[Digikam-users] A modern auto-fix?

Paulux nvlplx at yahoo.fr
Sat May 17 15:36:47 BST 2014

Dear Paul,

You're right about the behavior of camera within the light. But you're wrong 
for ohter items. 

Firtly, DK local contrast tool doesn't remain mid and hight tones, their local 
contrast is modified too, as far as I've experienced (but I admit that I've 
tried differents adjustments and I use 2 parallel lines of adjustments)

Secondly, the page suggested by Gilles is interesting, but the expression 
"tone mapping" is an abuse. Tone mapping is strictly the process to 
transform an HDR picture in a LDR one. The doc linked by Gilles is about an 
emulation of the rendering of some tone mapping algorythms, but not a 
real tone mapping one. 

Nevertheless, I really love the local contrast dK tool, which is a faboulus 
tool. Thank you Gilles ;-)


Le samedi 17 mai 2014, 09:56:02 Paul Verizzo a écrit :

    Well, just        as I start to think it's a matter of semantics, now I'm really        
confused.                  I agree that the human eye has no problem, let's 
say, seeing        good detail in shadows.  But the camera can't capture 
that        dynamic range, so it shuts the shadows down in favor of mid and        
high tones.  But the data is still there in the shadows, just        like with 
slide film.                So, yes, the dK Local Contrast tool does certainly look 
at the        (lack of) shadow contrast and, um, locally, increases it in the        
low dynamic range areas, and leaves the mid and high tones        alone.  
Not that dK needs to mimic Photoslop terminology, but        they are the 
big boys out there, and Local Contrast means what        we used to call in 
film developing characteristics, "Micro        contrast."  (A chemical Unsharp 
Mask using border effects!) Best        as I can see, anyway.                 As to 
what you say, Paulux,  "The tone mapping process......", I        guess it's 
the old "If it walks like a duck....." thing.  Even        the page Giles 
suggested, which I had found earlier,        
http://zynaddsubfx.sourceforge.net/other/tonemapping/[1] calls the        
function "Tone Mapping" and says that "Local Contrast" is a        function 
within it.                Regardless, I'm very glad it's there.  As always, so 
grateful to        the dK team!                Paul                           
On 5/17/2014 8:57 AM, Paulux wrote:        
"Local contrast" is adjust and optimize        contrast inside local zones of a 
picture in order to approach        human eyes perception. That's exactly 
what the local contrast        tool in DK does.       
The tone mapping process consists in matching        repartition of colors 
from a 32 bits picture in a 8 bits one        (for instance). That's totally 
different, even if some tone        mapping algorythms have deep influence 
of local contrast.       
Best regards      

It's Windows, Carl, and the          processor is a P.O.S. dual core that was 
meant for a laptop,          but it's in my desktop.  My comment on speed 
was relative to          the Canon program, and even the Windows Phone 
one.  But it's          fine, it is what it is, I'm just grateful for the discovery.                    
On the topic, and further internet research, that the use of          "Local 
Contrast" in dK might be a bit of a misnomer.  As          mentioned, in PS, 
the plug-in does work with local contrast,          not overall tones.  In fact, 
I'm seeing "Tone mapping" being          used for what dK calls "Local 
Contrast."  Seems to be more          accurate, grammatically.                    
Paul Verizzo                         
On 5/17/2014 8:22 AM, Carl McGrath wrote:            
Paul        I scanned quickly for what OS you are running but did not find        
it; I run openSUSE 13.1        dK 4.0.0 arrived a few days ago, with all the 
fixes Gilles        reported that enable multicore.                Local Contrast 
and Sharpness tools now blazing fast(by        comparison)                    
On 05/17/2014 07:58 AM, Paul Verizzo wrote:            
Wow, that's it!                      I finally had time to locate some of the lousy 
original photos          I had successfully improved with a couple of other 
programs,          including, oddly, that Nokia (Windows Phone) Fix.                      
Putzed with dK Local Contrast, works beautifully.  Just what I          was 
after.                      I tried to find information and help in the dK PDF, but 
could          not.  Searching online, "local contrast" brings up a lot of          
Photoslop entries, but they necessitate using layers and          unsharp 
mask.  So much for the expensive program.  If I add          "digikam" to the 
search, I just keep getting repeats from a          blog posting.                    
I'd like to learn how to manually control adjustments for best          results.                    
Any further help to be found?                    Oh, yes.  Kind of slow, but if I 
factor in the need to open          another program, rename, shuffle files, 
Local Contrast is          another dK winner!                    Thanks, Giles (and 
all others!)                    Paul               
On 5/10/2014 12:11 PM, Gilles Caulier wrote:            
digiKam has LocalContrast tool which make the same correction to      
image. In fact it emulate pseudo HDR rendering.      
Gilles Caulier      
2014-05-10 18:07 GMT+02:00 Paul Verizzo <paulv at paulv.net>[2]:       
Background:  I've been in digital photography since 2000, decades of film      
before and since.  I'm certainly familiar with the use of curves to correct      
bad photos.  But so tedious, and if the photos are snapshots, hard to      
justify the time.  It appears to me, although I can't prove it, that digital      
cameras, discrete or within phones, seem to be doing a much better job      
automatically adjusting curves than my old Minolta A2, for instance.      
I recently became aware of a new free Canon program, My Image Garden, 
has a much improved Auto-fix than its forerunner.  As an example, a backlit      
photo processed in MIG will bring up only the shadows while leaving the      
normal and highlights alone.  It allegedly uses a zone by zone analysis.  It      
is a terrible program in every other regard, clunky interface, bloated, etc.      
But I used it for some recent pics to advantage.      
Some of those pictures were originally on my Windows Phone 8, which I had      
copied to the HD.  Before I deleted them from the phone, I poked around 
the options at that point.  I found an auto-fix, pushed the "button," and my      
jaw dropped.  Literally.  A very dark, underexposed shot made perfect!  This      
feature is within the Nokia programs!  It is so good, I can see myself      
transferring photos from other sources into the phone for correction!  And      
it's fast, even so.      
I went back through the digiKam manual and looked on screen, and I see 
old standbys there, but nothing like what I've experienced with the above.      
Oh, upon lots of research, I found a 2007 $40 program called Photoright 
upon test, seems to be doing similar zone adjustments.      
Bottom lines:  Are my observations valid?  Do you think DK might get      
something like this?  Oh, yes, all Windows although MIG is available for      
Thanks, Paul Verizzo      
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Digikam-users at kde.org[3]      
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