HDR deghosting does not appear to be removing ghosts at all?  

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Photonicwand
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HDR deghosting does not appear to be removing ghosts at all?

by Photonicwand » Fri May 10, 2013 7:53 am

Hi there,

I am trying to create a panorama in autopano made up of 7 images of 3 bracketed (+2,0,-2) shots each, 21 shots in total. I imported the raw pictures into autopano, created image stacks of three photos each and then selected the "fusion" and "HDR ghosts" options before rendering the panorama into a 16 bit tiff output. The output is a tonemapped HDR and was the result I was looking for except that the panorama is full of ghost images.

It almost seems as the HDR deghosting does not do anything at all: if the people are only on one layer, they are faintly visible above the background and when people moved they are looking unsharp from the movement. This problem is not just in one or two places but everywhere across the panorama.

I have read through some of the discussions on the forum around challenges with the HDR deghosting, but usually the issue seemed to be that the deghosting does not work as well as expected. In this case, the HDR deghosting does not appear to do anything at all. I cannot imagine that there is an "HDR ghosts" option in the software that is completely not working, so I assume I must be doing something wrong. Is there an option that I missed somewhere?

Any advice is appreciated.

Below screenshots of the blend settings I used as well as the output image and some specific details as illustrations of the problems.













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by marzipano » Fri May 10, 2013 8:40 am

There have been a number of previous threads around this topic and if I am correct, APG 3.0.5 will perform the standard anti-ghosting and alignment in a horizontal direction (i.e. on the overlapping seams along a panorama) in HDR/fusion mode but not in a vertical direction (i.e. on the multiple images of a bracketed set)

This is a serious shortcoming IMO and goes a long way to explain why this function is not currently widely used for outdoor or moving scenes in HDR/fusion whereas rival products such as Photomatix contain these features

FWIW this would be my No1 on the future product development list !

best
Martin

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by klausesser » Fri May 10, 2013 12:08 pm

Photonicwand wrote:Hi there,

I am trying to create a panorama in autopano made up of 7 images of 3 bracketed (+2,0,-2) shots each, 21 shots in total. I imported the raw pictures into autopano, created image stacks of three photos each and then selected the "fusion" and "HDR ghosts" options before rendering the panorama into a 16 bit tiff output. The output is a tonemapped HDR and was the result I was looking for except that the panorama is full of ghost images.

It almost seems as the HDR deghosting does not do anything at all: if the people are only on one layer, they are faintly visible above the background and when people moved they are looking unsharp from the movement. This problem is not just in one or two places but everywhere across the panorama.

I have read through some of the discussions on the forum around challenges with the HDR deghosting, but usually the issue seemed to be that the deghosting does not work as well as expected. In this case, the HDR deghosting does not appear to do anything at all. I cannot imagine that there is an "HDR ghosts" option in the software that is completely not working, so I assume I must be doing something wrong. Is there an option that I missed somewhere?

Any advice is appreciated.

Below screenshots of the blend settings I used as well as the output image and some specific details as illustrations of the problems.

Hi!

Besides a common knowledge that bracketing shouldn´t - naturally - be used with moving objects you should try the automatic/manual masking feature in Photomatix to remove the ghosts before stitching.

You might try to lengthen the time between the brackets while shooting, so that objects are not close together and overlapping each other but have a distance between them - which allows to edit them more easy.

APG´s features regarding HDR/fusion are rather rudimental in my eyes.

So my suggestion is - as always - to process bracketed sets FIRST in a dedicated HDR-application and only THEN stitch the mapped images.

best, Klaus
Simplicity is the keynote of all true elegance. Coco Chanel

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by hermer-blr » Fri May 10, 2013 2:02 pm

To Photonicwand:

Here is my recipie to stitch perfect panoramas with moving people in HDR with APG ((APG, exposure fusion, no need to use Photomatix):

http://www.kolor.com/forum/p108992-2012-12-20-21-09-06#p108992

It is time consuming but deterministic !

All these panoramas were processed using this methodology:

http://jmh.trp.free.fr/New-York


Note: that I do not import the raw files into APG, but tif files generated from the raw.


Good luck
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by klausesser » Fri May 10, 2013 2:43 pm

hermer-blr wrote:All these panoramas were processed using this methodology:

http://jmh.trp.free.fr/New-York

Yeah - but in photonicwand´s examples the moving objects (persons) seem to be closer than in your NY example!
That can make a big difference!

A way to deal with it is to edit the images of a set in Photoshop first and erasing the objects in all but one image. Than saving the images as .png with an alpha channel for stitching will solve the problem.

best, Klaus
Last edited by klausesser on Fri May 10, 2013 2:48 pm, edited 1 time in total.
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by hermer-blr » Sat May 11, 2013 10:43 am

To Klaus:

My process also work with close persons. What I am actually doing is also erasing the unwanted persons.

1/ Note that I am using ptgui only with the main exposure to create accurate masks: red for what I want to delete and green for what I want to keep.

In itself, the use of ptgui allows me AT FIRST to create a perfect panorama with main exposure pictures, ie without any single ghost (red and green masks).

