Documentation for the base curve module from darktable 2.3 (links updated)

[kuerbis]

Hello,

if I remember right, harry durgin talks in one of his videos about the settings of the base curve module from darktable version 2.3. - does somebody know, in which video?

[yteaot]

http://weeklyedit.com/additional-thoughts-camera-profiling/

[Claes]

And/or these ones?
http://weeklyedit.com/basecurves/
http://weeklyedit.com/playlist/?module=Base%20Curve

[kuerbis]

Thanks!

[Claes]

Addendum: with joy I have noted that the links I gave above are popular.
Unfortunately, weeklyedit.com seems depressed (= down) these days. ping @harry_durgin

However, you will be able to find many of Harry’s tutorials here https://www.youtube.com/watch?v=LufwQZx01gk

Have fun!
Claes in Lund, Sweden

[asn (Andreas Schneider)]

Don’t use the basecurve tool. Create a camera profile instead! A tutorial for that will be available on pixls.us soon.

[Gobo (Peter)]

Is “camera profile” already implemented in DT? Basecurve has preset “Panasonic like” but I guess it was created for particular model and when I apply it to my GX7 photos first thing I notice is that photos need circa +0,3EV exposure as they are dark. If I can make such a profile for GX7 please let me know, I’ll try to create one and send it to developers.
edit: in links above there is video by @harry_durgin with tutorial how to create “basic curve” profiles for each ISO setting. Unfortunately, it’s done on linux so I can only provide samples to create profiles.

[asn (Andreas Schneider)]

Hi Gobo,

yes, camera profiles are supported by darktable! The basecurve has been generated for Panasonic cameras in general. If you want a profile for your camera, you should create a camera profile and share it.

I’m sorry, but Harry his videos are incorrect.

Please read PIXLS.US - Profiling a camera with darktable-chart

[Hevii_Guy]

Andreas, I’m trying to work through the process of profiling my camera. Whereas I truly appreciate your in-depth article, there are a few things which aren’t very clear. Perhaps you can clarify?

Let’s start off with why you feel that Harry Durgin’s video tutorial is incorrect. I’m sure that by explaining this your answer will likely augment that which is already in your article! More knowledge is a good thing. It will probably fill some of the current holes in the general level of understanding.

Let’s move on…

I’m using the Color-checker Passport. You note that it’s important to have an L-value of 96 for the neutral white patch. I’ve noticed that this is dependant upon exposure.

• What does one do if none of the Raw photos in the set of ever-increasing ISOs are exposed so as to give this value?
• If say, only the ISO 100 exposure produces this value but the subsequent shots do not, what is one to do?
  (The L-values on all of my shots are unique).

You say “disable most modules, especially the base curve!..”.

• What do you mean “most”?
• Which ones can remain?
• Which ones other than the base curve must not be enabled?

You mention that one must create a custom white balance before taking the profile shots. In the instructions you include “If your camera has a custom white balance feature…”

• If the camera doesn’t, what is one to do?
• Like most, mine has a custom white balance feature. However, following from the above, can one correct the white balance in post by using dt’s White Balance module without compromising the profiling workflow?

With regards to darktable-chart, you say “Now it is time to start darktable-chart”…

• I think that more than a few people would appreciate greater details explaining how this is to be done from the Command Line
• Am I correct to infer that this functionality is not available from the “regular” darktable version and that one must roll one’s own?
• If your answer to the above is “yes”, the next question posed to the developers is “why”. I would think that self-compiling is well beyond the abilities of many of dt’s users, particularly if they’re not running Linux!

I’ll finish-off with a personal observation: I don’t give a rat’s butt about what the OEM’s designers feel that my unprocessed fotos should look either in-camera or prior to post. Hence, I don’t care if my fresh RAWs don’t look like the OEM’s jpegs. I simply want my baseline to reflect (hah: a pun!) real-world colours. From there it’s only up to me to begin doing funky things

[asn (Andreas Schneider)]

Let’s start off with why you feel that Harry Durgin’s video tutorial is incorrect.

• Harry assumes an incorrect L-value (as in Lab) for the neutral gray patch for the ColorChecker Passport!
• The setup for shooting the target is very bad.

• What does one do if none of the Raw photos in the set of ever-increasing ISOs are exposed so as to give this value?

Redo the photos with better conditions!

Quoting the article: If the value displayed in the color picker module matches the L-value of the field or is close (+0/-2. This means L=94 to L=96 is acceptable), give the RAW file and the corresponding JPEG file 5 stars.

• If say, only the ISO 100 exposure produces this value but the subsequent shots do not, what is one to do? (The L-values on all of my shots are unique).

