Creating B&W images

[godek]

I don't remember how or what it was. I learned this in a photography class in college and since have forgotten it. I think it was toning or maybe split toning or perhaps it was adjusting the contract but it had to do with using the eye dropper. I think the eye dropper was for finding the darkest(shadows) and lightest(highlights) areas and using that to get the perfect black and white for that particular image. I think this was done after the channel mixer with the contract tool then you used the eye dropper to get the measurements.

How do I do this in gimp? I am using gimp development version 2.9.8. Is there a tutorial somewhere?

[Ofnuts]

If you have the histogram you don't need the eyedropper. The histogram has its own dialog but is also displayed in the Levels and Curves. For instance with Levels:

   

[godek]

What does this do to the photo?

[rich2005]

It is all in here somewhere https://docs.gimp.org/2.9/en/gimp-tool-levels.html

Otherwise, use the 'eye' dropper to select the black and white values

[Ofnuts]

This make the black point completely black, the white point completely white, and stretches everything in between to fill the range. Easy enough to test by yourself... (the middle handle is used to adjust the "gamma").

[godek]

(12-31-2017, 09:03 AM)rich2005 Wrote: It is all in here somewhere https://docs.gimp.org/2.9/en/gimp-tool-levels.html

Otherwise, use the 'eye' dropper to select the black and white values

When I use the eyedropper how can I tell I am picking the right black or the right white?
Cause I've read you want to avoid picking one that is clipped in the histogram. is it highlights or shadows or both can be clipped??

BTW: What Distribution(s) of linux do you guys use?

[rich2005]

Quote:...When I use the eyedropper how can I tell I am picking the right black or the right white?...

That is your decision. All you can do is check the histogram before applying the level settings.

In this one my chosen point for white, looks ok, black however introduces a small bit of clipping. If really concerned then adjust the right slider and move over to include the start of the histogram. That was shown in Ofnuts first post.
You can also use the Histogram dock to get a real time display.



Which linux? I use Kubuntu 16.04 and a Gimp 2.9.9 portable (an appimage) Gimp 2.9 is a development version so I do keep the standard Gimp 2.8.22 as well.

[Ofnuts]

(12-31-2017, 10:28 AM)godek Wrote: When I use the eyedropper how can I tell I am picking the right black or the right white?
Cause I've read you want to avoid picking one that is clipped in the histogram. is it highlights or shadows or both can be clipped??

BTW: What Distribution(s) of linux do you guys use?

If the white/black points are clipped (ie, are already  0 or 255) then there is no point trying to improve the picture by moving them, you will only extend the clipped range.

The benefit of the histogram is that you can see how much you can cut on both ends to stretch the midtones. In the histogram I posted, setting the white point to 220-230 doesn't lose very many pixels, while at the other end you have little margin around the black point.

Using (K)ubuntu 16.04.

[mholder]

https://www.youtube.com/watch?v=wv-SPlX3...i9TG6GrV6s
This guy's playlist videos on levels and curves are the best I have ever seen.  I already knew most of this stuff, but he most clearly explains all the features.

Start first with levels sliders and then click the 'edit these settings as curves' button to fine tune the curves, which can add points with the eyedropper that can be adjusted with the keyboard arrows keys.  For a long time I used levels and curves but did not realize how easy the were to fine tune.

[godek]

How do I know if am image is clipped in a histogram?