2/ As a SECOND purpose, I use those masks in the under/over exposed images to delete both the red and green areas; as the persons are moving they do not coincide with the masks and I have also to complete the deletion ; I also delete additional moving feature that may not be present on the main exposures and that woud, if not deleted, appear as ghosts.
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by gkaefer » Sat May 11, 2013 10:51 am

"HDR ghost"....

if you're using stacks of Images use the HDR ghost preset.
but to remove the ghosts use the masking tool. and here not the normal (left green/red Icons) but the right ones.
you only can remove ghosts if Images from the same stack Show on that ghost area no ghost.

so Shooting your brackets it make sens to make an pause of 1-5 seconds between the brackets on one Image Position.
and in really croudy places doing that all automatic is Counter productive, who can predict if one Person will remain as ghost for 1 second or for 50...
so even if I use an robotic head in such Scenes I do my Setup in that way so I can manually Trigger the Image. (pausing the robotic head)

Georg
Last edited by gkaefer on Sat May 11, 2013 10:56 am, edited 1 time in total.

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by klausesser » Sat May 11, 2013 1:12 pm

hermer-blr wrote:To Klaus:

My process also work with close persons. What I am actually doing is also erasing the unwanted persons.

1/ Note that I am using ptgui only with the main exposure to create accurate masks: red for what I want to delete and green for what I want to keep.

In itself, the use of ptgui allows me AT FIRST to create a perfect panorama with main exposure pictures, ie without any single ghost (red and green masks).

2/ As a SECOND purpose, I use those masks in the under/over exposed images to delete both the red and green areas; as the persons are moving they do not coincide with the masks and I have also to complete the deletion ; I also delete additional moving feature that may not be present on the main exposures and that woud, if not deleted, appear as ghosts.

Ok - it seemed to me you were talking about using APG only:

*"Here is my recipie to stitch perfect panoramas with moving people in HDR with APG ((APG, exposure fusion, no need to use Photomatix):"*

best, Klaus
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by Photonicwand » Sun May 12, 2013 10:13 am

Thank you for all the feedback.

To be clear, when I took the original shots, I did not intend to create an HDR photo. I always take bracketed photos as a "safety measure" so I can recover in case photos are over- or under exposed. When I started working on this 360, I found that the church was too washed out in the normal shots and the shadowy areas were too grainy in the dark shots which is why I started to look at HDR to improve the panorama. I like the result of the exposure fusion version except for the ghosts.

I had read some threads about issues with the HDR deghosting on this forum, but did not realize it basically does not work at all to remove HDR ghosts. Martin's explanation clarifies a lot what does and does not work, and I totally agree that this is significant shortcoming of the tool and should be addressed as a priority. IMO this feature should really be part of APG and should not require a separate HDR tool.

I have not used Photomatix in the past and based on your feedback started playing around with it for this photograph. I was very impressed by the automatic deghosting - it removed all the ghosts I was having problems with, which is a good illustration that it is possilbe to do so with these shots and APG should also be able to remove them as well. The resulting panorama worked well, but I have three issues with Photomatix from my initial experimentation:
1. Although Photomatix does batch processing, it does not appear to have the option to automatically deghost when batch processing. This meant I had to do one photo at a time - a nuisance when doing 7 photos, difficult when doing more.
2. A much bigger issue is that I have a problem where the colors and saturation in the preview in Photomatix is significantly different from the colors and saturation in the resulting tif file. So much so that I do not like the resulting panorama as it looks very "flat". My monitor has a wide gammut which could be the cause of the problem. It is color calibrated, but I cannot find any option in Photomatix to set a color profile to use. I have not yet purchased a license for photomatix so am limited in what I can do with the tool and I may need to experiment a bit more.
3. It does not appear to work well in Linux so I had to switch to my windows installation. I prefer software that is compatible with Linux, such as APG.
I appreciate that this is probably not the right forum for Photomatix support so I will look further into those issues seperately, but it does illustrate that using Photomatix as part of the workflow does address the deghosting issue.

I had tried to use the masking tool with the red/green icons in APG but did not find that I could get it to work very effectively.

hermer-blr thank you for sharing your recipe. It sounds effective but very involved especially considering the number of ghosts I have to deal with in this photo so I did not try it.

Georg - I am not sure if I understand your comment about using HDR ghost present if using stacks of images as I thought that is what I was doing.

Johan

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by klausesser » Sun May 12, 2013 11:49 am

Photonicwand wrote:1. Although Photomatix does batch processing, it does not appear to have the option to automatically deghost when batch processing.

It does. It´s in the settings. Do all settings to the point you want to have it. Save the preset. When starting the batch choose the preset you saved.

Photonicwand wrote:2. A much bigger issue is that I have a problem where the colors and saturation in the preview in Photomatix is significantly different from the colors and saturation in the resulting tif file.

Run a test on a set - save the results as TIFFs and look how the grading is.

best, Klaus
Last edited by klausesser on Sun May 12, 2013 11:50 am, edited 1 time in total.
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by Photonicwand » Sun May 12, 2013 12:02 pm

Thanks, Klaus. I will give your suggestions a try.

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by marzipano » Sun May 12, 2013 12:59 pm

Photonicwand wrote:1. Although Photomatix does batch processing, it does not appear to have the option to automatically deghost when batch processing. This meant I had to do one photo at a time - a nuisance when doing 7 photos, difficult when doing more.

I believe you can use the settings alongside "merge into 32 bit HDR file" to control anti-ghosting in batch mode then save these settings but still uncheck the 32bit HDR file box afterwards if you don't want this turned on (and the anti-ghosting settings will still remain)

best
Martin


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