Questions on RAW conversion: Base curve

[Wolfgang Mader]

Hallo list,

I know there is no "correct" way to convert a RAW to e.g. a jpeg, but there is
a unique way which is taken by every camera (perhaps given a specific scene
selection). In my case this would be the Canon EOS 40D. The camera internally
uses a base curve to construct colors which is in most cases far from linear
but specific to the camera model.

My first question is how digikam can know the shape of the base curve. If
digikam does not know the shape, which base curves is applied instead?

If I use the RAW import dialog when opening a RAW in the image editor (F4) I
can pick "Default" to convert the RAW file. Is there a way to use the same
"Default" if I convert RAW files in a queue?

The motivation of this post is my concern, that if I opt for shooting RAW
only, I will not be able to get the "correct" jpg, in the sense the camera
would have done it. This might not even be a valid concern, but you see, it
troubles me... :-)

Thank you for your answers.

Best,
Wolfgang

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[Gilles Caulier-4]

Hi,

2013/9/11 Wolfgang Mader <[hidden email]>:

> Hallo list,
>
> I know there is no "correct" way to convert a RAW to e.g. a jpeg, but there is
> a unique way which is taken by every camera (perhaps given a specific scene
> selection). In my case this would be the Canon EOS 40D. The camera internally
> uses a base curve to construct colors which is in most cases far from linear
> but specific to the camera model.
>
> My first question is how digikam can know the shape of the base curve. If
> digikam does not know the shape, which base curves is applied instead?

There is no base curve analyzed and applied by digiKam. If i'm not too
wrong, base curve can be get from libraw to clien application, but
digiKAm do not get it yet...

The curve settings from RawImport tool is applied after demosaic. It's
not a setting from RAW decoder

>
> If I use the RAW import dialog when opening a RAW in the image editor (F4) I
> can pick "Default" to convert the RAW file. Is there a way to use the same
> "Default" if I convert RAW files in a queue?
>

To apply a curve on your BQM Raw workflow, just add a curve tool on
top of tools list, and save it on a dedicated workflow BQM settings.

Gilles Caulier
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> 2013/9/11 Wolfgang Mader <[hidden email]>:

>> selection). In my case this would be the Canon EOS 40D. The camera internally
>> uses a base curve to construct colors which is in most cases far from linear
>> but specific to the camera model.

the simplest way is to use raw+jpeg in the camera

jdd


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[Gilles Caulier-4]

Jean Daniel is right about RAW+JPEG.

But there are a more faster way. RAW included an embeded version of
JPEG image used for preview mode by camera. This preview image has
generally  alower resolution than a real JPEG file taken in RAW+JPEG.
But this can be enough in certain case.

In BQM, since 3.3.0 (if i remember), i implemented a way to extract
embeded JPEG with RAW workflow. Check BQM queue settings for details.
In this case, there is no demosaicing and processing is very fast.

Gilles Caulier

2013/9/11 jdd <[hidden email]>:

>> 2013/9/11 Wolfgang Mader <[hidden email]>:
>
>
>>> selection). In my case this would be the Canon EOS 40D. The camera
>>> internally
>>> uses a base curve to construct colors which is in most cases far from
>>> linear
>>> but specific to the camera model.
>
>
> the simplest way is to use raw+jpeg in the camera
>
> jdd
>
>
> --
> http://www.dodin.org
>
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[tosca]

2013/9/11 Gilles Caulier <[hidden email]>

In BQM, since 3.3.0 (if i remember), i implemented a way to extract
embeded JPEG with RAW workflow. Check BQM queue settings for details.
In this case, there is no demosaicing and processing is very fast.

Gilles Caulier

I don't know how it does it, but each time I've needed a "quick" JPEG without actually "working" from the RAW, the BQM has given me a pretty good result that I didn't need to modify afterwards.

For me, one more reason to never use RAW+JPEG as Digikam can do the job well and in an instant. :-)

Marie-Noëlle

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[Gilles Caulier-4]

2013/9/11 Marie-Noëlle Augendre <[hidden email]>

2013/9/11 Gilles Caulier <[hidden email]>

In BQM, since 3.3.0 (if i remember), i implemented a way to extract
embeded JPEG with RAW workflow. Check BQM queue settings for details.
In this case, there is no demosaicing and processing is very fast.

