Hallo Glenn,
uff, that sounds very interesting, but this way cannot and does not really want to go, that would overtax me very much. With all your help I will find my way into and with RT.
Many thanks for the info, now I know how little I know.
But RT still allows me to develop much better images than the camera can do internally. And I found pleasure in it.
Thanks to all
micha
Hallo Karlheinz,
yes, I knew this arrticle, and yet I studied it again today. Thank you very much for the hint.
I think the curves are very vivid and obey a very logical system - I even think I understand them quite well. In Gimp I almost exclusively use curves for brightness, contrast and colours.
RT offers the exposure sliders in addition to the curves and some also have builtin compression. I would like to understand these sliders better, because I suspect that they can do a very good job.
Many thanks for the hint.
micha
PS.: Schöne Grüße in den Schwarzwald
Had a little time between after work and wife coming home, so I collected a few screenshots of my previous curve endeavors. I have three examples, two images each, one with the curve, the other with the curve disabled so you can see the starting point.
First, the image from earlier in the thread. In this one, I chose to crush the lower-toned background to accent the flower, a lazy-man’s “layers”:
Now, a bit less aggressive application of a similar curve. This scene had patchy sunlight, so I wanted to emphasize that:
The above images could also be affected with a blackpoint setting roughly corresponding to the second curve control point. The difference would be that all the points to the left would just be zero; with the curve, there is still some definition in those pixels.
Not exactly to your question, but a recent change in my curve use. My new camera has a “highlight-weighted matrix” metering mode, which biases the matrix-calculated exposure to put the highlights back in the image range. I have it programmed into one of the function buttons so I can toggle back and forth; sometimes, the exposure doesn’t change because the scene is already “flat”. This is not the case in the example below, where the post-twilight dawn sky is clearly much brighter than the foreground, which is still in the mountain’s shadow. With these images, it is necessary to pull the shadows up, and the curve illustrated does that:
I’m still on the fence with this one (oh, a fence in the image, very punny!), and still trying to figure out how to best use this metering mode, but I’m pretty sure whatever I settle on will involve such a curve. For the readers familiar with ETTR, this metering mode uses the in-camera JPEG to determine clipping, so it doesn’t meet the ETTR sniff test. But the camera, Nikon Z6, has really good dynamic range so I’m just really counting on that “slop” to give me usable shadows, right now…
So @micha, I understand where you’re at with this, I was there just recently. But the ways of the curve are how all of these tonal manipulations are “laid flat”, so to speak; when I came to really understand the transfer function nature of the curve, I was able to “eyeball” so much more manipulation with it.
For what it’s worth… 
Hallo Glenn,
it is impressive that you can program your own software. I also understand your enthusiasm for using curves. In Gimp I only use the curves. But now I see the big advantage of finishing the photos with RawTherapee. Please note that I am in the process of familiarizing myself with RT. As long as I assume that RT is a very good converter, I don’t want to get familiar with another converter.
My aim is to make RT understandable to me as a committed beginner and later to all other users as well. And the best beginning seems to be the exposure and the brightness. I’m looking for the normal way, quite demanding, otherwise I wouldn’t need any raw development. What about the possibilities that RT offers the best way to correct a photo that is too dark or too bright? And then, how do you adjust a perfectly exposed image so that the mood makes it lighter or darker, according to your own taste?
If you, Glenn, want to give me and all other RT users a good introduction, we would be very happy. How something works with other software might be interesting, but sometimes it can be a bit confusing.
Many thanks for all the information and your efforts to make the screenshots for me. Your pictures, especially the one with the flower, are impressive, the mood is strong.
Thanks
micha
A curve is a curve, in most any software. The algorithm that draws the curve may vary, but the point is to put a set of control points on it that shape the curve to transform your image. That connection between your hand on the mouse and your brain is the same with any software that implements a control-point curve.
I wrote the software to do my raw processing the way I want, but I also keep in mind its use as a teaching tool. Go and try the things I illustrated with RT, you might need a few more (or less) control points, but if you shape the curve similarly it’ll do the same thing to whatever image you’re working. Oh, and I’m not thinking you should switch from RT; it’s a really good software to both show you the ropes while doing the stuff underneath you’re not ready to consider yet.
Thanks for the compliments on my images. I’ve been learning this stuff for about 3 years now, and it took quite a bit of work and frustration to get this far. I’m not even a “flower guy”; I yearn to make images during the winter, and they’re just sitting there in the house, all-so colorful in the afternoon light…
Hello afre
many thanks for this link that I know and appreciate. I like curves and also think I understand them well. In Gimp I only use curves.
RT has a lot of exposure controls and I think they work pretty well. It’s important for me to understand them. Not all at once, but bit by bit I want to understand the most important ones. Of course you can see immediately what they are doing, but I can’t always see exactly where they are already destroying tonal values or making them appear unnatural, especially if the next slider partially removes the errors.
I will try again to formulate my question:
Which sliders in the field of Exposure are indispensable? Which sliders are useful but not absolutely necessary, because another slider can do the function better? And finally, which sliders should better not be used (I assume Lightness, Contrast and Saturation in the Exposure area) if you want to achieve quality?
And the question: When to use “Black” for which action? Is there a replacement for it?
I also find the Slider Shadows/Highlighs very effective. Is there a better way to recover the light and dark tonal values above or below?
Sorry that I still have to ask these questions, probably I didn’t express myself well enough.
I thank all readers for their patience
micha
Hallo Karlheinz,
in RT there are a lot of curves. Which ones do you use? Please provide an exact name or a screenshot. I get very good results with the profile “Auto-Matched curve” in “Tone curve 1”. Do you then use the curve in “Tone curve 2”? Or do you go straight to Lab Adjustments? And what curve is there?
Many thanks in advance
Schöne Grüße und Danke
micha
I’m talking about the curve in the exposure tool. Take the 1st or the 2nd it shouldn’t matter. Then you don’t need the sliders in the exposure tool. How it works was shown in the link I provided.
Are those legacy tools listed in somewhere? Thanks for the great work btw!
It would make the work clearer and the learning easier, if there was such a list, in which the tools are noted, which are only available as a concession to old .ppt and which one better does not use nowadays. It would also make me very happy. Thanks in advance
Henri Matisse is credited with the remark, “I’ve been forty years discovering that the queen of all colors is black.” Maybe Norman Koretz knew that when he said on a tutorial webpage in the early days of digital post-processing that every image should have some black.
With their advice in mind, I turn on the RT clipped shadows warning and move the Exposure | Black slider until the image has some black.
https://live.staticflickr.com/65535/50846388928_1c267895de_o_d.jpg
