Help with bracketing and exposure fusion  

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marzipano
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Help with bracketing and exposure fusion

by marzipano » Sun Sep 30, 2012 3:49 pm

Until recently I only had a camera with "Auto" settings and my panoramas were usually hand-held single-row efforts of landscapes

Lucky me ! I now have a camera capable of manual control, RAW images and bracketing.

I have been trying to get APG 3.0B to do Exposure Fusion on a bracketed image using -2 0 +2 stops (just a single image in this example not a panorama) but I have been having problems

Whatever settings I have tried for Optimization and Rendering (anti-ghost, Exposure Fusion, HDR Output etc) - I'm still experimenting with the use of some of these - I always get the problem of small variations in tree foliage caused by the breeze appearing from all 3 images superimposed

The example below shows this

I have tried using Photomatix as a pre-processor and then the problem is solved (see below) but I thought APG could do the same without the use of Photmatix. Is that true ?

I was wondering whether masking would help but wouldn't it be difficult to work out which specific images to mask and where to position the masks without destroying the fusion itself

any help appreciated !

Martin





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hermer-blr
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by hermer-blr » Sun Sep 30, 2012 4:01 pm

I practice exposure fusion with APG. My most issue was to remove ghosts while processing spherical panoramas with APG. In my own case, the ghosts were pedestrians or cars.

My technic is to use the 0 pictures as the reference and make sure that they stitch together without ghosts (due to moving pedistrians or cars) : for this, I will - as necessary - create holes in the pictures (alpha channels & .png files).

Next step will be to erase all the moving parts from the +2 and -2 pictures, in order to avoid any "conflict" between the 0 images and the other ones. Again alpha channels and .PNG files

Then I will stitch the pnaorama with APG (exposure fusion) and the result will be perfect.

Hint : if you generate (and you will have to) a .pano file with you initial tiff or jpg images, then you will have to edit the .pano and change the names of the files to .PNG according to the modifications that you will have performed !

I hope it helps
Nikon D5100 (formerly Nikon D60) - Sigma 10-20 - 24 shots Panoramas in 3 raws
Windows 32 bits - APG
website htt://jmh.trp.free.fr

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by marzipano » Sun Sep 30, 2012 4:56 pm

Thanks hermer-blr

Presumably you could use the new "masking tool" in APG3.0Beta to do the same as removing parts of the images as .PNG files to make "holes"

I can see how that would work OK (but time consuming too!) for cars and people but not so easy for tree leaves, clouds and waves etc

I'll give that a try

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by hermer-blr » Sun Sep 30, 2012 7:14 pm

I have stopped using the deghosting arrow of APG 3 : it does not work with bracketed images and exposure fusion.

You really have to do the work by yourself.

I have never done it with trees and leaves, but the idea is the same: you have to leep them in one single exposure to avoid ghosting effect and erase them (like pedestrians or cars) from the other exposures !

With spherical panoramas, I use PTGUI (demo mode) and its masking tool to accurately determine what needs to be kept or removed; then I export the masks (possible, even in demo version) for further processing with gimp or photoshop. It is very accurate.
Nikon D5100 (formerly Nikon D60) - Sigma 10-20 - 24 shots Panoramas in 3 raws
Windows 32 bits - APG
website htt://jmh.trp.free.fr

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by marzipano » Wed Nov 14, 2012 1:04 pm

I have now discovered why the samples I posted had this ghosting when trying to use Exposure Fusion in APG processing bracketed images (see my original post at the top of this thread)

It turned out (at least in my tests) that it is driven by a setting in the "panorama" settings section called "Layers Editor" / "Default Regroup"

I had this set to "By Stack" and this led to the ghosting but when changed to "Don't Regroup" the ghosting disappeared

Changing this value also seems to have some effect on the overall colour and blending (and not in a good way !) but I still don't relly know what this setting is meant to do


Last edited by marzipano on Wed Nov 14, 2012 1:05 pm, edited 1 time in total.


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