Then only use the ISO 100 exposure which is fine to apply for other ISO values too.

You say “disable most modules, especially the base curve!..”.
What do you mean “most”?

None is the best (beside the once you can’t disable )

• Which ones can remain?

Orientation; Crop & Rotate, Lens Correction (if required)

• Which ones other than the base curve must not be enabled?

All which manipulate the image in color or tone. Orientation and Crop&Rotate are fine.

Quoting the article: You can also crop the image but you need to apply exactly the same crop to the RAW and JPEG file! (This is why you use a tripod!)

You mention that one must create a custom white balance before taking the profile shots. In the instructions you include “If your camera has a custom white balance feature…”

• If the camera doesn’t, what is one to do?

Auto White Balance (AWB)

• Like most, mine has a custom white balance feature. However, following from the above, can one correct the white balance in post by using dt’s White Balance module without compromising the profiling workflow?

No, you can’t! You created a JPEG which is a developed picture with the applied White Balance your camera used!

With regards to darktable-chart, you say “Now it is time to start darktable-chart”…

• I think that more than a few people would appreciate greater details explaining how this is to be done from the Command Line

I don’t see why. You don’t need a terminal to start darktable-chart.

• Am I correct to infer that this functionality is not available from the “regular” darktable version and that one must roll one’s own?

If it is not packaged, contact the packager and report a bug!

Hence, I don’t care if my fresh RAWs don’t look like the OEM’s jpegs. I simply want my baseline to reflect (hah: a pun!) real-world colours.

Then match against a CIE file.

Andreas

[P.S. I’ve sent a request to update the article on pixls.us]

[Hevii_Guy]

Thanks, Andreas! It’s becoming more clear now. Yet, the waters are still a bit turbid …

@asn

Auto White Balance (AWB)

• Like most, mine has a custom white balance feature. However, following from the above, can one correct the white balance in post by using dt’s White Balance module without compromising the profiling workflow?

No, you can’t! You created a JPEG which is a developed picture with the applied White Balance your camera used!

Surely this doesn’t matter if all one wants to do is match against the CIE file, right? Furthermore, if this is one’s end goal, there isn’t really a need to shoot any jpeg files, correct?

@asn

You don’t need a terminal to start darktable-chart

Great! Alas, I’m not quite sure how to run it . Any hints?

[asn (Andreas Schneider)]

Surely this doesn’t matter if all one wants to do is match against the CIE file, right? Furthermore, if this is one’s end goal, there isn’t really a need to shoot any jpeg files, correct?

I’m sure you will find out and then can report back

Great! Alas, I’m not quite sure how to run it

Looks like it doesn’t come with a desktop file, which is worth a bug report …

Open a Terminal and type: darktable-chart

If this doesn’t work, blame your packager

[Hevii_Guy]

Sorry; I’m not quite sure about the following either…

@asn

You mention that one must create a custom white balance before taking the profile shots. In the instructions you include “If your camera has a custom white balance feature…”

• If the camera doesn’t, what is one to do?

Auto White Balance (AWB)

Hmm… I don’t think that it’s a good idea to trust Auto Anything! If the camera’s AWB isn’t indicative of the real world and one’s goal is to produce a real-world profile, then it seems that the poor suckers who are without the ability to customise White Balance, are left holding the short stick. With this in mind, I’m hoping that what I think that Pascal de Bruijn is doing is, in fact, acceptable.

@asn

• If say, only the ISO 100 exposure produces this value but the subsequent shots do not, what is one to do? (The L-values on all of my shots are unique).

Then only use the ISO 100 exposure which is fine to apply for other ISO values too.

So, are you saying it’s okay to use incorrect L-values on the other photos? Or, are you saying that one must just use the ISO 100 profile regardless of the actual ISO conditions of other photos? The latter kinda defeats the purpose of the exercise, doesn’t it?

@asn

• What does one do if none of the Raw photos in the set of ever-increasing ISOs are exposed so as to give this value?

Redo the photos with better conditions!

Wow. Seems to me that this could be a day-long exercise of chasing one’s tail in an on-going effort to tweak untold variables until one arrives at an acceptable L-value. But, if this is the price that one must pay, well, this is what will be done…

[Hevii_Guy]

@asn

Surely this doesn’t matter if all one wants to do is match against the CIE file, right? Furthermore, if this is one’s end goal, there isn’t really a need to shoot any jpeg files, correct?

I’m sure you will find out and then can report back

Well, I was kind of hoping that you as the apparent ‘expert’ would shed some light onto this, Andreas. Hence the request for verification of what are merely my assumptions

[paperdigits (Mica)]

I choose to look at him as adding what he knows to our collective knowledge base. You can do the same.