Re: [darktable-user] What do the sliders of the local contrast tool actually do?

[Ari Torhamo]

Hi Rafa,

Thanks for the tip. I tried that, and it brings interesting results. Not 
very easy to interpret, though, when the aim is to understand how 
'contrast' and 'detail' work together and affect each other. Experience 
will probably help. Anyway, undoubtedly a useful tool to have in the 
toolbox in many situations.


-Ari-

27.12.2016, 21:33, Rafa García kirjoitti:

Hi,

When I want to know what I'm changing I change blend mode to 
difference and it shows a black background with white/grey points 
indicating changes.


Regards

PS: sorry Johannes for the email

Enviado desde mi tabla de planchar


El 27 dic. 2016 6:22 p. m., "Ari Torhamo" > escribió:



Hello,

I've been trying to find out what the different sliders on the
local contrast tool actually do in Darktable. There are three
sliders and the working of the first one seems obvious; it adjusts
the radius (in pixels?) of the area the other sliders affect on.

The contrast slider doesn't seem to do anything if the detail
slider is in zero position. In other positions both sliders change
contrast, although differently, the detail slider having a
stronger effect. I'd like to know what these two sliders actually
do. I've been testing and observing their working on different
photos, but I still feel that there's too much trial, error and
confusion involved in using them.

I'm not asking for mathematical formulas (although they might be
interesting, if I'd understand them), but rather a clear
explanation in plain English. The explanation on the Darktable
user manual is very vague, and a good amount of googling didn't
help either.

I hope someone in the know can take the time to answer this.
Perhaps the answer could be used to improve the user guide. Thanks
in advance!

Ari Torhamo

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Re: [darktable-user] What do the sliders of the local contrast tool actually do?

[Ari Torhamo]

27.12.2016, 20:46, johannes hanika kirjoitti:

hi,

sorry i don't have an english explanation, only the formulas.

this module enhances local contrast by using
``Unnormalized bilateral filtering''
as described in
http://people.csail.mit.edu/hasinoff/pubs/AubryEtAl14-lapfilters.pdf
(the rest of the paper is implemented in a branch).
Are you sure that paper isn't about the wave functions of quantum 
mechanics? ;-)

the detail slider is mapped to the amount the difference to the base
image will be multiplied by.
Difference caused by what?  Multiplied by what? Sorry, I'm sure it's 
just me, but I don't even know what refers to what in the above sentence.

the backend uses the bilateral grid.

Suddenly the veil was lifted and everything became crystal clear...

Thanks for trying. I'll just push the sliders around and try to come up 
with something that looks good :-)


-Ari-


On Wed, Dec 28, 2016 at 6:21 AM, Ari Torhamo  wrote:

Hello,

I've been trying to find out what the different sliders on the local
contrast tool actually do in Darktable. There are three sliders and the
working of the first one seems obvious; it adjusts the radius (in pixels?)
of the area the other sliders affect on.

The contrast slider doesn't seem to do anything if the detail slider is in
zero position. In other positions both sliders change contrast, although
differently, the detail slider having a stronger effect. I'd like to know
what these two sliders actually do. I've been testing and observing their
working on different photos, but I still feel that there's too much trial,
error and confusion involved in using them.

I'm not asking for mathematical formulas (although they might be
interesting, if I'd understand them), but rather a clear explanation in
plain English. The explanation on the Darktable user manual is very vague,
and a good amount of googling didn't help either.

I hope someone in the know can take the time to answer this. Perhaps the
answer could be used to improve the user guide. Thanks in advance!

Ari Torhamo

darktable user mailing list
to unsubscribe send a mail to darktable-user+unsubscr...@lists.darktable.org




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to unsubscribe send a mail to darktable-user+unsubscr...@lists.darktable.org

Re: [darktable-user] What do the sliders of the local contrast tool actually do?

[Rafa García]

Hi,

  When I want to know what I'm changing I change blend mode to difference
and it shows a black background with white/grey points indicating changes.

Regards

PS: sorry Johannes for the email

Enviado desde mi tabla de planchar


El 27 dic. 2016 6:22 p. m., "Ari Torhamo"  escribió:


Hello,

I've been trying to find out what the different sliders on the local
contrast tool actually do in Darktable. There are three sliders and the
working of the first one seems obvious; it adjusts the radius (in pixels?)
of the area the other sliders affect on.

The contrast slider doesn't seem to do anything if the detail slider is in
zero position. In other positions both sliders change contrast, although
differently, the detail slider having a stronger effect. I'd like to know
what these two sliders actually do. I've been testing and observing their
working on different photos, but I still feel that there's too much trial,
error and confusion involved in using them.

I'm not asking for mathematical formulas (although they might be
interesting, if I'd understand them), but rather a clear explanation in
plain English. The explanation on the Darktable user manual is very vague,
and a good amount of googling didn't help either.

I hope someone in the know can take the time to answer this. Perhaps the
answer could be used to improve the user guide. Thanks in advance!

Ari Torhamo

darktable user mailing list
to unsubscribe send a mail to darktable-user+unsubscr...@lists.darktable.org


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to unsubscribe send a mail to darktable-user+unsubscr...@lists.darktable.org

Re: [darktable-user] What do the sliders of the local contrast tool actually do?

[johannes hanika]

hi,

sorry i don't have an english explanation, only the formulas.

this module enhances local contrast by using
``Unnormalized bilateral filtering''
as described in
http://people.csail.mit.edu/hasinoff/pubs/AubryEtAl14-lapfilters.pdf
(the rest of the paper is implemented in a branch).

the detail slider is mapped to the amount the difference to the base
image will be multiplied by.

the other two are the range sigma (contrast slider, colour distance, L
channel only in this implementation) and the spatial sigma (radius,
pixel distance).

the backend uses the bilateral grid.

cheers,
 jo


On Wed, Dec 28, 2016 at 6:21 AM, Ari Torhamo  wrote:
>
> Hello,
>
> I've been trying to find out what the different sliders on the local
> contrast tool actually do in Darktable. There are three sliders and the
> working of the first one seems obvious; it adjusts the radius (in pixels?)
> of the area the other sliders affect on.
>
> The contrast slider doesn't seem to do anything if the detail slider is in
> zero position. In other positions both sliders change contrast, although
> differently, the detail slider having a stronger effect. I'd like to know
> what these two sliders actually do. I've been testing and observing their
> working on different photos, but I still feel that there's too much trial,
> error and confusion involved in using them.
>
> I'm not asking for mathematical formulas (although they might be
> interesting, if I'd understand them), but rather a clear explanation in
> plain English. The explanation on the Darktable user manual is very vague,
> and a good amount of googling didn't help either.
>
> I hope someone in the know can take the time to answer this. Perhaps the
> answer could be used to improve the user guide. Thanks in advance!
>
> Ari Torhamo
> 
> darktable user mailing list
> to unsubscribe send a mail to darktable-user+unsubscr...@lists.darktable.org
>

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