Gilles Caulier

I don't know how it does it, but each time I've needed a "quick" JPEG without actually "working" from the RAW, the BQM has given me a pretty good result that I didn't need to modify afterwards.

For me, one more reason to never use RAW+JPEG as Digikam can do the job well and in an instant. :-)

Marie Noelle,

If you don't use RAW Jpeg extraction option in BQM, and if you use "Auto Brightness" option from WB section, libraw will emulate the famous automatic curve from dcraw which give a very good results in 90% of cases.

dcraw only support this automatic mode in 8 bits per color per pixels. I work with libraw team to extend this mode in 16 bits/color/pixels, to have an homogeneous behavior.

Note : if "Auto Brightness" is disable, a linear curve is used instead. This is why raw demosaicing is generally a black hole result on screen, and need post processing curve adjustments, which can be done with Curve tool.

 

Gilles Caulier

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[tosca]

2013/9/11 Gilles Caulier <[hidden email]>

Marie Noelle,

If you don't use RAW Jpeg extraction option in BQM, and if you use "Auto Brightness" option from WB section, libraw will emulate the famous automatic curve from dcraw which give a very good results in 90% of cases.

Gilles,

I'm not sure what "WB section" stands for in that case... not White Balance, I guess? So what module are you refering to? And in BQM or in Edit?

Marie-Noëlle

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[Gilles Caulier-4]

2013/9/11 Marie-Noëlle Augendre <[hidden email]>

2013/9/11 Gilles Caulier <[hidden email]>

Marie Noelle,

If you don't use RAW Jpeg extraction option in BQM, and if you use "Auto Brightness" option from WB section, libraw will emulate the famous automatic curve from dcraw which give a very good results in 90% of cases.

Gilles,

I'm not sure what "WB section" stands for in that case... not White Balance, I guess?

WB = White Balance.

 

So what module are you refering to? And in BQM or in Edit?

Both. Look Raw demosaicing settings. There is a WB section.

Gilles Caulier

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[Elle Stone]

In the digikam raw processing WB section there is "autobrightness"
which sets the white level (Gilles, yes?), which is not the same as
white balance. From the dcraw
manpage,http://www.cybercom.net/~dcoffin/dcraw/dcraw.1.html

COLOR OPTIONS
By default, dcraw uses a fixed white balance based on a color chart
illuminated with a standard D65 lamp.

-w Use the white balance specified by the camera. If this is not
found, print a warning and use another method.
-a Calculate the white balance by averaging the entire image.
-A left top width height Calculate the white balance by averaging a
rectangular area. First do dcraw -j -t 0 and select an area of neutral
grey color.
-r mul0 mul1 mul2 mul3 Specify your own raw white balance. These
multipliers can be cut and pasted from the output of dcraw -v.

OUTPUT OPTIONS
By default, dcraw writes PGM/PPM/PAM with 8-bit samples, a BT.709
gamma curve, a histogram-based white level, and no metadata.

-W Use a fixed white level, ignoring the image histogram. (Gilles,
this is autobrightness in the digikam raw processor, yes?)

This latter is the white level, not the white balance. The
corresponding line of dcraw code reads:

perc = width * height * 0.01; /* 99th percentile white level */

By default (that is, unless you use "-W" at the command line) dcraw
will apply what amounts to a levels adjustment on your image, until 1%
of the pixels are solid white (clipped).  (I'm quoting an article I
wrote that annotates the dcraw c-code:
http://ninedegreesbelow.com/photography/dcraw-c-code-annotated.html#O1;
that article was the result of my quest to understand what raw
processing actually does).

Elle Stone

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[tosca]

2013/9/11 Gilles Caulier <[hidden email]>

WB = White Balance.

 

So what module are you refering to? And in BQM or in Edit?

Both. Look Raw demosaicing settings. There is a WB section.

Gilles Caulier

I got it, eventually! I didn't realize you were refering to the settings window...

As it is, the "auto-brightness" is checked; and probably has always been as I don't think I ever have changed it.

