Trying to understand concepts of contrast equalizer. Read the manual multiple times but getting confused.
What does it mean by detail scales? Should scale change based on zoom level? I tried making some changes as manual suggested and putting it in “difference” blend mode. I see changes but failing to relate it with scales.
I also tried using different presets etc. But when I use the preset, picture changes, but module shows the flat graphs so I am failing to understand what exact changes module is making. Is there any way to see the changes made by the module to understand it better - like color balance rgb shows which sliders moved where based on presets.
What dt version are you using? Here (dt4.3 Win11) I see the graph change, eg this screenshot when I set the 'bloom" preset. (mouse is hovering over the module) Edit: this module has been around for a while so any recent version of dt should work the same.
The left side of the graph affects contrast between the biggest details in the image, and the right hand side affects the finest details… put very briefly…
The bars change with zoom…the bars show areas that you can impact if there are only 3 bars then this is the area you can influence beyond that the curve is not sampled… And the bars track with the zoom so that it attempts to keep things relatable …
No, I’m on a weekly windows build from this forum. But that should be irrelevant TBH. I just wanted to check that you weren’t running something cutting edge that might have bugs in it.
Here’s a screencast I just did, where I increase then reduce the local contrast at first a very large detail scale, then a very small detail scale, then inbetween - just in case it helps.
@priort, I’m starting to wonder if I’m missing something… I think I need to read the manual! The bars (these?)
don’t move or change when I zoom…?
Check out Robert’s video above …he explains it well… Basically it means at any zoom…changes that you make past the bars are not generally able to be perceived by the human eye… as you zoom in depending on the detail of the image there will be bars across the whole graph and you will then see changes made to the finest details… its a sort of reference… look in on the video around the 14 min mark… 14-about 15:30…
I don’t think anything much has changed in the contrast eq is quite sometime…maybe some of the processing code might have been optimized from early days but not much else…sharpness is now called edges…
If I understand the concepts correctly, it’s similar (if not the same) as what’s used in the “retouch” module, where you can visualise the different detail scales through the “wavelet decompose” tab (see the manual on how to use that tab).
In the image @priort showed, the bee’s hairs would be on the finest scale, while the shape of the flower petals would be in one of the coarsest scales. The stamen would be intermediary.
Both of these sections (retouch and contrast equalizer) link to another section of the documentation that was specifically written to explain these concepts: darktable 4.0 user manual - wavelets.
I, too, have never fully understood the “bars” on the contrast equalizer. I learned something new!
I think it might be a useful feature to visualize the scales in the wavelet-based modules (similar to the “display wavelet scale” of the retouch module). My current usage of contrast equalizer is a lot of guess-and-check to see if I’m targeting the right features.
+1! Where/when I get contrast equalizer to do what I want (<10% success) I count myself lucky, have any idea how or why it worked or how to use it the next time around.
Here’s an example, one illustrated by use of the available presets. For context: I find presets (where available in a module) are an excellent, invaluable resource in understanding how to “work” a module! They are ‘training wheels’, easy to try and thus learn and correlate to what the manual says about a module.
Selecting “clarity” from the presets enhances local contrast (esp the fine details).
If I also want to add sharpen from the presets I have to forego “clarity”. Why it is not possible to retain the effect of the “clarity” preset?
In my (limited) understanding “clarity” affects local contrast (i.e., Luma). sharpen affect edge awareness (i.e., Edge).
Is this an artifact of the presets? something involving the science underlying the contrast equalizer?
Also, is local contrast moot if you have contrast equalizer in the pixelpipe? if not, is it better for local contrast to follow or precede contrast equalizer?
From what I recall the clarity preset and many in the contrast eq were too strong. I had a preset called clarity muted…that was about 0.33 on the mix slider… I don’t use it much any more I have a few presets in local contrast that I tweak and I use D&S module. I also use the contrast slider in CB module after I set the tone mask…I find it does a nice job of adding contrast…
Yes, the presets in contrast equalizer are not good at all, I have new presets I made to replace all of them.
Incidentally, once you do get the hang of the contrast equalizer, I find it much easier to work with than the diffuse and sharpen module. I know the trend is to have more sliders and fewer fancy UIs in the modules, but sliders can sometimes be just too overwhelming. I want to love the diffuse and sharpen module, and I’ve spent a lot of time trying to learn it, but there are just too many sliders for me and pleasing results are usually achieved by trial and error (and using presets). In the end, I often go back to the contrast equalizer because I can be more deliberate with what I want to achieve. Obviously other people’s experiences will be different.
The bars (these?)