

Regards
Lionel

[lione...@gmail.com]

Thanks for the reminder, John, I'll take a look at your tutorial.  Perhaps that will help me find a way to mitigate some of the gradients I have trouble with.

Regards
Lionel

[lione...@gmail.com]

John, I'm going to try this the next time a gradient makes my life difficult.

Thanks
Lionel

[Erik Krause]

Am 28.05.2017 um 18:25 schrieb lione...@gmail.com:
> By way of example, the source images for the last 3 panos in my "Panoramic
> views of the Cape Peninsula, South Africa" gallery were shot at shutter
> speeds ranging from 1/500 to 1/1000.

That wouldn't be necessary for that subject, 1/100 or 1/250 would be
enough. Better shoot at lower ISO instead, which will give you a
slightly higher dynamic range anyway.

The short times could well be the reason for the banding. Can you make
two or three source images that show the banding available for download
somewhere for investigation?

--
Erik Krause

[lione...@gmail.com]

Erik, I apologize for my slow response.

As far as I can tell the banding is not apparent in any one source image, but when you see them side by side the gradients become apparent.

I will look for an example and get back to you.

Regards

[lione...@gmail.com]

Erik, I think I mentioned this but in case not, I shoot everything at the lowest ISO my D300 offers, nominally ISO 100.

I think I don't have issues with sharpness either, but that, of course depends on one's eyesight.

I have placed some images in a private gallery called "Oudekraal for PTGui" located at  http://archive.lesapiimages.com/gallery/Oudekraal-for-PTGui/G0000bp4hUKTplt0

You will need to enter this password (one space between words): PTGui Discussion

The first image is a 750px X 750px crop from the full size image, showing the area bounded in red on the second image (downsized).  The third image is a snapshot from Google Maps showing the vantage point and distance to a feature in the crop.  The crop shows a Rotair cable car that takes 65 people ant a section of the cables on which it travels to the lower cable station on the other side of Table Mountain.

[Rob Holmes]

Did you guys ever solve the banding issue? It's plaguing me also. I'm stitching 29 images from a DJI Mavic Pro. The exposure settings are all Manual and set with a histogram. There is no "auto" anything being used. 

I've supplied a stitch of the horizon images done in Photoshop and it's perfect. I've supplied a stitch of the images from PTGui 11.5 and it has the normal offending banding. I followed the vignetting guide listed above and it had little effect. 

[Erik Krause]

Am 16.07.2018 um 00:12 schrieb Rob Holmes:
> I've supplied a stitch of the horizon images done in Photoshop and it's
> perfect. I've supplied a stitch of the images from PTGui 11.5 and it has
> the normal offending banding. I followed the vignetting guide listed above
> and it had little effect.

Stitch with PTGui but auto blend with photoshop. For full sphericals use
my Auto Blend 360 script:
http://www.erik-krause.de/ttt/#Auto%20Blend%20360%20Javascript

[PTGui Support]

Hi Rob,

It looks like vignetting. Perhaps the over exposed sky is preventing the
vignetting algorithm to work properly. Could you make your images
available for download so I can look?

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

> <https://lh3.googleusercontent.com/-kmNnII1FIGI/W0vGjyR2GpI/AAAAAAAAC-k/rIWg2bLq7o8jxl5Px4Iz0USzqulMC8IOgCLcBGAs/s1600/PTGuiBanding.jpg>

>
>
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[Erik Krause]

Am 16.07.2018 um 09:09 schrieb PTGui Support:
> It looks like vignetting. Perhaps the over exposed sky is preventing the
> vignetting algorithm to work properly.

But why is the sky in the PTGui example overexposed but not in the
photoshop example?

Rob, did you by chance use raw images directly in PTGui?

[Avijobo]

On Monday, 16 July 2018 09:06:40 UTC+2, Erik Krause wrote:

Stitch with PTGui but auto blend with photoshop.

--
Erik Krause
http://www.erik-krause.de

This advice worked perfectly, much better result! Thanks 

[Dave Giood]

Hi, first time post here. I have also encountered this problem and I don't think lens vignetting was not the problem (CV65/2 @f/8). I don't have the Pro version so tried a demo and was able to correct with the Vignetting correction tool. Just for fun I ran the same images through Affinity Photo and to my surprise the sky stitched perfectly without any dark bands. I will likely upgrade to the Pro anyhow but thought this might be of interest to others.

Dave

[Paul Hogenboom]

Dear friends, thanks for the reply and suggestions. 

I got a real good support by reading this,

“ You should follow the steps outlined in 7.12:
https://www.ptgui.com/support.html#7_12 “.

This concerns handheld exposures And

shots taken from a tripod.

regards,

Paul