It might be the reason I'm so happy with Digikam JPEG rendering. :-)

Marie-Noëlle

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[Gilles Caulier-4]

2013/9/11 Elle Stone <[hidden email]>:
> In the digikam raw processing WB section there is "autobrightness"
> which sets the white level (Gilles, yes?), which is not the same as
> white balance. From the dcraw
> manpage,http://www.cybercom.net/~dcoffin/dcraw/dcraw.1.html

This settings is in WB section because is a post demosaicing
operation, and it's color relevant.

It apply a curve to image. See below.

>
> COLOR OPTIONS
> By default, dcraw uses a fixed white balance based on a color chart
> illuminated with a standard D65 lamp.
>
> -w Use the white balance specified by the camera. If this is not
> found, print a warning and use another method.
> -a Calculate the white balance by averaging the entire image.
> -A left top width height Calculate the white balance by averaging a
> rectangular area. First do dcraw -j -t 0 and select an area of neutral
> grey color.
> -r mul0 mul1 mul2 mul3 Specify your own raw white balance. These
> multipliers can be cut and pasted from the output of dcraw -v.
>
> OUTPUT OPTIONS
> By default, dcraw writes PGM/PPM/PAM with 8-bit samples, a BT.709
> gamma curve, a histogram-based white level, and no metadata.

^^^^ Auto-brightness is here, extended to 16 bits color depth...

It analyse histogram and compute a gamma curve automatically.

Gilles Caulier
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[Jean-François Rabasse-2]

On Wed, 11 Sep 2013, Marie-Noëlle Augendre wrote:

> I don't know how it does it, but each time I've needed a "quick" JPEG
> without actually "working" from the RAW, the BQM has given me a pretty good
> result that I didn't need to modify afterwards.
> For me, one more reason to never use RAW+JPEG as Digikam can do the job
> well and in an instant. :-)

Marie-Noëlle, would you please explain a bit your rationale ?
I'm not sure to understand.

You build automatic JPEGs, without actually working, from your RAW
files. Ok, that's perfectly clear.

But why do you say « one more reason to never use RAW+JPEG », as it
seems to me that keeping the out-of-camera JPEG is certainly the fastest
way to get quick (and excellent) JPEG.
(And often useful when traveling or in holydays, when you just want to
have a look at your images and have only a small laptop without any
software installed.)

Jean-François


PS: also, as Wolfgang wrote earlier, cf.

> The motivation of this post is my concern, that if I opt for shooting
> RAW only, I will not be able to get the "correct" jpg, in the sense
> the camera would have done it.

keeping original camera JPEG can never harm, in case one needs a help
or reference image, « correct » JPEG.
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[tosca]

2013/9/11 Jean-François Rabasse <[hidden email]>

On Wed, 11 Sep 2013, Marie-Noëlle Augendre wrote:

I don't know how it does it, but each time I've needed a "quick" JPEG
without actually "working" from the RAW, the BQM has given me a pretty good
result that I didn't need to modify afterwards.
For me, one more reason to never use RAW+JPEG as Digikam can do the job
well and in an instant. :-)

Marie-Noëlle, would you please explain a bit your rationale ?
I'm not sure to understand.

I always shoot in RAW, as I want to be in complete control of the rendering my pictures. But I keep quite many pictures that I don't treat, at least not immediately.

In some cases, say I need a picture of something I'm going to sell on eBay, or if I want to 'illustrate' something that has nothing to do with photography as itself, I find it very easy to pick up any picture from my base; if it still is in RAW format, Digikam allows me to resize (for publication) and convert it to JPEG in one go and less time than I need it to explain.  ;-)
And the resulting JPEG is perfectly good enough for this 'instant' need.

 

But why do you say « one more reason to never use RAW+JPEG », as it
seems to me that keeping the out-of-camera JPEG is certainly the fastest
way to get quick (and excellent) JPEG.

I'm not interested in quick/excellent/automated JPEGs. If the pictures are for my portolio, a show, or even for a customer, I always start working from a RAW.

RAW+JPEG takes more room on memory cards, more time to be recorded, and I would have to 'struggle' with twice more pictures to sort/organize on my computer.

 

PS: also, as Wolfgang wrote earlier, cf.

The motivation of this post is my concern, that if I opt for shooting RAW only, I will not be able to get the "correct" jpg, in the sense the camera would have done it.

keeping original camera JPEG can never harm, in case one needs a help
or reference image, « correct » JPEG.

