Welcome to the Canon forum!
So that the Community can help you better, we will need to know the model number you are using. Also, which operating system is running on your computer (i.e. Windows or macOS and which version) Any other details you'd like to give will only help the Community better understand your issue. If this is a time-sensitive matter, click HERE search our knowledge base or find additional support options HERE
Which model number? Sorry, I'll take a chance at this.
Shooting with 6D Mk II, Processing with DPP4, V 220.127.116.11, on macOS V 10.13.6.
I am shooting single exposure StarScape or Landscape Astrophotography at ISO 3200-12800, exposed for 60-150 seconds, ultra-wide angle, wide open, mounted on a star tracker, and then processing to create a sense of standing under the ultra-dark skies where I took the pictures.
Here is a link to the tone Curve section in the DPP manual:
Here is a YouTube tutorial. He discusses the tone curve around the 34 minute mark.
12/05/2023: New firmware updates are available.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.