Thank you for the detailed explanation. I did this earlier today, just guessing what to do. Now I have real information to follow, and a few questions.
First screen - no issues.
Second screen - I will select my ASUS monitor, as I don’t want to mess around with the iMac itself. Your example screen a the left says to use PHOTO on this screen, but you have CUSTOM. I don’t understand the details of the three things you are setting - do I just copy your information for my own display? I imagine we are setting the white point to be the small white area with the tiny dot in your image. Do I move that around, or does it just go to the white point by itself, and that’s where the first data comes from? Luminance - I assume I should use your value, and ditto for Tone Response Curve? …so much I don’t know - never needed to know, although I guess I should have learned this long ago.
Then I go to “measurement”. On your screen you checked "Adjust brightness, contrast, and RGB gains manually. For now, can I let it to this automatically? For you, it says to go into System Preferences | Monitors, but I have no such control in my System Preferences Window. I’ll make a screen capture and post it:
There is no automatic brightness for my ASUS, only for my iMac, but I’m not going to mess with the settings on the iMac. I will do my image editing on my 27" ASUS.
Note: I do have lots of manual controls on the bottom of my ASUS, so if I can find the old manual, maybe I can adjust the brightness later.
Thanks for the time it took to put all that together. They ought to have sent me a user’s manual with the device, explaining all this in detail. All I got was a simple setup guide. 