Prioritize usability over anything else, exemplified by the Edge Preserving Decomposition implementation

[Beep6581]

Originally reported on Google Code with ID 2601

I want to give an example of what I see as a mistake in the implementation of RawTherapee's
"Tone mapping" tool. The reason is for the same mistake not to be made when designing
other tools, and to maybe encourage someone to try their hand at re-implementing EPD.

http://www.cs.huji.ac.il/~danix/epd/

If you take a look at the Edge-Preserving Decompositions for Multi-Scale 
Tone and Detail Manipulation video presentation, 03:33 into the video, you can see
they change the effect smoothly in real time. As far as I know, it can do that because
it precomputes images for the fine/medium/coarse levels and then just blends between
via slider control, something which can be done smoothly and in real time. RawTherapee's
EPD implementation offers a few more sliders - ones which are of no use because they
are prone to artifacts and their <100% preview is completely inaccurate. On top of
this, slider manipulations are slow. I would much rather click a button, wait a few
seconds for the three levels to be computed and then be able to smoothly blend between
them in real time with an accurate preview, than what we have. That would be far more
usable, and in the end it's all about usability.

Another point: RT's EPD sliders offer almost infinite fine-grained control, yet who
needs it? From what I read, I seem to be one of very few people who can actually use
RT's tone mapping because others complain that they can't get satisfactory results
using it. I agree, it takes many hours of practice to learn to get aesthetically pleasing
results, because you need to fiddle very precisely with the curves to control EPD,
and then you still have to save a few downscaled versions to make sure the saved image
looks like what you want. And all this time I find myself rarely using the Edge Stopping
slider - three levels would be more than enough - and I don't/can't use the Scale and
Reweighting Iterates sliders because for any settings which differ significant from
their default values they are effectively broken, artifact-ridden. Another example
of how less could be more.

Reported by entertheyoni on 2014-12-10 12:07:13

[Beep6581]

Maybe I am the second person to use Tone Mapping. I usually use it along with small
changes in Shadows when I want to generally brighter darker areas. I use the Tone Mapping
strength between 0.02 - 0.07 and Reweighting iterates at 3 or 4. I have not generally
touched the Edge Stopping slider. entertheyoni's suggestions sound reasonable to me.

Reported by dnw3039 on 2014-12-14 20:15:11

[Beep6581]

Well I'm definitely NOT one of the people who can use Tone Mapping - in fact it's one
of my pet hates. For me, the fact that it has a slider "Reweighting Iterates" means
that something is very wrong - photographers shouldn't have to mess about with the
internals of image processing algorithms they cannot understand.

End of rant.

Reported by anthonyefarr on 2015-01-28 10:00:10