I don't know what a 'correct JPEG' is. On my camera - probably on yours too - there are several pictures styles I can choose from, each of them can be customized with 3 o 4 different parameters, that can have at least 5 different values!, the result also depends of your instant choice about white balance, light enhancement, noise reduction, and whatever else.

When I'm on a shooting, I concentrate - and have enough to do! - on two things:

 - my subject and how I want to 'capture' it: composition, focal choice, and such

 - the way I want the camera to record it: mainly aperture/speed/ISO, and I do it in a manner that lefts me as many options as possible for 'after'.

The rest will have to wait for the post-treatment time: I have no interest in finding what would be the best parameters for the camera to produce a beautiful JPEG. It's completely lost time - and action - for me; and when 'the light' is here, believe me, I don't want to loose any time to use it as best a I can.

I think I should put a warning sign at the back of my van: beware of frequent stops! because it happens very frequently that I park in a hurry to shoot something on the spur of the moment, just because light is there. ;-)

Marie-Noëlle

PS: it was a bit exceptional (but I hope I'll have to do it again in the future) but on a recent assignment, I took between 800 and 1200 pictures per day on more than 12 days at a raw. In fact, it was time the tournament ends, because I had no more room left on my disks and cards, as I was too busy shooting to have time to sort the pictures. I don't even want to imagine what nightmare it would have been with twice more pictures...

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[Photonoxx]

Personally I only shoot in RAW.

If I choose a picture, there's no case where I need quickly a basic Jpeg to share/publish.

I never never do mass treatment, and develop RAW don't take much time in the whole treatment process.

Anyway, my D200, I'm pretty sure, embed a full resolution jpeg in metadata of the RAW file, may not the best fine quality JPEG, but very reasonable quality.

When I'm traveling, I use my tablet to copy my RAW on a portable hard drive and if I want, I use PhotoMate (or RAW photo mate I don't remember yet) to view my RAW files.



----- Mail original -----
De: "Jean-François Rabasse" <[hidden email]>
À: [hidden email]
Envoyé: Mercredi 11 Septembre 2013 13:48:10
Objet: Re: [Digikam-users] Questions on RAW conversion: Base curve


On Wed, 11 Sep 2013, Marie-Noëlle Augendre wrote:

> I don't know how it does it, but each time I've needed a "quick" JPEG
> without actually "working" from the RAW, the BQM has given me a pretty good
> result that I didn't need to modify afterwards.
> For me, one more reason to never use RAW+JPEG as Digikam can do the job
> well and in an instant. :-)

Marie-Noëlle, would you please explain a bit your rationale ?
I'm not sure to understand.

You build automatic JPEGs, without actually working, from your RAW
files. Ok, that's perfectly clear.

But why do you say « one more reason to never use RAW+JPEG », as it
seems to me that keeping the out-of-camera JPEG is certainly the fastest
way to get quick (and excellent) JPEG.
(And often useful when traveling or in holydays, when you just want to
have a look at your images and have only a small laptop without any
software installed.)

Jean-François


PS: also, as Wolfgang wrote earlier, cf.

> The motivation of this post is my concern, that if I opt for shooting
> RAW only, I will not be able to get the "correct" jpg, in the sense
> the camera would have done it.

keeping original camera JPEG can never harm, in case one needs a help
or reference image, « correct » JPEG.
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[Jean-François Rabasse-2]

Marie-Noëlle, thanks for the detailed explanations.

I had just missed something :)


On Wed, 11 Sep 2013, Marie-Noëlle Augendre wrote:

> I always shoot in RAW, as I want to be in complete control of the rendering
> my pictures. But I keep quite many pictures that I don't treat, at least
> not immediately.
> In some cases, say I need a picture of something I'm going to sell
> ...

« In some cases ... ».
Ok, so occasional processing only, not all the images.
That's what I first thought and why I was surprised about someone doing
what's already on the card. As you describe your way of working,
disk space and volume of images make sense, and your quick JPEGs come
only from time to time.

(I didn't intend to restart the good old debate about raw processing or
not, everyone has personal good reasons.)

Regards,
Jean-François




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