Peter Gawthrop wrote:
> Hi David,
> 
>  just to add my thoughts.
> 
>   1. I use --wExposure=1 --wSaturation=0 --wContrast=0 with enfuse to
>      minimise haloes.

Additionally specify -l 29

>   2. Although I am a fan of enfuse (see "Image Blending with enfuse"
>      at http://www.lightspacewater.net/Tutorials/) there are times
>      when tonemapping works better.
> 
>      http://viewat.org/?hd=1&i=en&id_aut=139&id_pn=3210&sec=pn shows a
>      panorama composed of images preblended with enfuse from 6 2-stop
>      exposure bracketed jpegs --  parameters as in 1.
> 
>      http://viewat.org/?hd=1&i=en&id_aut=139&id_pn=3226&sec=pn uses
>      the same inmages merged to hdr with Debvec's hdrmerge and Erik
>      Reinhard's tm_photographic. 

The enfused one looks much better - or did you ever see turquoise clouds?

>      The images a quite similar in quality, but, if you look straight
>      up, the rendering of the silver leaves agains the sky is _much_
>      better with the tone-mapped version, whereas enfuse turns some
>      leaves black.

I think the images are rather different in quality. The enfuse versions 
resembles far more the appearance of the Victoria forests like I 
remember and shot them on slide film during my visit to Australia 10 
years ago. The turquoise cast in the tonemapped version is pretty 
annoying - no eucalyptus tree has such a bark.

But I agree that some leaves may appear darker in the enfused version. 
This is by the very nature of the algorithm. It preserves local contrast 
and reduces global one. This is the only possibility to deal with really 
high dynamic range. All locally working tonemapping algorithms do that, 
but I found none which does it that subtle like exposure fusion.

For the visual appearance this usually isn't a problem, since our eyes 
do just the same: The immediate dynamic range one can perceive is about 
5 to 8 f-stops. But the total dynamic range our eyes can adopt to in few 
microseconds is up to 21 f-stops.

>      Does anlyone know how to stop enfuse doing that? Or is it
>      inhernet in the method.

You can use less levels, but this might cause halos around larger dark 
structures. If you think you need those lighter leaves you will need to 
manually blend them in. But in reality any small dark objects look black 
against a bright background...

On the other hand the subject is well within the range of a global 
tonemapper which doesn't have halo problems. If I remember correctly, 
tm_photographic is a global tonemapper, hence it might be the right 
choice for that kind of images.

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

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