Base Curve tips or a good tutorial

rawprocessing
darktable
base-curve
(Alex Mozheiko) #1

Hi folks,
Does anyone know good Base Curve tutorial out there?
I’ve ben using DT for a while so there is NO need for introductory explanations. What I’m looking for is a deep explanation of this module. I apply it frequently on series of images - panoramas. Unlike Filmic it is very hard to control, has its benefits, yet there are many nodes, no eye-droppers nor value tables. Generic approach would be copy and paste the same setting through the series, however, with a shade in one image and the sun in another, I risk getting unbalanced overall exposure, cutting off histogram edges on either end. Thus, I’m looking to adjust each image, but in efficient way.
What exactly I’d like to know:
a) sign-posts, guidance on how to adjust the base curve to get the best point-to-point histogram
b) how to do this quickly, yet get the best of each image in a series
Any advice of yours would be greatly appreciated, and, if you know a good tutorial - drop it in the comments so later more people can find it.
:slightly_smiling_face:

#2

Harry is not someone who would do things “quick” but if you wanna go deep, there is ihmo almost no way around @harry_durgin

1 Like
(Alex Mozheiko) #3

Hehehe, watched it about two years ago :slight_smile: In this video Harry mimcs base-curves of the camera. My questions was about something different - how to render image correctly using the base-curve.

#4

Sorry got you wrongly. Reading all over I’d be on the wrong track again :rofl:

Seems I better shut up here :blush:

(Todd Prior) #5

I don’t think the base curve is where you need to go…There is now an auto exposure in the basic adjustments module…Its in version 2.7 which is not an official release but you can compile it…It will do autoexposure of the entire image or let you draw any size box on your image and it will auto expose based on that …works really well to give you a good histogram. You could likely also create some good presets image

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(Alex Mozheiko) #6

Oh, yes, that’s about what I’m looking for! And how does it correlate with the bse curve? Can the basic adjustments replace the basic curve?

(Andreas Schneider) #7

The base curve is from the beginning of darktable because it was brought over from ufraw iirc. However it isn’t really the best module. Normally you would use a tone curve instead of a base curve and if you have a color checker you can create a camera profile which includes a color LUT and curve for the camera.

However maybe the basic adjustments tool is doing a better automatic job as the curve is still fixed :slight_smile:

If you still want the curve, check my tutorial here on pixls.us how to create camera profiles.

1 Like
(Alex Mozheiko) #8

Thanks for this look into history.
IMAO base curve still has a lot of practical potential. What it lacks is an eye-dropper to see which regions are being adjusted. It, having an eyedropper, combined with those basic adjustments would bring a lot of clarity and comfort of usage - so one does not need to be clicking on different tools that come together first on the pipeline.

(Andreas Schneider) #9

Use a tone curve!

(Alex Mozheiko) #10

Would it consider the same input values as the basic curve ? AFAIK basic curve sucks in and processes data in RGB, while the tone curve has Lab and recently added RGB scales. I mean are you sure tone curve can dothe same job of rendreing post demosaic data?

(Andreas Schneider) #11

2.6.2 should use RGB mode for the tone curve by default …

#12

One thing I like the base curve module for is the Fusion option. Will Auto exposure be able to replicate those results?

The basic adjustment module really looks promising.

(Todd Prior) #13

Base curve is only really there to convert the linear sensor information in to log information which is how we perceive light as humans so its a conversion and starting point for your raw data. Its is camera specific in the sense that it is there to convert the sensor info of your camera and is the major way that it getsmodified to give you the jpeg version. You can play with it and use the fusion technique to help with dark images but the base curve only affect lightness where as the other modules and the tone curve work also with color…so they are what you should be using after you set the baseline with your tone curve…check out these for the background…IMO

2 Likes
(Chris E) #14

I like base curve for giving me a good starting point for my edit (I use it mostly when I’m quick-editing a large number of photos, say from a family holiday). Because the exposure module is before it in the pixelpipe, I like to adjust the exposure by dragging on the histogram until the image is no longer under/over exposed. That forms the start point for any subsequent edits.

(Todd Prior) #15

Wallie I have not used it yet extensively but it is quite handy. The big auto button is like spot white balance default ie it uses the whole image and adjusts the exposure and contrast…you have sliders for other elements like black point etc. but as with the WB spot mode it has a second mode where you can draw a box on any part of the image and it will use that data to adjust the histogram…so the subjects face or the fore ground or whatever you want…drawing the box on a few spots on the image lets you experiment and its very fast…some results will be over expose and some under but sometimes you hit on just the right spot and it just looks great…that’s how I have used it anyway…

(Alex Mozheiko) #16

@priort Thanks for this substantial reference.
So I guess I should stop caring about the base curve and, with the same and even more functionality, replace it entirely with the tone curve module. This solves my issue. Thanks a lot!

(Todd Prior) #17

Well I am sure there will always be a need to tinker with it and maybe even have 2 or 3 basecurve presets if you wanted but I think you are correct. Once you get a good basecurve that will set up your images consistently from your camera and then you can use the other modules in DT to address your images specific issues…there are so many tools and quite a bit of overlap so the more you go forward the more you will find the way that best works for you even though others may get at the problem using a different tool or setting…have fun …

1 Like
(Alex Mozheiko) #18

Thank you very much indeed!

(R) #19

If you’re interested, I made a tutorial on the base curve and how to create an orange and teal look with it. Here’s the link:

My tutorials revolve around artistic ways to use darktable as an alternative to Lightroom. In general, they do not revolve around technical explanations about a module. I just love editing images in any way I can.

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(Todd Prior) #20

Rico I think better to do this with the new rgb tone curve…esp as it comes after the input color profile…base curve is before that and so might affect results down the line in the pixel pipe…you need to be on a recent build to get that but then you don’t need all the extra base curve modules to try and achieve this…your approach with the separate colors if still valid for anyone reading…