Re: [darktable-user] Questions about darktable exposure fusion

[junkyardsparkle]

On Thu, Feb 23, 2017, at 09:20, Stéphane Gourichon wrote:
 
> * Darktable basecurve fusion always considers only one image at a time. 
> Never "two frames", several input files (be it bracketed exposure, 
> flash/no flash, etc.).

You can, however, use darktable's "create hdr" function to produce a high 
dynamic range image from a bracketed stack, and then process *that* image with 
the basecurve fusion. The disadvantage compared to applying the fusion 
algorithm directly to a stack of images is that it's probably less forgiving of 
slight misalignment of image features.

-- 
jys

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Re: [darktable-user] Questions about darktable exposure fusion

[Colin Adams]

It has for a long time.

On Thu, 23 Feb 2017 at 18:03 Michael  wrote:

> cool darktable now does HDR!
>
> On Thu, Feb 23, 2017 at 12:20 PM, Stéphane Gourichon <
> stephane_darkta...@gourichon.org> wrote:
>
> Hello,
>
> Darktable exposure fusion released after 2.2.0 is interesting. I tested
> it, and as expected it brightened pictures a bit like draco tone mapping
> operator but with more natural colors and different style of controls.
> Great!
>
> LWN wrote about it in A look at darktable 2.2.0 [LWN.net]
>  that (emphasis mine):
>
> In scenarios where the dynamic range of a scene is too wide to be captured
> in a single shot, the photographer can shoot *multiple exposures* (e.g.,
> one to capture the highlights and one for the shadows). Those exposure*s*
> can then be combined
> 
> via darktable's new "exposure fusion" module. In essence, *the two frames
> (or however many were taken)* are stacked together,
>
>
> The link is to
> https://www.darktable.org/2016/08/compressing-dynamic-range-with-exposure-fusion/
>
> I'm somehow confused because the latter link processes only one picture at
> a time.
>
> Please explain if the following assertions are right or wrong and explain:
>
> * Darktable basecurve fusion always considers only one image at a time.
> Never "two frames", several input files (be it bracketed exposure, flash/no
> flash, etc.).
>
> * Darktable basecurve fusion implements
> http://web.stanford.edu/class/cs231m/project-1/exposure-fusion.pdf in the
> restricted case where "sequence" is actually a copy of the same input data
> with digitally boosted exposure.
>
> * Darktable applies "traditional" basecurve upstream (i.e. before, or
> "first, then fed into") of Mertens/Kautz/Van Reeth algorithm.
>
> * In traditional darktable basecurve, the output values for any pixel in
> output image only depends on the input value of that same and only pixel in
> source image, not any surrounding pixel.
>
> * Darktable basecurve fusion is not reducible to an overall
> "meta-basecurve" because, following Mertens/Kautz/Van Reeth algorithm, it
> considers the neighborhood of each pixels in deciding which pixel to take,
> a kind of operation that traditional basecurve does not perform.
>
> * As a consequence, darktable implementation provides the benefit of the
> algorithm in term of rendering perception (preserve natural colours, etc),
> but not the improved noise in dark area of the flash/no-flash option, since
> there is only one input image. That would either need preprocessing of the
> whole algorithm before darktable, or feeding several pictures into
> darktable to implement the whole algorithm.
>
> Thank you in advance for clarification! Probably a number of people will
> benefit.
>
>
> --
> Stéphane Gourichon
>
>
> 
> darktable user mailing list to unsubscribe send a mail to
> darktable-user+unsubscr...@lists.darktable.org
>
>
>
>
> --
> :-)~MIKE~(-:
>
> 
> darktable user mailing list to unsubscribe send a mail to
> darktable-user+unsubscr...@lists.darktable.org
>


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Re: [darktable-user] Questions about darktable exposure fusion

[Michael]

cool darktable now does HDR!

