Photoflow: luminosity masks issues


(Gustavo Adolfo) #1

Hi,
I’m trying to create the classic 9 luminosity masks in PF (instead of the three ones proposed by @Carmelo_DrRaw in his tutorial) .
However, I’m stuck on some issues:

  1. If I apply the same method as per the tutorial, I should only have to create more group layers, and for each groups mask, define curves that apply to a correspondent part of the histogram. For this, I divide 100 / 9 and get 11.1, which is the length between the right and the left points in the curve. The curves should be rectangles so that each group layer applies only to a part of the histogram.
    However, I’m not able to precisely adjust the points without distorting the curve, as per the image below:


    In this image, I’m trying to bring the up left and down left points to the in value of 10, but I’m not able to do so, either without distorting the leftmost part of the curve (see the the small peak?) or even change the in value of the left top point; curves-issue.pfi (11.7 KB)

  2. If I try to build the masks the gimp way, I have to create a group layer, then, in its mask, create a clone linking to the previous buffer layer, then a desaturate layer. However, desaturate doesn’t work (nothing happens):


    turning on the mask:

    The image I’m using is this linear rec2020 tif:https://filebin.net/sg3t4un5w6823n0o (still uploading as of now)
    pfi for the second case: desaturate-issue.pfi (10.4 KB)


(Gustavo Adolfo) #2

Humm… I think I have the answer to this: Anything inside the mask is already desaturated (it’s a greyscale image), so, I’ll try to assume that and proceed this way


(Carmelo Dr Raw) #3

Exactly, therefore the desaturate filter should not do anything. However, from your screenshot I see that the image gets corrupted, which is clearly a bug. I will fix that asap.

Concerning the luminosity mask, if you want to select a band in the luminosity you can do the following: add two points in the intermediate region, pull them to the top, and them move the two extreme points on the bottom axis and very close to the intermediate ones:

This will give you a sharp rectangular shape without any distortion.
The reason why you get distortions in your case is that the spline interpolation function tries to compensate the sharp transition. This does not happen if you directly move the extreme points…


(Gustavo Adolfo) #4

That’s it, thanks! ( luminosity-masks.pfi (87.2 KB)
)
For any newbie like me that haven’t read @Carmelo_DrRaw tutorial, these masks are generic, you just have to save, then load them, provided that right below you have a buffer layer. (The only caveat is that you have to go to each group mask and select the buffer layer you’ve just created as input to the clone layer. @Carmelo_DrRaw Couldn’t this be improved?)


(Andrew) #5

@gadolf, it will be interesting to see what you make of the street photo and how it compares with the others in the recent play raw thread and the scene-referred editing method.

I always thought that the more extreme curves are, and especially if they have corners, then the more likely unpleasant artefacts will result.


(Gustavo Adolfo) #6

Sure,

@RawConvert Could you please repeat this question in that thread? I think it belongs there.

@RawConvert Anyway, I don’t know the answer, but I suspect that the blur layer above the curves is to address the issue. From my experience on this exercise, I realized that tweaking the blur radius, as well as the mask slider, you can’t get rid off the artefacts.