I just added a function to GHS (Generalized Hyperbolic Stretch).
This allows you to shift the histogram towards the midtones (midtones balance). This algorithm is particularly useful if the image is very dark or bright. In fact, it acts like a midtone balance.
The system takes into account the value of ‘Stretch factor (D)’.
It is essential to adjust the values of ‘Stretch factor D’ and ‘Local intensity (b)’.
Only available for the ‘RGB Standard’ and ‘RGB Luminance’ methods.
This action can be complemented by the ‘Midtones’ slider in ‘Stretch Regularization & Midtones’.
I’m just trying this new feature out, and adding a global spot, this seems to work well on this shot… except I cannot see the spot centre. Then, if I add a normal spot, not only can I not see the spot centre, I cannot adjust the size/shape… there is nothing to click/select… see this screen shot with a normal spot visible via the scope tool, noting the lack of centre and edges.
I can go back to the last dev version, 5.12-372, but thought I’d highlight this. I think I have selected everything correctly in preferences… Perhaps I have missed something out??? Any advice would be appreciated.
‘Normally,’ this new feature doesn’t affect the GUI (except for the slider and the checkbox). So, no impact on the visibility of the Spots.
I tried it on several images to simulate what you did. Everything seems to be working normally. But? But? Anything is possible. That’s the purpose of these pull-request testers: to see what works and what malfunctions.
If the image isn’t confidential, could you send me the RAW and PP3 files?
To help me find the cause, can you confirm the operating system (Windows, I think? ot Linux… )?
Personally, I work with the versions I compile myself (Windows 11 - minw64 or Linux Ubuntu 24.04 LTS).
Thanks for the response… appreciate your time and thoughts. I tried a downloaded play raw file and it was the same. So I uninstalled the merge (and everything else RT related) and downloaded the 5.12-372 dev version in full and installed that… My spots are back! so to speak… Anyway, all fixed my end.
I quite like the MTF option, it seems to give a more subtle approach to GHS Stretch and Local Intensity… more balanced I think/feel. I’ll continue to use/try this new option.
I still have artifacts/weird colour shift when using the CAM16 Colour Appearance and lighting in Advanced… the RGB section, Control cage for brightness (any colour) seems to pull colours out of gamut with only the smallest of adjustments… So I am tending to steer clear for now. This is not a bother for me, I use other tools to adjust brightness (selective editing; normal spot; Colour & Light for example).
I’ve made a few modifications to the Michaelis-Menten (MM) algorithm. These modifications don’t change the algorithm itself (which is very good), but aim to reduce the complexity of the choices: faced with a poorly exposed image, what should you do? What should you do when faced with a multitude of choices… which are actually quite limited in the case of MM.
I made 2 changes, relating to the information for ‘understanding’, and to try to help reduce the complexity of multiple choices.
Information
I have entered two values that are displayed below ‘Subtract linear black’ and ‘Linear dynamic range’
RGB max: This value is measured at the end of ‘MM’. It is normally in the range [0 1]. Exceeding the upper limit (for example, 1.22) indicates that the data is outside the limits of the Working Profile (by default Rec2020 – which is practically the largest possible color space without using imaginary colors – those that our eyes cannot perceive). Therefore, regardless of the choices made in the ‘MM’ settings, it is imperative that ‘RGB max’ be set to a maximum of 1.
Middle grey: This value represents the arithmetic mean of the data at the end of ‘MM’. It is given as a guideline, and its value is not fundamentally important (purists will say 0.18, but if it’s at 0.08 and you’re happy with the image, it’s not a ‘defect’), because this average takes into account the values of the Black point ‘Subtract linear black’ (BP) and the White point ‘Linear dynamic range’ (WP). Anyone who can predict what happens when the WP is greater than or much greater than 1 (for example, 4) is a genius (which I am not). This indicative value will allow you to ‘understand’ what you are doing. If, for example, the image seems too bright (or too dark) – either subjectively or with the help of the histogram – you might be tempted to first and foremost use ‘Exposure (Ev)’ to change this ‘Middle Grey’… I’m not saying you shouldn’t use it, but in tricky cases where the WP is high, it will often be preferable to use ‘Knee Strength (K)’ and ‘Output Scale’, which are the two true components of the ‘MM’ algorithm.
The addition, as in GHS, of the ‘Midtones Transfer Function (MTF)’.
This feature is only available if ‘Linear Dynamic Range’ is enabled… That is to say, the data, including for images where the white point is very high, is theoretically within the range [0 1], therefore within the Working Profile.
This ‘MTF’ allows you to balance the midtones – a kind of ‘midtones
balance’.
Once again, thank you to @jdc for valuable information, application and contribution to this tool in RT. I’ll head over to GitHub as soon as I can… About a week… And try these new developments out.