On Thu, Feb 23, 2017 at 12:20 PM, Stéphane Gourichon <
stephane_darkta...@gourichon.org> wrote:

> Hello,
>
> Darktable exposure fusion released after 2.2.0 is interesting. I tested
> it, and as expected it brightened pictures a bit like draco tone mapping
> operator but with more natural colors and different style of controls.
> Great!
>
> LWN wrote about it in A look at darktable 2.2.0 [LWN.net]
>  that (emphasis mine):
>
> In scenarios where the dynamic range of a scene is too wide to be captured
> in a single shot, the photographer can shoot *multiple exposures* (e.g.,
> one to capture the highlights and one for the shadows). Those exposure*s*
> can then be combined
> 
> via darktable's new "exposure fusion" module. In essence, *the two frames
> (or however many were taken)* are stacked together,
>
>
> The link is to https://www.darktable.org/2016/08/compressing-dynamic-
> range-with-exposure-fusion/
>
> I'm somehow confused because the latter link processes only one picture at
> a time.
>
> Please explain if the following assertions are right or wrong and explain:
>
> * Darktable basecurve fusion always considers only one image at a time.
> Never "two frames", several input files (be it bracketed exposure, flash/no
> flash, etc.).
>
> * Darktable basecurve fusion implements http://web.stanford.edu/class/
> cs231m/project-1/exposure-fusion.pdf in the restricted case where
> "sequence" is actually a copy of the same input data with digitally boosted
> exposure.
>
> * Darktable applies "traditional" basecurve upstream (i.e. before, or
> "first, then fed into") of Mertens/Kautz/Van Reeth algorithm.
>
> * In traditional darktable basecurve, the output values for any pixel in
> output image only depends on the input value of that same and only pixel in
> source image, not any surrounding pixel.
>
> * Darktable basecurve fusion is not reducible to an overall
> "meta-basecurve" because, following Mertens/Kautz/Van Reeth algorithm, it
> considers the neighborhood of each pixels in deciding which pixel to take,
> a kind of operation that traditional basecurve does not perform.
>
> * As a consequence, darktable implementation provides the benefit of the
> algorithm in term of rendering perception (preserve natural colours, etc),
> but not the improved noise in dark area of the flash/no-flash option, since
> there is only one input image. That would either need preprocessing of the
> whole algorithm before darktable, or feeding several pictures into
> darktable to implement the whole algorithm.
>
> Thank you in advance for clarification! Probably a number of people will
> benefit.
>
>
> --
> Stéphane Gourichon
>
>
> 
> darktable user mailing list to unsubscribe send a mail to
> darktable-user+unsubscr...@lists.darktable.org
>



-- 
:-)~MIKE~(-:


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[darktable-user] Questions about darktable exposure fusion

[Stéphane Gourichon]

Hello,

Darktable exposure fusion released after 2.2.0 is interesting. I tested 
it, and as expected it brightened pictures a bit like draco tone mapping 
operator but with more natural colors and different style of controls. 
Great!


LWN wrote about it in A look at darktable 2.2.0 [LWN.net] 
 that (emphasis mine):


In scenarios where the dynamic range of a scene is too wide to be 
captured in a single shot, the photographer can shoot *multiple 
exposures* (e.g., one to capture the highlights and one for the 
shadows). Those exposure*s* can then be combined 
 
via darktable's new "exposure fusion" module. In essence, *the two 
frames (or however many were taken)* are stacked together,


The link is to 
https://www.darktable.org/2016/08/compressing-dynamic-range-with-exposure-fusion/


I'm somehow confused because the latter link processes only one picture 
at a time.


Please explain if the following assertions are right or wrong and explain:

* Darktable basecurve fusion always considers only one image at a time. 
Never "two frames", several input files (be it bracketed exposure, 
flash/no flash, etc.).


* Darktable basecurve fusion implements 
http://web.stanford.edu/class/cs231m/project-1/exposure-fusion.pdf in 
the restricted case where "sequence" is actually a copy of the same 
input data with digitally boosted exposure.


* Darktable applies "traditional" basecurve upstream (i.e. before, or 
"first, then fed into") of Mertens/Kautz/Van Reeth algorithm.


* In traditional darktable basecurve, the output values for any pixel in 
output image only depends on the input value of that same and only pixel 
in source image, not any surrounding pixel.


* Darktable basecurve fusion is not reducible to an overall 
"meta-basecurve" because, following Mertens/Kautz/Van Reeth algorithm, 
it considers the neighborhood of each pixels in deciding which pixel to 
take, a kind of operation that traditional basecurve does not perform.


* As a consequence, darktable implementation provides the benefit of the 
algorithm in term of rendering perception (preserve natural colours, 
etc), but not the improved noise in dark area of the flash/no-flash 
option, since there is only one input image. That would either need 
preprocessing of the whole algorithm before darktable, or feeding 
several pictures into darktable to implement the whole algorithm.


Thank you in advance for clarification! Probably a number of people will 
benefit.



--
Stéphane Gourichon



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